Agronomic Services - Nematode Management in Soybeans
To minimize damage, implement the control practice(s) recommended by the note(s) specified on your nematode assay report.
Nema Notes 2
Soybean cyst nematode is present. Soybeans and snap beans are the only host crops for this nematode commonly grown in North Carolina. Crop rotation is useful in managing soybean cyst nematode:
| Year | Rotation |
|---|---|
| 1 | nonhost crop |
| 2 | cyst-resistant soybean variety |
| 3 | nonhost crop |
| 4 | cyst-susceptible soybean variety |
Growing small grains in winter is not equivalent to growing a nonhost crop for an entire year. If soybean cyst nematode populations are very high, grow nonhost crops for at least two consecutive years. Three years is even better. If high populations of cyst nematodes occur after a year of cyst-resistant soybeans, see Note 2-3.
This sample indicates an infestation of soybean cyst nematode. Take another sample from this field before planting soybeans or snap beans.
This sample indicates a high population of soybean cyst nematodes on or following a cyst-resistant variety. Currently available varieties with the same cyst-nematode resistance will probably not be effective against this population. Choose a variety with different resistance. See comments on managing nematodes on soybeans with resistant varieties in Note 2-6.
If possible, follow soybeans with nonhost crops for two consecutive years. After nonhost rotation, you can grow a susceptible soybean variety with lower risk of damage. If only a one-year rotation is possible, then consider the rotation schedule below. Planting a variety in maturity group V after June 15th may give acceptable yields.
| Year | Rotation |
|---|---|
| 1 | nonhost crop |
| 2 | soybean variety with a different resistance |
| 3 | nonhost crop |
| 4 | cyst-susceptible soybean variety |
This sample indicates the presence of root-knot nematodes. Plant a resistant soybean variety this year to help manage the nematode and prevent it from becoming a problem for future crops.
The information sheet did not indicate the variety of the previous soybean crop. If a cyst-resistant variety was used, it was not effective. Follow the suggestions in Note 2-3.
The information sheet did not provide complete cropping history. The sample indicates the presence of soybean cyst nematodes. If it has been two or more years since soybeans or snap beans were grown in the field, then these nematodes are not likely to damage next year's soybean crop. However, if these crops have been grown within the last two years, damage may be severe.
Managing the Columbia Lance Nematode
Soil type affects damage by the Columbia lance nematode. Damage is most severe on sandy soils. The information in TABLE 1 can be used to predict the likelihood of damage by lance nematodes.
Some soybean varieties are tolerant to the Columbia lance nematode. A tolerant variety will yield more than a susceptible one at low to moderate nematode populations but can be severely damaged if nematode populations are high. Tolerant varieties, however, neither prevent nor limit nematode reproduction and development.
Potential for Columbia lance nematode damage based on nematode population level and soil type.
| Nematodes per 500 cc soil | Potential damage in sandy soil | Potential damage in clay, mineral, or organic soil |
|---|---|---|
| 10-50 | low | low |
| 50-100 | moderate | low |
| 100-200 | high | low |
| 200-400 | high | moderate |
| 400+ | high | high |
Managing Nematodes on Soybeans with Resistant Varieties
Cyst-nematode-resistant soybean varieties are not all the same. There are at least nine races of cyst nematodes (identified by numbers), and varietal resistance is specific. For example, a variety listed as resistant to races 3 and 14 is only resistant to those races. The grower should take care to select the correct variety. If soybeans resistant to races 3 and 14 have not been effective in reducing cyst populations (as determined by assays before and after planting), select a variety with resistance to other races (for example, 2, 5 or 9).
Lists of soybean varieties with resistance to the various races of soybean cyst and root-knot nematodes are available from many sources, including seed companies and NC State Extension. Varietal performance is provided by the NCSU Official Variety Testing Program where you can search for resistant varieties using the Variety Selection Tool.
Information on soybean resistance to other nematodes tends to be less accessible. Resistant varieties grow well in infested fields and actually suppress existing nematode populations. Moderately resistant varieties may permit some nematode reproduction. As mentioned in the previous section, tolerant varieties will grow in infested fields but do not suppress nematode populations and still exhibit some yield loss.