This report is a summary of the projects undertaken by the Beneficial Insects Laboratory (BIL) of the Plant Protection Section of the North Carolina Department of Agriculture and Consumer Services during 1997. The BIL is actively engaged in classical biological control projects, in which the natural enemies of pest insects and weeds are released in the environment with the goal of stabilizing pest populations below their economic threshold. The "other half" of the Beneficial Insect Lab is the Apiary Inspection Program, supervised by Don Hopkins, State Apiarist. He, along with 5 field inspectors cover North Carolina, provide inspection services to the beekeepers of the state as well as demonstrations and educational talks to the general public. The Apiary program expanded this year, with the directive to maintain the health and genetic stock of honey bees in NC. Enhanced funding from the legislature provided the means to furnish a laboratory and hire a technician to provide quality assurance for our disease control methods and determination of Africanized honey bees. We are grateful to the NC State Beekeeper=s Association and its president, Irvin Rackley for their efforts in obtaining this funding. In October we were saddened by the loss of Mr. James (Jimmy) F. Greene, Jr., the first Biological Control Administrator at NCDA. He held that position from 1976-1987, but began his career at NCDA as an entomologist in 1949. He retired from full time service in 1988, but immediately began working as a part-time apiary inspector and served in that capacity until his death. We are grateful for his contributions to the state and he will be missed. The cooperative extension service, faculty, and staff of North Carolina State University, USDA-APHIS and ARS all played roles in the implementation of our programs during 1997. We are grateful for the cooperation of other members of the NCDA Plant Protection Staff, including Support Services, the statewide field staff under the supervision of John Scott, Dan Wall, and Lloyd Garcia, and the identification service provided by NCDA taxonomist Kenneth Ahlstrom. Implementation of our 1997 programs included release of a total of 15,410 beneficial insects; some were relocations within the state and others were introductions from out of state. Cooperative work with USDA-APHIS-ARS for cereal leaf beetle and ash whitefly control continued during 1997. Studies on the biology and establishment of the ash whitefly and its parasitoid, Encarsia inaron continues, as does research on the adventive predator Harmonia axyridis. Thistle biological control continued in 1997, and a new weed biological control program was initiated on Japanese knotweed (Fallopia japonica), with the assistance of the Forest Health Technology Enterprise Team of the US Forest Service. Another new project is the biological control of fall cankerworm (Alsophila pometaria) in the city of Charlotte. The Quarantine Facility housed at the laboratory has been used by entomologists from NCSU as well as by our own personnel. Janet Shurtleff, Ph.D., serves as the Quarantine Officer, and welcomes inquiries about the facility. Personnel of the Beneficial Insects Laboratory We request that permission from the author be obtained if the use of information in this document is for publication purposes. Where trade names are used, no discrimination is intended, and no endorsement of one product, to the exclusion of other similar products, by the North Carolina Department of Agriculture is implied. A table of contents follows. K.A. Kidd and C.A. Nalepa
Total R. conicus: 9,047
Total T. horridus: 1,127
Total U. stylata: 520
Total U. cardui: 51
Total E. inaron: 4,665 All releases were local redistributions within Raleigh, Wake Co. GRAND TOTAL: A total of 15,410 insects were released in North Carolina during 1997; 5 species of natural enemies onto 4 hosts. * Indicates releases made with Richard McDonald of Symbiont. NCDA&CS Beneficial Insects Laboratory
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| ID# | SPECIES | FAMILY | STAGE | # | ORIGIN | STATUS |
|---|---|---|---|---|---|---|
| Q95-1 | Tiphia popilliavora | Tiphiidae | pupae | 190 | China | Part of shipment emerged in quarantine and was preserved, remainder is still in pupal stage. |
| Q97-1 | Blattella germanica | Blattellidae | adults\nymphs | - - - | Japan | Insects received in this shipment died in quarantine. |
| Q97-2 | Lymantria dispar | Lymantriidae | larvae | 819 | NC | Insects dissected and autoclaved. |
| Q97-3 | Encarsia inaron | Aphelinidae | pupae | 50 | France | Insects received in this shipment died in quarantine. |
| Q97-4 | Tetrastichus julis Diaparsis temporalis Lemophagus curtus |
Eulophidae Ichneumonidae Ichneumonidae |
pupae pupae pupae |
100 500 500 |
France/ Greece |
Part of shipment emerged in quarantine and was preserved, remainder is still in pupal stage. |
| Q97-5 | Trichogramma exiguum* | Trichogrammatidae | larv./pupae | 15m | France | Released from quarantine. Insects originally from U.S., reared in France, and shipped back for release in NC. |
*There were 11 shipments of this species: 7 contained 1,000,000 each and 4 contained 2,000,000 each.
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ABSTRACTS
Cereal Leaf Beetle
Work on this project, done cooperatively with USDA, APHIS continued in 1997. Insectaries for rearing larval parasitoids are located in the western Piedmont of NC near Salisbury and in the coastal plain near Plymouth. Tetrastichus julis a larval parasitoid that has been present in NC for 19 years continues to be recovered at the Piedmont insectary, but has not become established in the coastal plain. A foreign exploration trip to France was undertaken in May, and 2400 CLB pupal cells were collected. These are currently being held in the NCDA Quarantine Facility until emergence of parasitoids in the spring. The purpose for this collection was to obtain parasitoids from a climate similar to that of NC.
Flowerhead Weevil for Musk Thistle Biocontrol
Releases of the flowerhead weevil Rhinocyllus conicus (Coleoptera: Curculionidae) were continued for biological control of musk thistle (Carduus nutans). A total of 9,047 R. conicus adults were released in seven counties (Nash, Lincoln, Gaston, Cleveland, Catawba, Orange, and Wake). Releases were made in cooperation with farmers, North Carolina Cooperative Extension Service agents, North Carolina Department of Transportation personnel, and with Richard McDonald of Symbiont. Weevils were released at musk thistle infestations in pastures, at dairies, and along highway rights-of-way. One thousand one hundred flowerhead weevils were shipped from Tennessee for release in North Carolina; the remaining weevils were collected from an established population in Franklin County. Beginning in late June, the weevils for release were reared from musk thistle flowerheads where eggs were laid earlier in the spring. These summer releases, though known to be less efficient than spring releases for weevil establishment, were made because a large supply of emergent adults was readily available. Parasitism of R. conicus was low (<1%), with the following parasitoids recovered: Bracon mellitor (Say), Bracon sp., Nealiolus curculionis (Fitch) (Hymenoptera: Braconidae); and Neocatolaccus sp. (Hymenoptera: Pteromalidae). R. conicus is now widely distributed in parts of western and central North Carolina and, where the weevil is present, we expect R. conicus to continue to contribute to the reduction of musk thistle populations. The musk thistle population at our long term evaluation site continued to decline. Populations of R. conicus and the rosette weevil Trichosirocalus horridus (see below) are now such that private individuals can effectively collect and redistribute the weevils at a local level. Continued redistribution of R. conicus and T. horridus by the Beneficial Insects Laboratory will concentrate on establishing the weevils in new areas and at roadside musk thistle infestations.
Rosette Weevil for Thistle Biocontrol
Releases of the rosette weevil Trichosirocalus horridus (Coleoptera: Curculionidae) were continued for biological control of musk thistle, bull thistle (Cirsium vulgare), and plumeless thistle (Carduus acanthoides). A total of 1,127 T. horridus adults was released in four counties (Nash, Lincoln, Gaston, and Cleveland). Six hundred rosette weevils originated in Tennessee; the remainder was collected in North Carolina.
Urophora stylata for Biological Control of Bull Thistle
The flowerhead-infesting fly Urophora stylata (Diptera: Tephritidae) was obtained from the Oregon Department of Agriculture for first-time release in North Carolina for biological control of bull thistle (Cirsium vulgare ). U. stylata larvae produce galls in bull thistle flowerheads which decrease seed production. A total of 520 adult U. stylata adults was released in June and July at three sites (one site each in Lincoln, Nash, and Franklin Counties). Flowerhead galls were found in October at all three release sites, providing evidence that U. stylata has become initially established in North Carolina. Release sites will be studied in coming years to monitor U. stylata populations and to evaluate the fly's effects on bull thistle. Additional flies will be obtained from the Oregon Department of Agriculture for release in 1998 in North Carolina.
Urophora cardui for Biological Control of Canada Thistle
The fly Urophora cardui (Diptera: Tephritidae) was obtained from the Oregon Department of Agriculture for first-time release in North Carolina for biological control of Canada thistle (Cirsium arvense). U. stylata larvae produce stem galls on Canada thistle, thus weakening the plant. Fifty-one U. cardui adults were released in July at a single site in Alleghany County. In October, no evidence of U. cardui establishment at the release site was found. This release site will be monitored next year in light of the possibility that U. cardui establishment went undetected this year. Additional flies will be obtained from the Oregon Department of Agriculture for release in 1998 against Canada thistle in North Carolina.
Permission to Release Psylliodes chalcomera for Biological Control of Musk Thistle
After submitting supporting documentation to state and federal agricultural regulatory authorities, the Beneficial Insects Laboratory received permission to release in 1998 the leaf-feeding beetle Psylliodes chalcomera (Coleoptera: Chrysomelidae) in North Carolina for biological control of musk thistle. P. chalcomera beetles will originate in Italy, and will be distributed by the USDA's Agricultural Research Service to cooperating state agencies depending on available numbers. It is believed that P. chalcomera will complement the effects of the flowerhead weevil and the rosette weevil for biological control of musk thistle.
Potential for Biological Control of Japanese Knotweed
Japanese knotweed (Polygonum cuspidatum) is an invasive exotic weed of east Asian origin that infests roadsides and stream banks in North Carolina. This plant is presently under investigation by the Beneficial Insects Laboratory as a potential target weed for classical biological control in North Carolina and elsewhere in North America. We hope to cooperate with the International Institute of Biological Control in the United Kingdom and other agencies to evaluate and import natural enemies for knotweed biocontrol. Surveys were conducted in 1997 in North Carolina to document the distribution of Japanese knotweed and the closely related, but less abundant, Sakhalin knotweed. Vigorous Japanese knotweed populations were found from the mountains to the eastern Coastal Plain. As expected, Japanese knotweed has few natural enemies in North Carolina. Some knotweed populations, however, were found to be attacked by Japanese beetle and some knotweed plants had pathogen-like symptoms on leaves. With financial support from the U.S. Forest Service's Forest Health Technology Team, work to further the initiation of a biological control program against Japanese knotweed will continue in 1998.
Investigation of Biological Control for Fall Cankerworm in Charlotte
The city of Charlotte has experienced a serious outbreak of the defoliating caterpillar Alsophila pometaria (Lepidoptera: Geometridae) for approximately ten years. Most affected are willow oaks of residential areas. In contrast to most outbreaks in forest situations where fall cankerworm populations have declined naturally within five years, fall cankerworm has persisted in Charlotte. In cooperation with Don McSween, Charlotte city arborist, we are attempting to establish an aggressive strain of the egg parasitoid Telenomus alsophilae (Hymenoptera: Scelionidae) in Charlotte for biological control of fall cankerworm. Also, we are investigating the biology of fall cankerworm in Charlotte, as well as other tactics for fall cankerworm biological control.
Ash Whitefly
The NCDA's ash whitefly biological control program began in Raleigh in the fall of 1994 with the release of Encarsia inaron, a minute parasitic wasp which controlled ash whitefly in California. Evidence of parasitization was detected on a leaf collected on 30 September 1997. Sites in Sampson, Onslow, and Rowan counties were searched for ash whitefly; however, none were found in these locations. A total of 4665 E. inaron adults was released in Wake County in 1997. Work is underway to obtain and release a variety of E. inaron that is native to a cooler area than the strain presently in Wake County.
Pitcher Plants
Pitcher plants function as pitfall traps for insects attracted to extrafloral nectar. The only study to identify insect victims to the specific level was by Wray and Brimley (1943 - Ann. Entomol. Soc. Amer. 36: 128-37) in North Carolina. We followed up on their study, using pitcher plants to sample lady beetles over the course of two seasons (May-June-July) in 1996 and 1997. Results indicate that introduced species (C. septempunctata and H. axyridis) comprised 49.2% of collected lady beetles in 1996-1997. Cycloneda munda shows the greatest difference from historic data; it ranked #2 (32.4% of catch) in the 1930's, but #5 (3.6% of catch) in the 1990's. In both 1996 and 1997, no C. septempunctata or H. convergens were collected after the end of June, suggesting aestivation in these species. Both males and females are attracted to extrafloral nectar. Of five plants tested, Sarracenia flava was most attractive to Coccinellidae.
Gypsy Moth - Entomophaga maimaiga
A total of 819 gypsy moth larvae were collected weekly in three collections during May 1997. Larvae were collected from burlap bands on trees where soil infested with Entomophaga maimaiga was distributed in November 1996. Most of the larvae died of stress or emerged as healthy adults (86%), 14% of the larvae died of diseases and parasitism (2.8% of total were parasitized). Infected larvae were collected on all dates. Nearly twice as many infected larvae were collected 28 May compared to 14 May.
PROJECT REPORTS
Cereal Leaf Beetle Parasitoid Insectary Program, 1997
K.A. Kidd and J. M. Caldwell
The cereal leaf beetle, (Oulema melanopus (L.)) (CLB) (Coleoptera: Chrysomelidae) a pest of small grains, has been present in North Carolina since 1977. The species is native to the Palearctic regions and was first identified in the United States in Michigan in 1962, and gradually spread south and eastward (Haynes and Gage 1981). The first infestations of CLB found in NC were in 19 counties primarily along the Virginia border. Its range has since expanded to include all of the grain growing regions of the state. This insect can cause severe damage to the leaves of wheat, oats, barley and other cereal crops; when heavy feeding occurs, grain yields may be reduced.
After the insect was discovered in the US, quarantines were enacted to slow its spread, and eradication was attempted. These efforts were unsuccessful, and a biological control program began in 1963. Parasitoids were collected in Europe, and parasitoid nurseries (or field insectaries) were established in Michigan and other midwestern states by the late 1960's, and field days were held to distribute parasitoids to extension personnel and farmers from the area. One species of egg parasitoid and three species of larval parasitoids were originally imported from Europe by USDA, and all have been released in North Carolina. Anaphes flavipes (Foerster) (Hymenoptera: Mymaridae) (the egg parasitoid), was released as early as 1978. This species disperses well and is not reared in insectaries; it is released and allowed to spread on its own. Three larval parasitoids, Tetrastichus julis (Walker) (Hymenoptera: Eulophidae), Diaparsis temporalis Horstmann (Hymenoptera: Ichneumonidae) and Lemophagus curtus Townes (Hymenoptera: Ichneumonidae) have also been released.
In 1978, the first parasitoid releases were made in North Carolina, and a field insectary program, similar to the program in Michigan, was started in the fall of 1987. In 1997 insectaries were located at the Tidewater Research Station near Plymouth, NC A&T Farm near Greensboro, Oxford Research Station near Oxford, and the Piedmont Research Station near Salisbury. The Piedmont insectary is the only one which has had perennial populations of CLB and Tetrastichus julis; T. julis has been recovered at both Oxford and the A&T farm, but none have ever been recovered at Tidewater.
Materials and Methods
Descriptions of the parasitoid insectaries may be found in previous reports (Kidd and Bryan 1993, 1994). Although each insectary follows a different planting design, they all consist of two or four plots, each of which is divided into two or more subplots. All have fall wheat followed by spring plantings oats. No-till planting methods are used throughout.
Beginning in late March or early April, insectaries were monitored every 4-10 days. Presence of CLB adults in the early spring was determined using sweep net samples; after eggs and larvae were detected, the presence of adults was noted during visual inspection of the plants. To determine population densities of the eggs and larvae, three samples of one square foot each were taken in each subplot. Each sample consisted of counts of all eggs and larvae on 20.5 inches of small grain row, and the three counts were averaged for each subplot. After larvae were detected in the field, samples of eggs and larvae were removed and examined for the presence of A. flavipes (eggs) or larval parasites. Samples from Tidewater and Piedmont sites were shipped to Niles, MI for determination, and a small subsample of these were processed at NCDA along with CLB from the Oxford insectaries. Eggs were arranged in small petri dishes and held for the emergence of adult parasitoids; larvae were dissected for parasitoid eggs or larvae by K.R. Ahlstrom, NCDA Plant Industry taxonomist.
Results and Discussion
Populations of cereal leaf beetle were high at the Piedmont Insectary and low at the Tidewater and Oxford insectaries (Table 1). At the Piedmont Insectary, the highest egg density was found on 8 April in all plots. Highest larval populations occurred between 2 and 12 May. At the Tidewater insectary, highest egg populations occurred between 2 and 9 April. Larvae populations developed 1-2 weeks earlier on the wheat which was planted earlier than the oats.
The larval parasitoid T. julis persists at the Piedmont insectary, but was not recovered at the other two insectaries (Table 2). Rates of larval parasitism at the Piedmont insectary were lower than in 1996 when an average of 75% of larvae were parasitized at the end of the season (Kidd 1996). Anaphes flavipes was recovered at both Piedmont and Tidewater; it was not recovered at the Oxford Insectary. The presence of A. flavipes undoubtedly reduced the number of larvae available for late T. julis. On 12 May, approximately 35% of the eggs were parasitized, and the next week, over 45% of the eggs had been attacked. It is notable that A. flavipes was found only in eggs collected in the oat plots at Plymouth. No egg or larval parasitoids were redistributed from the insectary in 1997, but we should see a continuing population at the Piedmont site in 1998.
Acknowledgements
Numerous individuals contributed to this project, and the list includes, but is not limited to John VanDuyn, Stephen Bambara, NCSU, Raymond Coltrain, Ray Horton, Bill Clements, Harold Martin, John Smith, Research Stations, Ron Day, grower, and Robin Goodson, NCDA.
Literature Cited
Haynes, D.L. and S.H. Gage. 1981. The cereal leaf beetle in North America. Ann. Rev. Entomol. 26:259-287.
Kidd, K.A. 1996. Cereal leaf beetle biological control in North Carolina, NCDA BioControl Laboratory Report of Activities. pp. 11-16.
Kidd, K.A. and M.D. Bryan. 1993. Cereal leaf beetle parasitoid insectary program. NCDA BioControl Laboratory Report of Activities. pp. 11-19.
Table 1. Cereal Leaf Beetle Populations, 1997
Piedmont Research Station, Salisbury
| Wheat | Wheat | Oats(1) | Oats(1) | Oats(2) | Oats(2) | |
|---|---|---|---|---|---|---|
| Date | Eggs* | Larvae* | Eggs* | Larvae* | Eggs* | Larvae* |
| 1 Apr | 7.8(7.3) | 2.2(1.6) | 23.3(0.0) | 1.5(0.7) | 15.8(8.3) | 0.3(0.0) |
| 8 Apr | 23.9(3.0) | 15.7(8.0) | 87.8(36.1) | 3.0(0.5) | 65.7(16.5) | 1.5(1.2) |
| 15 Apr | 14.7(6.6) | 7.4(2.3) | 83.5(2.1) | 6.7(1.4) | 41.0(13.2) | 3.3(0.0) |
| 2 May | 0.9(9.2) | 15.5( 15.8) | 6.0(1.0) | 33.0(6.1) | 21.0(10.3) | 18.9(10.1) |
| 6 May | 0.2(0.2) | 20.7( 17.5) | 2.2(0.2) | 20.7(17.5) | 19.2(7.3) | 12.9(5.4) |
| 12 May | 1.7(1.9) | 17.7( 12.7) | 7.7(5.6) | 24.5(0.3) | 24.5(6.8) | 17.8(16.3) |
| 19 May | 0.7(0.9) | 10.4( 2.3) | 3.2(3.1) | 13.8(1.1) | 8.2(4.3) | 11.7(1.9) |
| 28 May | 0.0(-) | 0.9( 1.2) | 0.9(0.2) | 1.8(0.7) | 0.5(0.7) | 3.7(2.3) |
Tidewater Research Station, Plymouth
| Wheat | Wheat | Oats | Oats | |
|---|---|---|---|---|
| Date | Eggs* | Larvae* | Eggs* | Larvae* |
| 2 Apr | 3.5(2.0) | 0.4( 0.6) | 6.5(8.1) | 0.3(1.1) |
| 9 Apr | 3.4(3.3) | 6.0(3.2) | 4.5(1.1) | 8.5(1.7) |
| 16 Apr | 2.5(2.1) | 6.4(5.2) | 3.2(0.7) | 8.0(3.8) |
| 25 Apr | 1.0(0.0) | 3.5(1.1) | 1.4(0.5) | 8.7(1.4) |
| 30 Apr | 3.3(0.0) | 5.5(5.0) | 3.7(0.5) | 14.5(9.7) |
| 5 May | 2.2(1.6) | 1.8(2.6) | 0.3(0.5) | 1.2(0.7) |
| 14 May | 1.5(9.7) | 0.7(0.5) | 0.5(0.7) | 1.8(0.7) |
Oxford Research Station
| Wheat | Wheat | Oats | Oats | |
|---|---|---|---|---|
| Date | Eggs* | Larvae* | Eggs* | Larvae* |
| 21 Mar | 1.3(0.9) | 0.0(-) | (-)** | (-) |
| 3 Apr | 2.2(1.3) | 0.3(0.5) | (-) | (-) |
| 21 Apr | 1.0(0.4) | 1.8(2.1) | 0.0(-) | 0.0(-) |
| 28 Apr | 1.5(0.7) | 1.7(1.9) | 0.0(-) | 0.0(-) |
| 2 June | 0.0(-) | 0.0(-) | 1.4(0.5) | 0.3(0.0) |
*Mean# eggs or larvae/square foot.
** Oats had not emerged.
Table 2. Cereal Leaf Beetle Parasitism, 1997
Piedmont Research Station, Salisbury
| Wheat | Wheat | Oats(1) | Oats(1) | Oats(2) | Oats(2) | |
|---|---|---|---|---|---|---|
| Date | Eggs* | Larvae* | Eggs* | Larvae* | Eggs* | Larvae* |
| 8 Apr | 0.7(0.7)% | 3.85(3.85)% | 0.0% | - | 0.0% | - |
| 15 Apr | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| 2 May | - | 1.8(1.8) | 6.3(3.4) | 4.8(1.0) | 2.1(2.1) | 0.0 |
| 6 May | - | 0.0 | 24.2(14.2) | 3.1(1.2) | 12.4(2.2) | 1.0(1.0) |
| 12 May | - | 1.6(0.5) | 30.0(30.0) | 1.5(1.5) | 39.4(10.7) | 0.5(0.5) |
| 19 May | - | 0.0 | 45.5 | 0.0 | 45.9(4.1) | 0.6(0.6) |
| 28 May | - | 0.0 | - | 11.7(1.3) | - | 24.2(2.2) |
Tidewater Research Station, Plymouth
| Wheat | Wheat | Oats | Oats | |
|---|---|---|---|---|
| Date | Eggs* | Larvae* | Eggs* | Larvae* |
| 9 Apr | 0.0 | 0.0 | 9.4(9.4) | 0.0 |
| 16 Apr | 0.0 | 0.0 | 10.5(4.9) | 0.0 |
| 25 Apr | 0.0 | 0.0 | 25.0(25.0) | 0.0 |
| 30 Apr | 0.0 | 0.0 | 16.7(16.7) | 0.0 |
| 5 May | 0.0 | 0.0 | 0.0 | 0.0 |
| 14 May | 0.0 | 0.0 | 0.0 | 0.0 |
*Eggs were parasitized by Anaphes flavipes. Larvae were parasitized by Tetrastichus julis.
Biological Control of the Cereal Leaf Beetle in North Carolina
Since the cereal leaf beetle, Oulema melanopus (L), was identified in Michigan in 1962, it has been the subject of numerous studies and several dissertations and theses. In 1981, Haynes and Gage published a review of the insect's biology, spread, and the control efforts directed against it in North America. Wellso and Hoxie reviewed the biology of Oulema spp. (1988), including information about O. melanopus, O. gallaeciana (Heyden) (= O. lichenis Weise) a species that may occur with O. melanopus, and the rice leaf beetle O. oryzae (Kuwayama). Additional species, O. duftschmidi (Redtb.) and O. lichenis Voet are also reported to be widely distributed in Europe (Berti 1989, Hansen 1994, Stilmant 1995). In an effort to understand all aspects of the cereal leaf beetle population dynamics, systems science and mathematical modeling have been used to analyze the cereal leaf beetle ecosystem and develop pest management plans (Barr et al. 1973, Haynes et al. 1974, Yun Lee et al. 1976, Haynes and Gage 1981). Native to Europe, O. melanopus is one of several species of Oulema which feed on grains and other grasses in the Palearctic region. Feeding occurs on leaves, between the veins; adult feeding results in elongate slits, but larvae leave the lower epidermis intact (Wellso and Hoxie 1988). Such feeding is typical of criocerine chrysomelids feeding on monocots (Jolivet 1988). In Poland, the spring cereal crops, oats, barley, wheat, and tritcale, are most susceptible to feeding by leaf beetles, but winter wheat, triticale and barley are also susceptible (Bubniewicz et al. 1989). In the earliest study of CLB in Great Britain, Hodson (1929) reported that preferred host plants are barley, oats and wheat, in that order. Knechtel and Manolache (1936) reported that although oats and barley are the preferred hosts, other cereals, corn and grasses are attacked in Rumania. Although Oulema melanopus was described by Linnaeus in 1758, and it is known from earlier European literature (Kadocsa 1916, Hodson 1929, Knechtel and Manolache 1936, Venturi 1942), few studies of its biology are found in the literature prior to 1962 when Oulema melanopus was discovered in North America.
The cereal leaf beetle (CLB) was the target of a large scale classical biological control program in North America during the 1960s and 1970s, and one egg parasitoid, Anaphes flavipes (Foerster) (Hymenoptera: Mymaridae), and four larval parasitoids, Tetrastichus julis (Walker) (Hymenoptera: Eulophidae), Lemophagus curtus Townes (Hymenoptera: Ichneumonidae), Diaparsis carinifer (Thomson) and Diaparsis temporalis Horstmann (Hymenoptera: Ichneumonidae), were released and became established in the north central states of the United States and in Canada (Dysart et al. 1973, Ellis et al. 1978, Horstmann 1979, Maltby et al. 1971, Miller 1977, Stehr 1970, Stehr and Haynes 1972, Stehr et al. 1974). The cereal leaf beetle appears to be under control in that region of North America, however there are occasional outbreaks (M. Bryan, pers. comm., Ellis et al. 1988).
Beginning with field surveys in 1963, parasitoids were collected throughout Europe and introductions to the United States were started the following year (Dysart et al. 1973). Larval parasitoids were released as early as 1964, when adult Diaparsis carinifer and Tetrastichus julis were introduced in Indiana by Purdue University, and subsequent releases followed in Michigan, Indiana, New York, Ohio and West Virginia (Dysart et al. 1973). Anaphes flavipes, although not the first parasitoid of CLB to be released in North America, was the first to became established in Michigan and Indiana; it was recovered in 1968, within two years of its release in 1966 (Maltby et al. 1971). Haynes and Gage (1981) reported that a unique combination of eradication and biological control was attempted: A. flavipes was released along the perimeters of high density infestations to slow the spread of CLB, and the central population was sprayed to eradicate the beetles. Tetrastichus julis, a gregarious bivoltine species, was the first larval parasitoid to become established; evidence of this was found in 1969 at the Kellogg Biological Station of Michigan State University near Gull Lake (Stehr 1970). By then, an increase in T. julis was observed with some populations of CLB exhibiting 100% parasitism.
The distribution of T. julis started in 1971 and continued through 1974; this resulted in the widespread establishment of the parasitoid throughout the lower peninsula of Michigan (Logan et al. 1976). Subcolonization of larval parasitoids was accomplished with the use of insectaries or nursery sites in counties throughout the state. Cooperative extension agents selected sites which would not be disturbed before midseason of the following year, then collected parasitized CLB larvae from the Kellogg station and released them at the nurseries. A recovery program was conducted from 1972-1975 using standardized methods for all counties. These surveys showed that T. julis not only became established but had dispersed to other areas.
The first large release of T. julis in Canada was made in 1974, in the south central region of Ontario (Harcourt et al. 1977), but surveys in 1975 showed high rates of parasitism, indicating that T. julis already had dispersed from Michigan and other states. The average rate of parasitism found was 84%, and in some locations it approached 100%. The practice of planting spring grain crops with a companion crop of legumes, and the elimination of tillage for a year undoubtedly aided the establishment of T. julis. A subsequent survey in 1977 showed the parasitioid persisted, with an average parasitism rate of 70%, and the CLB remained below economic levels (Ellis et al. 1978). Collections north of Lake Huron, where grain fields are more scattered and CLB populations were low, showed a mean parasitism of 65%.
Diaparsis carinifer was reported to be established in the US in 1970, at the Kellogg Biological Station in Michigan (Stehr and Haynes 1972). The authors described variation in colors of D. carinifer related to collection location in Europe, and later work showed there was another species, Diaparsis temporalis, was present in some locations in Europe and it was this species which had become established in North America (Miller 1977, Horstmann 1979).
Stehr and Haynes (1972) provided a description of the conditions for the release and establishment of larval parasitoids and for subcolonization of the parasitoids in other locations. They set as the primary conditions that there be no possibility the field would be sprayed, cereal leaf beetle larvae should be abundant (about 10/ft2 in oats), and the soil should not be disturbed until after emergence of the parasitoids the following spring. Additionally, at the insectary site, oats were planted at 2 to 4 week intervals to provide succulent growth for oviposition over a long period. Subcolonization was accomplished by hand-cutting grain after larvae had been parasitized and transporting the cut stems to the release field. Larvae then finished feeding on grain or grasses in the field border and pupated in the soil. It was felt that D. carinifer (temporalis?) was more active than T. julis, and would disperse from release sites more readily.
Lemophagus curtus was the last European larval parasitoid to become established in North America (Stehr et al. 1974). Little has been written about its population dynamics in the New World, perhaps because it was the last to become established, and studies of cereal leaf beetle and its parasitoids had concluded. During European collections, L. curtus was found in 11 European countries from Sweden to Italy and Yugoslavia, but never south of the Pyrenees in western Europe (Dysart et al. 1973). It was rarely the dominant species, and most often occurred at high host densities. This species is multivoltine with a facultative diapause (Dysart et al., 1973, Stehr et al. 1974). Those individuals which emerged in the summer did so when few CLB larvae were present, and Stehr et al. (1974) predicted that unless the parasitoid had exceptional searching abilities or an alternate host, summer emergence would be selected against. Additional larval parasitoids were collected in Europe in low numbers, but were not released in North America (Dysart et al. 1973).
Haynes (1973) discussed the species interaction and population management potential of the parasitoids which had become established in Michigan and surrounding states. Anaphes flavipes has excellent powers of dispersal and high reproductive potential, but because it is poorly synchronized with its host, and Haynes speculated that this species would have little direct influence on CLB. Because it is most numerous late in the season, Anaphes competes with T. julis for late CLB. Haynes predicted that with 2 generations per year, high reproductive potential, poor powers of dispersal, and better synchronization with the host, T. julis would play a major role in managing CLB. The author noted that a parasite with poor powers of dispersal can be protected, moved, managed and provisioned to overcome some inefficiency. Over 80% of the host population is present when either the first or second generation of T. julis. The impact of the newly established Diaparsis carinifer was uncertain. It appeared to be poorly synchronized with its host in Michigan, appearing late in the CLB life cycle with a low reproductive rate and intermediate powers of dispersal. In contrast, Miller (1977) showed that D. temporalis is well synchronized with the host. The difference may be attributed to the confusion of the two species; they occur together in some European locations, and were probably both released. It would appear, however, that only D. temporalis became established (Miller 1977). The specimens that were recovered in North America had dark abdomens, a characteristic of D. temporalis (Miller 1977).
As the cereal leaf beetle spread south and east from its original introduction in Michigan, surveys were conducted jointly by the USDA and NCDA in NC, and the first collections of CLB in the state occurred in 1977, in 19 counties, primarily along the Virginia border. The early cereal leaf beetle program in NC was aggressive, and its objectives were to map the spread of the pest, monitor population densities, locate potential parasitoid release sites, and to collect information on the life history of CLB in NC. Surveys continued in 40 counties in 1978, and when fields were found with adequate CLB egg densities, Anaphes flavipes, the egg parasitoid, was released in Stokes and Person Counties, both on the Virginia border. Surveys were conducted annually, and in 1980 a strategy was devised to use alternating survey methods. In 1980 and even years following, the objective of the surveys was to monitor changes in population density in infested areas and to select areas with adequate CLB egg and larva densities for parasitoid release. In odd years, the objective of survey activity was to monitor spread of the pest to new counties.
Additional A. flavipes (2 counties) were released in 1979 along with T. julis (10 counties) and D. temporalis (11 counties). A. flavipes was released annually in North Carolina from 1978 to 1981; approximately 66,000 were released in 9 counties, mostly in the central piedmont region. The release material was collected from various locations in the United States and reared at the Niles Biological Control Lab. This parasitoid species has become established in NC, and has apparently dispersed from release sites. It has been collected in at least 4 counties where it was not released (NCDA records).
The first recoveries of larval parasitoids (T. julis) occurred in 1979 in Stokes, Rockingham, and Wilkes Counties. Releases continued, and by 1982, all four species, A. flavipes, T. julis, D. temporalis, and L. curtus had been recovered in NC.
By the end of the CLB season in 1982, large numbers of parasitoids had been released in Northern Piedmont counties. Gladstone (1985a) reported that between 1978 and 1982, 66,860 Anaphes flavipes, 721 Lemophagus curtus, 2469 Tetrastichus julis , and 2473 Diaparsis temporalis had been released. In addition to survey and release work, an insectary was established at the Oxford Tobacco Research Station in 1983. The insectary was designed according to USDA guidelines and consisted of winter wheat followed by two plantings of spring oats. Larvae parasitized with T. julis were obtained from the Virginia Department of Agriculture and Commerce for release in the insectary in 1983 and 1984, and some parasitized by L. curtus were collected in Rockbridge Co., VA, and released in 1984 (Gladstone 1985a). The population density of CLB at the Oxford insectary was low, but considered typical of populations in that region of the state. The low density was attributed to parasitism by A. flavipes (18-20% in mid-May) and predation by coccinellids on eggs and small larvae (Gladstone 1985b). Parasitized larvae for release in Rowan and Davie Counties were obtained from Virginia.The Oxford insectary was discontinued in 1985 due to low CLB populations.
Cereal leaf beetle had spread through most of the grain growing regions of the state by 1984, but densities in fields statewide remained below the threshold of 40 larvae per square foot (Gladstone 1985a). The maximum density recorded that year was 5.3 larvae/sq ft. in an oat field in Guilford County. Highest populations were found in the western piedmont counties of Forsyth, Rockingham, Guilford and Alamance. The larval parasitoid Tetrastichus julis had become established in the Piedmont; it was found in 46% of the fields surveyed (8 counties), the highest occurrence to date. It should be noted that T. julis was not found in four counties where it had previously been collected.
Cereal leaf beetle continued to spread in the state, and T. julis appeared to spread along with it. Two new counties were found positive for CLB in 1986, Hoke and Lincoln, and in 1987, a collection in Onslow County brought the total infested counties to 80, representing most of the small grain producing counties in the state (Godfrey 1986, Godfrey and Keeley 1987, Watson 1987). The highest populations were found in the northern and central piedmont region. Tetrastichus julis was collected from 19.3% of fields sampled in 1986, and it was recorded from 5 new counties that year; no parasitoids had been released in any of these counties (Godfrey 1986).
A large insectary was initiated at the Piedmont Research Station in 1987, as that region of the state remained the most heavily infested with cereal leaf beetle (Godfrey 1986). Parasitized larvae were collected in Virginia for introduction to the Piedmont insectary; 1800 and 44,000 parasitized larvae were introduced in 1988 and 1989, respectively. Larvae from the insectary were dissected on 31 May 1989, and 100% were determined to be parasitized. Subsequently, collections were made from the insectary, and parasitized larvae were distributed to 14 growers in 3 counties (Keeley 1989). Collections of larvae continued through 1992, but numbers of CLB were declining in the insectary, despite annual introductions of adult CLB. Another insectary was started at a new site on the station, but large numbers of parasitoids were not available for "seeding".
USDA-APHIS/PPQ, through the Niles Biological Control Lab, renewed its involvement with cereal leaf beetle biological control in late 1992. Work at the federal level had concluded in 1978, but the continued spread of CLB throughout the south and to the western states of Montana and Utah prompted additional work on the pest. Parasitized eggs and larvae were collected in Europe, and A. flavipes was collected from several locations in the US for rearing in the lab at Niles. Insectaries to rear larval parasitoids were established in North Carolina, as well as in Utah and Montana. In North Carolina, the existing insectaries at the Piedmont Research Station near Salisbury and the Tidewater Research Station near Plymouth in the coastal plain were utilized for this cooperative work. The Tidewater insectary was in its beginning phase and contained no larval parasitoids, but the Piedmont station had an established population of T .julis.
Cereal leaf beetle and its parasitoids were monitored in the insectaries using standardized methodology. The Piedmont insectary consists of two plots, divided into subplots of fall wheat and three or more sequential plantings of spring oats. The Tidewater insectary consists of four plots, with two planted and two fallow. Plots are divided into subplots of fall wheat and spring oats (wheat was used 1993-1996). The presence of adult CLB in the wheat subplots was assessed with a sweepnet early in the spring, at 5 to 10 day intervals. After sweeping, a visual survey of at least 5 minutes was performed to detect eggs and larvae. If eggs were found, square foot counts were taken. Eggs and larvae were counted on all plants in 20.5 in. of row, at 3 locations spread across each subplot. Counts were totalled and recorded as number of eggs or larvae/ft2. The protocol from Niles required samples from the spring plantings only, although data were taken in the fall wheat plantings in some years. Samples of eggs and larvae for the determination of parasitism were collected after the first larvae were found. The protocol specified that 100 eggs and larvae be collected in each subplot. If either stage was scarce, we allotted 15 minutes for searching in each subplot per stage.
To determine if eggs or larvae had been parasitized, samples were returned to the lab. Larvae were placed in 20% ETOH and dissected by K.R. Ahlstrom of NCDA or sent to the laboratory at Niles for dissection. Eggs were placed on glass cover slips in a small petri dish lined with filter paper. These were held at room temperature and monitored for emergence of A. flavipes or other egg parasitoids.
Larval parasitoids were introduced into the insectaries in two ways. Cereal leaf beetle larvae parasitized with three species of larval parasitoids were shipped from Michigan to NC in 1994 for release at the Tidewater insectary. In 1995, adult Diaparsis sp. and T. julis were released in this insectary, but to date, none have been recovered. Adults of Diaparsis sp. and T. julis were released at the Piedmont insectary in 1996 to supplement the existing T. julis population. In addition to the larval parasitoids, approximately 17,000 A. flavipes were released in 5 counties in 1995. The insects had been collected in France, Greece and the US and reared at the Niles laboratory (NCDA lab records).
Work is continuing on this project. We currently have insectaries at Oxford, Tidewater and Piedmont Research Stations, and we are working with growers to monitor the parasitoids at release sites. This control method is best suited for no-till crops; as this cultural practice gains acceptance, we may see more success in establishing the larval parasitoids.
References
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Ellis, C.R. and B. Kormos and J.C. Guppy. 1988. Absence of parasitism in an outbreak of the cereal leaf beetle, Oulema melanopus (Coleoptera: Chrysomelidae), in the central tobacco growing area of Ontario. Proceedings Entomol. Soc. of Ontario. 119:43-46.
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A foreign exploration trip was made 13-30 May with the objective of collecting larval parasitoids of Oulema melanopus, the cereal leaf beetle. Using established methods, I collected larvae during the period of 15-28 May, and allowed them to pupate in the laboratory (Gruber, F., E. Rivet, and C. Prieto. 1972. A technique for obtaining cells of a soil-pupating insect, Oulema melanopus. J. Econ. Entomol. 65:904-906).Collections were initiated on 14 May, by visiting fields near the European Biological Control Laboratory (EBCL) near Montferrier, France. The area had been experiencing a drought, grain crops were small, and CLB populations low. The collection strategy which was recommended by personnel of the EBCL was to examine fields, and collect as many larvae as possible. On 20 May, large collections were not attempted because it was raining; instead, fields were screened, and small samples of 25 larvae were collected in fields with a population of CLB. Larvae were dissected in the laboratory, and ichneumonid parasitoids were found. Results: 17.8% parasitized larvae in one sample, 20.8% in the other. During the next 2 days, I concentrated on these and nearby fields for collections. This latter technique seems more suitable for future collections: make a large circuit to find candidate fields, sample, dissect, then collect as many as possible from specific fields, instead of merely collecting large numbers of larvae. Approximately 2400 CLB larvae were collected, and I also obtained about 6000 which had been collected by USDA personnel near Thessaloniki, Greece. Both collections were placed upon arrival in the NCDA quarantine facility. Adult CLB and other insects were collected as they emerged, and identified by K.R. Ahlstrom of NCDA. Voucher specimens were placed in the departmental collection. The remaining pupal cells were stored at approximately 2°C in an incubator in the quarantine facility for the fall and winter. In early April, the temperature was raised to 26°C. Parasitoids began emerging within 13 days. Total emergence for the summer (1997) and spring (1998) is reported below.
On 29 May, Alan Kirk, EBCL took me to collect ash whitefly natural enemies at the USDA greenhouse at LaValette, a botanical institute near the Agropolis. Encarsia inaron and Clithostetus (Coccinellidae) were present on leaves. I removed as many insects that were not AWF or Encarsia as possible in the lab. The remainder were shipped to the NCDA quarantine facility, but due to the unavailability of AWF at the time, the colony did not become established.
Cereal Leaf Beetle Collections, France and Greece, 1997-1998
| France | Greece | |
|---|---|---|
| Pupal cells | 2400 | 6000 |
| Cereal leaf beetle adults | 1111 | 4026 |
| Tetrastichus sp (1997 & 98) | 20* | 5* |
| Lemophagus curtus (1997) | 1 | 5 |
| Diaparsis temporalis (1998) | 198* | 228* |
*An additional 16 Tetrastichus sp. and 62 Diaparsis temporalis emerged from both boxes (1998). Other insects: 245 dipterans, 234 in Fam. Anthomyiidae, 10 hymenopterans in 5 families.
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Ash Whitefly Biological Control in North Carolina
G.D. Hackney, K.A. Kidd, R.C. McDonald, and N.S. Robbins
G.D. Hackney, K.A. Kidd, R.C. McDonald, and N.S. Robbins
In the fall of 1993, the ash whitefly, Siphoninus phillyreae (Haliday) (AWF), was found to be infesting Bradford pear trees in downtown Raleigh (McDonald et al. 1995). From data collected in California, this species of whitefly is known to be a potential threat to economically important trees including ash, apple, pear, and Citrus species (Bellows et al. 1990). In 1994, Encarsia inaron (Walker), a wasp which parasitizes second through fourth instar larvae of the ash whitefly (Gould et al.1992) was released at selected sites in downtown Raleigh where infestations of S. phillyreae were present. This parasitoid was very effective at reducing the density of S. phillyreae in California (Bellows et al. 1992).
In 1995 and 1996, studies of the S. phillyreae and E. inaron populations were undertaken to determine the effectiveness of E. inaron at controlling S. phillyreae in North Carolina (McDonald et al. 1995 and 1996). Two sites where E. inaron had been released and one control site where they had not been released were chosen for the study. The two release sites were both at the intersection of Jones and Dawson Streets and the control site was on Capitol Boulevard in northern Raleigh. Two thousand wasps had been released at each of the two release sites (McDonald et al. 1995).
In 1995, Siphoninus phillyreae life stages suitable for parasitization were present by 8 August at the release sites. Evidence of parasitization was observed on leaves collected on 24 August. After the discovery of parasitization, the densities (based on colony area) of S. phillyreae eggs, adults, and fourth instar larvae decreased until leaf drop. The rate of parasitization based on parasitized fourth instar larvae reached 82.5% at site 2. Evidence of parasitization was not found at the control site. E. inaron was also found at other sites in downtown Raleigh, including sites where they had not been released. In 1996, individuals were available for parasitization by mid July; however, evidence of parasitzation was not noted until late October. Similar research was undertaken in 1997. Also, in 1997, a total of 4,665 adult E. inaron were released in Wake County.
Materials and Methods
Two new sites were chosen for study in 1997. Site 3 on the corner of McDowell and Martin Streets was chosen to replace site 1 as a release site, and control site 2 on Falls of the Neuse Road was added. Two trees from each site were chosen for sampling. From 17 June until 12 November leaves were collected once every three weeks. Each sample consisted of approximately twenty-five leaves chosen arbitrarily from each tree. The numbers of adult AWF and E. inaron were counted in the field and the leaves from each tree were placed in a separate container and kept in a freezer at the laboratory.
In the laboratory, twenty-five leaves from each tree (fifty leaves per site) were examined for the presence of AWF immatures. Each leaf possessing immatures was placed on a white background, and a glass plate overlaid with a grid was used to determine the boundaries of each colony. The plate was laid on top of the leaf with the grid on the side of the plate nearest the leaf. Small pieces of Velcro® were placed at the corners of this side of the plate to prevent contact with the leaf and damage to the colony. S. phillyreae eggs, early instar nymphs (instars 1-3), and late instar nymphs (fourth instar) were counted with the aid of a binocular dissecting microscope as were E. inaron pupae and exuviae from which either E. inaron or S. phillyreae had emerged. After observation of a leaf sample had begun, the leaves were stored in a refrigerator until observation of that sample was complete.
A Li-Cor Li 3000 leaf area meter was used to determine the areas of one hundred Bradford pear leaves. The areas of these leaves along with their lengths and widths were subjected to correlation analysis in order to derive an equation by which leaf area could be estimated. Density of organisms was based on leaf area.
Results and Discussion
S. phillyreae density was greatest at site 3 (Figure 1.); however, the parasitization rate was much less than at site 2 reaching only0.3%. This was perhaps due to the fact that only one hundred thirty-seven E. inaron had been released at this site (McDonald et al. 1995) which included a larger number of trees than did site 2. Evidence of parasitization was first found at site 2 on a leaf collected on 30 September. A small number of parasitized fourth instar nymphs were found at both release sites as well as at control site 2. The maximum recorded parasitization rate based on parasitized fourth instar nymphs was 6.4% at site 2. The wasps were also found at control site 2 where the recorded parasitization rate reached 3.2%. No evidence of E. inaron was found at control site 1. Although evidence of parasitization was discovered approximately one month earlier in 1997 than it had been in 1996, the E. inaron do not seem to have had a great impact on the AWF densities at any site. The highest densities of both early and late instar nymphs were found on leaves collected on 12 November after the end of the growing season (Figure 1.). Winter seems to be a much greater threat than E. inaron to AWF in North Carolina. Numbers of AWF and E. inaron both plunge after leaf drop leaving a few adult AWF to begin colonies on overwintering hosts such as Pyracantha and Photinia as well as fourth instar AWF nymphs and E. inaron pupae in the leaf litter. AWF are capable of producing one small generation during winter and the following spring on Pyracantha (Hackney, unpublished data). In a study done in northern California, some E. inaron collected as pupae about the time of leaf drop survived for over five months; this far exceeded the observed life spans of fourth instar AWF nymphs during the winter (Dreistadt and Flint). It appears that during the growing season the AWF population must build up from a small seed population each year.
No great economic loss has yet occurred in North Carolina due to the presence of AWF; therefore, AWF may not prove to be a major problem. However, possible future projects include releasing E. inaron in a warmer area such as Onslow county on the coast where it may deal more successfully with the winters, releasing a biotype of E. inaron that is native to an area colder than the biotype currently used, and releasing Clitostethus arcuatus, a beetle used to control S. phillyreae in California (Bellows et al. 1992).Acknowledgments
Thanks to USDA-APHIS for financial assistance; K. Ahlstrom for insect identification; R. Goodson for assistance with charts; and J. Thomas for making possible the use of an NCSU phytotron's leaf area meter.
Literature Cited
Bellows, T.S., T.D. Paine, K.Y. Arakawa, C. Meisenbacher, P. Leddy and J. Kabashima. 1990. Biological control sought for ash whitefly. California Ag. 44:4-6.
Bellows, T.S., T.D. Paine, J.R. Gould, L.G. Bezark and J.C. Ball. 1992. Biological control of ash whitefly: a success in progress. California Ag. 46:24-28.
Dreistadt, S.H. and M.L. Flint. 1995. Ash Whitefly (Homoptera: Aleyrodidae) Overwintering and Biological Control by Encarsia inaron in Northern California. Biological Control. 24:459-464.
Gould, J.R., T.S. Bellows, and T.D. Paine. 1992. Evaluation of biological control of Siphoninus phillyreae (Halliday) by the parasitoid Encarsia partenopea (Walker), using life-table analysis. Biological Control 2:257-265.
McDonald, R.C., N.S. Robbins, J.R. Baker, and T.S. Bellows. 1995. Release and colonization of Encarsia inaron (Walker) (Hymenoptera: Aphelinidae) to control ash whitefly, Siphoninus phillyreae (Haliday) (Homoptera: Aleyrodidae), in North Carolina. NCDA Benef. Insect Lab. Ann. Rept. of Activities. pp. 37-45.
McDonald, R.C., G.D. Hackney, N.S. Robbins, and K.A. Kidd 1996. Ash Whitefly Biological Control in North Carolina. NCDA Benef. Insect Lab. Ann. Rept. of Activities. pp. 33-37.
Figure 1. Mean densities of ash whitefly life stages at selected sites, Raleigh, 1997
Return to the Table of Contents
Rearing First Instar Larvae of Japanese Beetle in the Laboratory
The Japanese beetle (Popillia japonica Newman) (Coleoptera: Scarabaeidae) was first discovered in southern New Jersey in 1916. E.L. Dickerson and H.B. Weiss of the New Jersey Department of Agriculture collected about a dozen beetles in a nursery owned by Henry A. Dreer located between Riverton and Moorestown, New Jersey. These beetles were identified as Japanese beetles. They were known to occur only on the main islands of Japan- Honshu, Kyushu, Shikoku, and Hokkaido until the discovery of the beetles in New Jersey.
It is not known specifically how and when the beetle came from Japan to New Jersey. Fleming (1976) suggested it was probably transported in the grub stage in soil about the rhizomes of Japanese iris.
The beetle found a favorable climate in New Jersey. Large areas of permanent turf provided a habitat for the development of the immature stages. The beetles survived because there were 300 species of plants to feed on and no important natural enemies. By 1974, the beetles had occupied much of the United States east of the 85th meridan. The Japanese beetle is a serious pest on orchard crops, certain field crops such as corn, ornamental trees, and shrubs. It can also destroy turf in lawns, golf courses, pastures, and can damage the roots of some cultivated crops. The beetle is not considered to be an economically important pest in Japan because its natural enemies keep it under control (Fleming 1976).
A method for continuous laboratory rearing of grubs is important to provide the numbers of beetles necessary for year-round entomological studies. Ludwig was the first to successfully rear Japanese beetles in the laboratory. After Ludwig's accomplishment in 1928, most other attempts at rearing all life stages of the beetle in the laboratory were not successful until Goonewardene (1985) used different types of food to rear the grubs and the adults. The roots of a clover-grass mixture served as food for larvae and an artificial diet was used for adults. The mortality of the first instar larvae, reared Goonewardene's method, was usually high (80-90%).
The objective of this study was to compare two different rearing methods. One group of eggs remained in the same pan for their entire development. The other group of eggs was removed from the oviposition container and placed in a fresh container. The hypothesis was that if the handling of the eggs and grubs was reduced, the mortality rate for 1st instar grubs would be lower.
Materials and Methods
Adult Japanese beetles were collected from several locations in Raleigh with traps baited with a floral attractant. An equal number of adults were placed in two 50 x 30 x 20 cm plastic containers (containers A & B). The containers were half-filled with a moist soil and peat moss mixture. The adult beetles were fed fresh slices of apple every two days. The eggs in container B were removed from the soil by using a 20 mesh sieve (Goonewardene 1985). Eggs in container A and container B were stored at 28.5°C in an incubator.
The eggs in container A remained in this same container throughout development. The eggs and grubs were watered three times daily, and rye grass was planted after oviposition began. The soil was gently turned over to count the number of eggs and grubs.
The eggs in container B were removed from the soil by sifting, moved to container C, and held under the same conditions as the controls.
Results and Discussion
The mortality rate of the grubs in this experiment was high (75-85%). There was 76.5% mortality in the controls, and 83.3% mortality in the treatment. Even though the control grubs had a slightly higher survival rate, there was no evidence that proves that movement of the eggs increases mortality.
Literature Cited
Fleming, W.E. 1976. The biology of the Japanese beetle. USDA ARS Technical Bulletin No.1545. pp. 1-2, 67.
Goonewardene, H.F. 1985. Handbook of Insect Rearing: Popillia japonica. Vol 1. P. Singh and R.F. Moore, eds. Elsevier Publishing. pp. 269-278.
Table 1.
Mortality of the first instars| Treatment | #eggs | #1st instars | % Mortality |
|---|---|---|---|
| Control | 23 | 4 | 76.5 |
| Eggs transferred | 25 | 3 | 83.3 |
Release and Probable Establishment of Urophora stylata (Diptera: Tephritidae) in North Carolina for Biological Control of Bull Thistle (Cirsium vulgare)
Bull thistle (Cirsium vulgare (Savi) Tenore (Asteraceae)), a plant of Eurasian origin, is a widespread weed on several continents (Forcella and Randall 1994, Holm et al. 1997). In North Carolina, bull thistle is mainly a weed of pasture land, and is common throughout the state, especially in the Piedmont and mountain regions (Radford et al. 1968). C. vulgare is probably the most widespread and numerous non-native weedy thistle in North Carolina, but its abundance and weed severity vary greatly from area to area in the state, and even from field to field.
C. vulgare is typically a biennial, and reproduces solely by means of seed production (Forcella and Randall 1994; Holm et al. 1997; Klinkhamer and De Jong 1988, 1993; Klinkhamer et al. 1988). Livestock are reluctant to consume bull thistle, and large thistle populations can significantly reduce pasture yields. In regions where the plant is a non-native weed, bull thistle spreads primarily through the transport of seeds in contaminated hay, crop seeds, and machinery, or by wind. Seeds can persist in the soil for years before germinating, producing a chronic weed problem in infested areas (Doucet and Cavers 1996, Van Breeman and Van Leeuwen 1983, Williams 1966). Bull thistle can be controlled effectively with the use of chemical herbicides or by mowing (Forcella and Randall 1994), or with good pasture management (e.g., avoidance of overgrazing (Forcella and Wood 1986)). These management techniques, however, are not practiced uniformly in areas of bull thistle infestation, and can sometimes be cost prohibitive. Furthermore, reinfestation of thistle-free land can easily occur by the spread of seed from nearby land where bull thistle is not controlled. Research and implementation of biological control methods for bull thistle management is being conducted by the NCDA&CS to contribute towards effective, permanent, self-sustaining, economical, and environmentally friendly thistle control on public and private lands.
Bull thistle has been a target weed for biological control efforts in several countries, including the United States (Julien 1992). Insect natural enemies employed for biological control of bull thistle include the rosette-feeding weevil Trichosirocalus horridus (Panzer) (Coleoptera: Curculionidae), strains of the flower head-infesting weevil Rhinocyllus conicus (Frölich) (Coleoptera: Curculionidae), and the flower head-infesting fly Urophora stylata (Fabricius) (Diptera: Tephritidae). U. stylata has been released against bull thistle in South Africa (Zimmermann 1991), Canada (Harris and Wilkinson 1984, Redfern and Cameron 1989) and in the United States where it is now established in Washington, Oregon, Colorado, and Maryland (Piper 1985, Rees et al. 1996). In Australia, U. stylata is presently under investigation for use against bull thistle (Aeschlimann et al. 1996).
Urophora stylata is a univoltine fly species native to Europe where its principal host plant is Cirsium vulgare (Redfern 1968, White and Clement 1987, Zwölfer 1972). Prepupal larvae overwinter in hardened galls in senesced C. vulgare flower heads; adults emerge in early summer. Mating occurs, and females deposit small groups of eggs among the bracts of C. vulgare flower head buds. Larvae hatch and burrow down into the developing ovarioles by means of corolla tubes. Each larva feeds within ovariole tissue and adjacent receptacle, producing a hardened and increasingly larger gall. The individual galls increase in size and, by late summer or early fall, coalesce until each flower head contains a single hardened marble-sized to golf ball-sized multi-chambered gall. U. stylata's value as a biocontrol agent against bull thistle is derived from its larval feeding on developing ovarioles and receptacles, and the resultant decrease in thistle seed production. In a Canadian post-release study, Harris and Wilkinson (1984) found that U. stylata can reduce bull thistle seed production by >50% in infested flower heads.
Materials and Methods
Working under permits issued by the NCDA&CS and USDA-APHIS, Urophora stylata-infested bull thistle flower heads were obtained from the Oregon Department of Agriculture. The flower heads contained galls with U. stylata pupae and pre-pupal larvae from the previous year. The plant material had been refrigerated for the winter.
Adult U. stylata were reared in the laboratory for release in North Carolina, rather than risking the release of U. stylata parasitoids or bull thistle seeds in North Carolina by placing plant material from Oregon at field sites in North Carolina. Upon arrival from Oregon, the galled bull thistle flower heads were placed on a shallow layer of clean sand in a plexiglass-topped sleeve cage. The plant material was misted with water 2 or 3 times daily to soften the galls, making adult fly emergence easier. For food, adult flies were provided sugar water soaked into small pieces of sponge.
Adult flies were captured in the sleeve cage using a large aspirator, and placed in large plastic vials provided with loosely crumpled tissue paper for resting sites. The flies were transported to release sites in coolers. Adults were released at three sites (Table 1.) -- two sites in the eastern Piedmont and one site in the western Piedmont. Releases of adults were made on bull thistles with flower heads ranging from the bud stage to full bloom. The plastic vials were opened at the base of a bull thistle plant and gently tapped to encourage the flies to exit. Releases were made in the open without the use of protective cages.
Results and Discussion
Upon their release on bull thistle, most flies flew up into the plant where they were released or flew to other nearby thistles. A number of flies were seen mating, and females were observed probing thistle flower heads with their ovipositors.
In October, after the bull thistles were mature and had senesced, the release sites were revisited to determine if flies had survived, laid eggs, and produced galls on bull thistle plants. Galled flower heads are easily detected by squeezing mature flower heads with a gloved hand. Galls were found at all three release sites (Table 1.), indicating that flies had indeed survived, oviposited, and their resultant larvae had survived at least until the end of the summer. To minimize the effect on subsequent fly populations, destructive sampling for galled heads was kept to a minimum. Several of the galls were returned to the laboratory where dissection revealed the presence of live, pre-pupal U. stylata larvae.
Based on our observations, it appears that U. stylata has so far become established at our release sites. In the summer of 1998, further observations will be made to determine if U. stylata pre-pupal larvae successfully overwintered, emerged as adults, and produced a new generation. Also, we expect to receive additional U. stylata from the Oregon Department of Agriculture for release in North Carolina. When U. stylata populations become well established, we plan to quantify fly population levels and their damage to bull thistle. Hopefully, U. stylata will complement the effects of the rosette weevil Trichosirocalus horridus (Kidd and Nalepa 1997, McDonald et al. 1994, McDonald and Robbins 1995) for biological control of bull thistle in North Carolina.
Acknowledgments
I thank the following for their generous assistance and cooperation during this work: Eric Coombs (Oregon Department of Agriculture, Salem), Matt Taylor (North Carolina Cooperative Extension Service, Lincolnton, NC), and Tom Coley (Rocky Mount, NC).
References
Aeschlimann, J.-P., R. Groves, S. Hasan, M. Jourdan and J. Vitou. 1996. Biological control of other thistles. In Commonwealth Scientific and Industrial Research Organization (CSIRO) Entomology, Report of Research 1993-95, Weed Management. CSIRO, Australia. World Wide Web address: http://www.ento.csiro.au/research/rr93-95/wd-temp.htm#other.
Doucet, C. and P. B. Cavers. 1996. A persistent seed bank of the bull thistle Cirsium vulgare. Canadian J. Botany 74: 1386-1391.
Forcella, F. and J. Randall. 1994. Biology of bull thistle Cirsium vulgare (Savi) Tenore. Reviews of Weed Science 6: 29-50.
Forcella, F. and H. Wood. 1986. Demography and control of Cirsium vulgare (Savi) Ten. in relation to grazing. Weed Research 26: 199-206.
Harris, P. and A. T. S. Wilkinson. 1984. Cirsium vulgare (Savi) Ten., bull thistle (Compositae), pp. 147-153. In Kelleher, J. S. & M. A. Hulme [eds.], Biological control programmes against insects and weeds in Canada 1969-1980. CAB, London.
Holm, L., J. Doll, E. Holm, J. Pancho and J. Herberger. 1997. World weeds: natural histories and distribution. John Wiley and Sons, New York. xv + 1129 pp.
Julien, M. H., ed. 1992. Biological control of weeds: a world catalogue of agents and their target weeds, 3rd ed. CAB International. viii + 186 pp.
Kidd, K. A. and C. A. Nalepa, eds. 1997. Annual Report of Activities, 1996. NCDA Beneficial Insects Laboratory, Raleigh, North Carolina.
Klinkhamer, P. G. L. & T. J. De Jong. 1988. The importance of small-scale disturbance for seedling establishment in Cirsium vulgare and Cynoglossum officinale. J. Ecology 76: 383-392.
Klinkhamer, P. G. L. and T. J. De Jong. 1993. Biological flora of the British Isles. Cirsium vulgare (Savi) Ten. J. Ecology 81: 177-191.
Klinkhamer, P. G. L., T. J. De Jong and E. Van Der Meijden. 1988. Production, dispersal and predation of seeds in the biennial Cirsium vulgare. J. Ecology 76: 403-414.
McDonald, R. C., K. A. Kidd and N. S. Robbins. 1994. Establishment of the rosette weevil, Trichosirocalus horridus (Panzer) (Coleoptera: Curculionidae) in North Carolina. J. Entomol. Science 29: 302-304.
McDonald, R. C. and A. O. Robbins. 1995. Biological control of bull thistle using a beneficial weevil. Guide sheet, NCDA Plant Industry Division, Raleigh.
Piper, G. L. 1985. Biological control of weeds in Washington: status report, pp. 817-826. In Delfosse, E. S. [ed.], Proceedings of the Sixth International Symposium on Biological Control of Weeds, 19-25 August 1984, Vancouver, Canada. Agriculture Canada, Ottawa.
Radford, A. E., H. E. Ahles and C. R. Bell. 1968. Manual of the vascular flora of the Carolinas. University of North Carolina Press, Chapel Hill.
Redfern, M. 1968. The natural history of spear thistle-heads. Field Studies 2: 669-717.
Redfern, M. and R. A. D. Cameron. 1989. Density and survival of introduced populations of Urophora stylata (Diptera: Tephritidae) in Cirsium vulgare (Compositae) in Canada, compared with native populations, pp. 203-210. In Delfosse, E. S. [ed.], Proceedings of the Seventh International Symposium on Biological Control of Weeds, 6-11 March 1988, Rome, Italy. Istituto Sperimentale per la Patologia Vegetale, Italy.
Rees, N., P. Quimby, Jr., G. Piper, E. Coombs, C. Turner, N. Spencer and L. Knutson. 1996. Biological control of weeds in the West. Western Society of Weed Science in cooperation with USDA Agricultural Research Service, Montana Department of Agriculture, and Montana State University, Bozeman.
Van Breeman, A. M. M. and B. H. Van Leeuwen. 1983. The seed bank of three short-lived monocarpic species, Cirsium vulgare (Compositae), Echium vulgare and Cynoglossum officinale (Boraginaceae). Acta Bot. Neerl. 32: 245-246.
White, I. M. and S. L. Clement. 1987. Systematic notes on Urophora (Diptera: Tephritidae) species associated with Centaurea solstitialis (Asteraceae: Cardueae) and other Palaearctic weeds adventive in North America. Proc. Entomol. Soc. Washington 89: 571-580.
Williams, J. T. 1966. Variation in the germination of several Cirsium species. Tropical Ecology 7: 1-7.
Zimmermann, H. G. 1991. Biological control of spear thistle, Cirsium vulgare(Asteraceae), in South Africa. Agriculture, Ecosystems and Environment 37: 199-205.
Zwölfer, H. 1972. Investigations on Urophora stylata Fabr., a possible agent for the biological control of Cirsium vulgare in Canada. Weed projects for Canada. Commonwealth Institute of Biological Control Progress Report 29. 20 pp.
Table 1.
Urophora stylata released in North Carolina, summer 1997.| Release Date | No. Adult Flies Released | Location | Status |
|---|---|---|---|
| 30 June | 150 | Lincoln County, dairy farm | galls found, 14 October 1997 |
| 11 July | 180 | Nash County, beef cattle pasture | galls found, 24 October 1997 |
| 17 July | 190 | Franklin County, abandoned hog farm | galls found, 7 October 1997 |
| Total: | 520 |
Mass Appearance of Lady Beetles (Coleoptera: Coccinellidae)
on North Carolina Beaches1
on North Carolina Beaches1
ABSTRACT: A mass appearance of lady beetles on the North Carolina coast was investigated in May of 1996. Six species of lady beetles were identified, with Hippodamia convergens and Coccinella septempunctata predominating. It is suggested that the insects were first-generation adults dispersing from senescing grain fields.
Several publications document the sudden appearance of hordes of lady beetles (Coccinellidae) on the beaches of oceans and large lakes (Oliver, 1943; Hagen, 1962; Rothschild, 1971;Yan et al., 1983; Majerus and Majerus, 1996). These sporadic mass appearances are not associated with dormancy or aggregation and are usually attributed to the weather. Wind patterns concentrate masses of flying beetles and drop them into bodies of water; large numbers of beetles subsequently wash up on beaches as the result of wind and tides. The number of beetles involved can be staggering. Oliver (1943), for example, described a drift line of dead Coccinella undecimpunctata L. at least 13 miles long with 70,000 beetles per linear foot. In the United States the phenomenon has been reported by Lee (1980) in the Great Lakes of the upper midwest, and by Schaefer et al. (1987) along the coast of Delaware. Hagen (1962) reported that masses of Hippodamia convergens Guerin-Meneville are occasionally deposited in the Pacific Ocean.
We had the opportunity to investigate reports of a large number of coccinellids washed up on a beach in the city of Kitty Hawk (36.07oN, 75.72oW) on one of North Carolina's barrier islands. Local residents reported that the lady beetles arrived in large numbers on 18 May 1996. On 25 May 1996 we collected and identified 919 insects from debris east of the primary dune. Of these, 96% were predaceous coccinellids, 3% were other Coleoptera, and 1% were assorted Hemiptera and Diptera. Seven percent of the insects were alive when collected, and all but the Diptera were identified to species (Table 1.). Six species of lady beetles were collected, with Hippodamia convergens and Coccinella septempunctata L. dominating (55.8% and 41.5% of Coccinellidae collected, respectively).
To determine if this mass appearance was a localized anomaly, one week later (1 June 1996) we visited Wrightsville Beach, NC (34.21oN, 77.80oW), 281 km south of Kitty Hawk.
Seventy-two dead beetles were collected in debris at this location: H. convergens (51.4%), C. septempunctata (44.4%), C. munda (2.8%), and C. maculata lengi (1.4%). The three non-coccinellids collected were identified as Chrysomela scripta (Fabricius). These beetles were all dead and infrequently encountered. We suspect that the insects collected at both Kitty Hawk and Wrightsville Beach were remnants of the same phenomenon, but most of the beetles at the latter location had washed or blown away by the time we visited.
The species collected at Kitty Hawk are a common assemblage of lady beetles in North Carolina and are reported in varying proportions from crops and ornamental plantings (Kidd, 1996; Nault, unpublished data; Nalepa, unpublished data). All are aphidophagous to varying degrees, conforming to the prevailing hypothesis that mass appearances of lady beetles on beaches are related to the nature of their aphid diet (Hodek, 1973; Hodek et al., 1993). Aphids rapidly increase in number under favorable conditions, but this abundance is sporadic and ephemeral in most habitats (Hodek, 1973). Aphidophagous lady beetles, in turn, have evolved two traits that predispose them to tracking prey of this nature. First, they are able to respond to an abundance of prey with spectacular increases in population size (Hagen, 1962; Hodek, 1973; Hodek and Honek, 1996; Majerus and Majerus, 1996). Dickson et al. (1955), for example, estimated that nearly 54,000 adult coccinellids emerged from one acre of alfalfa heavily infested by aphids. Second, aphidophagous lady beetles are more nomadic than species that use other food sources, and may switch among several habitats with suitable prey during one vegetational season. They are especially prone to fly when hungry (Ewert and Chiang, 1966a,b; Hodek et al., 1993; Hodek and Honek, 1996; Majerus and Majerus, 1996).
In explaining the mass shoreline appearances of aphidophagous coccinellids, Hagen (1962) proposed a plausible chain of events subsequently echoed and endorsed by other authors (Hodek, 1973; Hodek and Honek, 1996; Majerus and Majerus, 1996). Favorable environmental conditions, i.e., massive aphid populations and optimal weather, allow for a high fecundity of female coccinellids and a low mortality of larvae and pupae. Juvenile populations build quickly, and when the young adult beetles of this generation emerge, there is stiff competition for remaining prey. Hunger increases their mobility, a hot day may bring them into the air by the millions; their numbers may be further concentrated by thermals and prevailing winds. The beetles are brought back to earth en masse by air currents at the coast and perhaps a reluctance to cross expanses of water. Those that land in water are washed back onto the coast by wave action and tides.
Hodek and Honek (1996) consider the species composition of these mass appearances purely accidental "pseudo-communities" that may not resemble coccinellid communities of any habitat in the vicinity; they cite Klausnitzer's (1989, 1992) work on the German coast of the Baltic Sea. This researcher compared relative abundance of coccinellid species from seashore collections with those present in nearby pine forests and found little correlation. The timing and species composition of the mass appearance of coccinellids on North Carolina beaches in 1996, however, suggests the possibility that these originated in grain fields prevalent in the eastern half of the state. First, nearly 700,000 acres of small grains were harvested in this area of North Carolina during 1995; harvest typically begins in late May and early June (Meadows, 1996). Second, adults of the first generation of coccinellids emerge in late May, at about the same time grain is senescing (Kidd, 1996; Nault, unpublished data). Third, over most of North Carolina prevailing winds near the earth's surface blow from the southwest. The direction may be interrupted and reversed due to offshore storms or diurnal fluctuations (Hardy et al., 1967). Fourth, two of the major species comprising the beach population were also abundant in nearby grain fields. Lady beetles swept from wheat at the Tidewater Research Station near Plymouth in Washington County on 3 May 1996 consisted of 38.3% C. septempunctata, 30.4% H. convergens, and 31.3% C. maculata (n = 240) (Kidd, 1996).
The presence of C. septempunctata and H. convergens at the beach is not difficult to explain. C. septempunctata is primarily an aphid predator (Gordon, 1985) prone to population explosions (Hodek and Honek, 1996; Majerus and Majerus, 1996), is a strong flier (Marriner, 1939), and is the dominant species collected from mass aggregations on coastlines (Rothchild, 1971; Yan et al., 1983; Schaefer et al., 1987). During the breeding period, the most important movements of C. septempunctata in Europe occur after aphids disappear from cereal stands, when the emergence of new adults more or less coincides with a decline in the aphid populations in the fields (Hodek and Honek, 1996). H. convergens represented a higher proportion (55.8%) of our beach collection than has been reported in the past. In the coastal collection described by Schaefer et al. (1987), for example, just 5.3% were identified as H. convergens. This coccinellid is strictly aphidophagous, and can be the most abundant species present in cereals (Gordon, 1985; Hodek and Honek, 1996:Table 5.16). If the lady beetles that appeared on the North Carolina coast in 1996 indeed originated from small grain, then Coleomegilla maculata is conspicuous by its relative absence from the beach. Although its scarcity might be due to variation in demographic parameters (i.e., adults of the first generations of C. septempunctata and H. convergens may have emerged and flown while C. maculata were still pupae), we think a better explanation lies in host range differences among species. While the primary food source of C. septempunctata and H. convergens is aphids, C. maculata is perhaps the most polyphagous lady beetle known, feeding on aphids, other insect prey, insect eggs, fungi, and pollen (Hodek, 1973; Hilbeck and Kennedy, 1996). Up to 50% of the diet of C. maculata can be composed of pollen from various plants (Forbes, 1883). As such, the life history of this species is not strongly tied to aphid demographics (Ewert and Chiang, 1966b), and it is less prone to long distance movements (Hodek and Honek, 1996). After the collapse of aphid populations in small grain, new adults of C. maculata can support themselves on nearby alternative food instead of undertaking a risky dispersal flight in search of aphid prey. Voucher specimens have been deposited in the North Carolina Department of Agriculture Insect Collection, Raleigh.
Acknowledgments
We thank Robin Goodson and George Kennedy for commenting on the manuscript, and alert citizen Jenny Rand for reporting the coastal coccinellid convergence.
Table 1.
. Insect species collected from beach debris at Kitty Hawk, North Carolina, on 25 May 1996 (n= 919 insects; 7 Diptera were not identified).| Family | Species | No. |
|---|---|---|
| Coccinellidae | Hippodamia convergens Guerin-Meneville | 493 |
| Coccinella septempunctata L. | 367 |
|
| Cycloneda munda (Say) | 15 |
|
| Harmonia axyridis (Pallas) | 6 |
|
| Coleomegilla maculata lengi Timberlake | 2 |
|
| Anatis labiculata (Say) | 1 |
|
| Scarabaeidae | Macrodactylus angustatus (Beauvois) | 3 |
| Chrysomelidae | Diabrotica undecimpunctata howardi Barber | 8 |
| Chrysomela (Microdera) scripta (Fabricius) | 7 |
|
| Leptinotarsa decemlineata (Say) | 5 |
|
| Calligrapha (Coreopsomela) californica coreopsivora Brown | 2 |
|
| Saldidae | Saldula major (Provancher) | 1 |
| Pentatomidae | Neottiglossa (Texas) cavifrons Stal | 1 |
| Cydnidae | Sehirus cinctus (Beauvois) | 1 |
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Entomophaga maimaiga Infection in Gypsy Moth Larvae - 1997
Janet L. Shurtleff
Soil infested with E. maimaiga was collected from Rockbridge County, VA in November 1996. The infested soil was distributed in November and December 1996 in 11 gypsy moth infested locations in Dare, Currituck, and Camden counties. Sites were selected for treatment based on having a moderate to high gypsy moth population and being in a location where pesticide applications were not desirable or appropriate to control the pest. Up to 10 trees were treated and burlap-banded at each site. Approximately 2 kg infected soil was placed in the soil around the banded tree. The treated area was watered and the leaf litter was replaced over the treated area to enhance fungal survival.
A total of 819 gypsy moth larvae were collected weekly at each location in three collections in May 1997. Third to 5th instar gypsy moth larvae were collected from the burlap bands on treated trees. Up to 30 larvae were collected at each location on each sampling date. A check area, removed from the treated area, was also sampled at each location. Larvae were reared in the laboratory on artificial diet in 6 oz. plastic cups until they died or emerged as healthy adults. Dead larvae were dissected for the presence of E. maimaiga conidia and azygospores (resting spores), and NPV (nuclear polyhedrosis virus) inclusion bodies.
Most of the larvae died of stress or emerged healthy as adults (86%). However, 14% of the larvae died of either diseases or parasitism by tachinid flies or wasps, summarized below:
A. Disease - 11.2% of total
| Disease | #Larvae | % of Total |
|---|---|---|
| Entomophaga maimaiga | 53 |
6.4 |
| NPV (virus) | 39 |
4.8 |
| Both(E. maimaiga + NPV) | 6 |
0.7 |
B. Parasitism - 2.8% of total
| Species | #Larvae | |
|---|---|---|
| Lespesia aletiae | (Diptera:Tachinidae) | 16 |
| Hyphantrophaga virilis | (Diptera:Tachinidae) | 5 |
| (Cotesia spp. | (Hymenoptera:Braconidae) | 1 |
Larvae infected with E. maimaiga were found at all 11 soil distribution sites. However, the vast majority of infected larvae were collected from the Southern Shores locations:
| Location | # Infected |
|---|---|
| Southern Shores 1 | 21 |
| Southern Shores 2 | 12 |
| Rest Stop | 5 |
| Riveria | 4 |
| Shawboro 2 | 3 |
| Original Old Trap | 2 |
| Bertha | 1 |
| New Old Trap | 1 |
| Shawboro 1 | 1 |
| Shawboro 3 | 1 |
| Southern Shores 3 | 1 |
Infected larvae were collected on all collection dates. Conidia were found primarily on the specimens collected 5/14/97, and resting spores were most common in those collected 5/21 and 5/28/97. No infected larvae were found in untreated areas.
Since nearly twice as many infected larvae were collected 5/28/97 compared to 5/14/97 we are planning to bracket a longer time period for collection in 1998.
Apiary Inspection Program
The year 1997 has been erratic in many ways. The plight of the beekeeper has been recognized by several different non apiary organizations, and assistance to the beekeeping industry has been demonstrated by a number of these groups. In the early months of this year there seemed to be little hope of maintaining our use of the ETO chamber; the EPA had put forth a decision to ban most minor uses of this material. Fortunately, the EPA accepted our economic and safety data and decided that continued use of this procedure was justified. Our appeal to them was bolstered by other beekeeping organizations from several states, the American Beekeeping Federation, the Apiary Inspectors of America, as well as the National Association of State Departments of Agriculture. Thanks to these efforts, and to the guidance of NCDA's Pesticide Division, the assistance of our state OSHA, and Department of Labor boiler safety inspectors, we are now the national model for the use of the ETO chamber in decontaminating beekeeping equipment.
This year we also received some economic assistance from our state legislature .This was achieved through the tireless efforts of the NC State Beekeepers Association. These funds will enable us to take a more proactive course in protecting our bees from future diseases and pests as well as develop better methods to deal with those pests and diseases already within our state borders. As a reflection of this, our field inspectors are already participating in workshops throughout the state. Most of these are done in cooperation with the local county associations and or the NCSU Apiary Extension office . We are seeing record numbers of new and potential beekeepers. We are also in the process of altering our inspection forms and data gathering procedures to make the information gathered more meaningful in evaluating the overall condition of the state's beekeeping industry.
As previously stated this has been an unusual year. Colony conditions were excellent this spring, ready for a fantastic honey flow. Unfortunately the weather didn't cooperate and many bees were left with little to forage and not much else to do but swarm, (and swarm, and swarm). Although the spring and summer flows did not come up to expectations, the fall flow was exceptionally strong. In many cases hives that were on the verge of starvation in August were honey bound by October. This is certainly the more favorable of these two conditions, however it may reveal some negative results this spring. (The early cessation of brood rearing this fall may cause some colonies to be heavily stressed this spring).Time and the timing of the weather will tell. As of December 97, there is little reason not to be optimistic about the future of the beekeeping industry in North Carolina.
The saddest news of the year came with the passing of Jimmy Greene who died on October 21. He had set the tone for the apiary inspection program for the past forty plus years. His presence will be sorely missed while his memory and influence will remain as an inspiration to all of us who had the opportunity to work with him.
For Additional Information Contact:
Plant Protection Section - Kathleen Kidd, Biological Center Administrator
Mailing Address: 1060 Mail Service Center, Raleigh NC 27699-1060
Physical Address: 950 E Chatham St, Cary, NC 27511
Phone: (919) 233-8214 FAX: (919) 233-8394
NCDA Plant Industry Divisions - Plant Protection Section
Plant Pest Administrator : Stephen P. Schmidt
Mailing Address: 1060 Mail Service Center, Raleigh NC 27699-1060
Physical Address: 216 West Jones Street, Raleigh NC 27603
Phone: 919) 733-6930 ext. 231; FAX: (919) 733-1041