Each year, potential problem areas are identified using data from NCDA&CS gypsy moth traps. During the fall, each infestation is examined in hopes of finding the exact population location. If it is found and it is small (several acres or less in size), it may be treated from the ground. If the infestation is not found or if it is too large to treat from the ground, it is treated aerially. Depending on estimated gypsy moth population density, landcover/landuse type, and funding, these areas are treated using one of the methods detailed below.
There are many insecticides labeled for use against gypsy moth; however, NCDA&CS only uses the environmentally friendly insecticides detailed below, as others are more toxic to nontarget organisms or harmful to the environment. As new products become available, NCDA&CS, in cooperation with the US Forest Service and the Gypsy Moth Slow the Spread Foundation, will evaluate their potential for use in the NCDA&CS Gypsy Moth Program.
Btk (Bacillus thuringiensis var. kurstaki, trade name Foray® 76B)
Btk is a bacterium commonly found in forest soils worldwide. It has become one of the most valuable biological pest management tools for a variety of agricultural, forestry, and urban pests. While it is highly toxic to target pests, it is very safe in regard to humans and animals. For example, different formulations of the same biopesticide are labeled to be applied to organic grains such as shelled corn and soybeans during storage and/or to organic bagged grains (popcorn) to prevent Indian meal moth. Here is a link to Organic Gardening which refers to the use of Btk in the home vegetable garden to control cabbage loopers.
Btk must be consumed by caterpillars to be effective. Once ingested, the alkaline gut of the caterpillar activates the bacteria. Note that, as humans and animals have acidic rather than alkaline digestive tracts, the bacteria is harmless to us. Caterpillar feeding ceases; within several days, the caterpillar has died. Btk is unique in being highly effective while also being environmentally friendly. Btk is effective at all gypsy moth population densities.
Btk is usually applied by airplane or helicopter, but may be applied by a mist blower on the ground. It is usually applied twice: once when approximately 70 percent of the larvae have reached the second instar (mid to late April), and a second time five to seven days later. While harmless, Btk will smell bad during the several hours it takes to dry.
Today’s highly advanced aerial application technology has enabled precision, ultra-low volume treatments of one-third of a gallon to the acre per application, or 0.001 fluid ounces per square feet. This means that one cup of Btk will cover approximately 8,167 square feet. Btk is highly sensitive to solar radiation; thus, care must be taken to apply the product at exactly the correct time.
Pheromone flakes (trade name Disrupt® II)
Several decades ago, scientists isolated and discovered how to manufacture the chemical compound that serves as the female gypsy moth sex pheromone. Specific to gypsy moths, this compound was first used to bait the traps used to catch male gypsy moths and estimate gypsy moth population densities. Scientists discovered another use for this compound: if enough pheromone is applied at the right time, it saturates the area with pheromone so that males would not be able to follow the natural pheromone scent trails released by female gypsy moths. This decreases mating success and suppresses the gypsy moth population.
Now, miniature plastic chips are infused with the pheromone, combined with an adhesive, and applied once by airplane or helicopter to infested areas just before male moths are anticipated to emerge from pupation (early to mid June). These plastic chips release pheromone slowly over the course of several weeks, inundating the area with pheromone and impairing the males’ ability to find the females. Under the right conditions, this treatment inhibits mating, causing the gypsy moth population to die out.
This treatment is only effective at lower population densities. If population densities are moderate to high, male moths will find female moths by chance, even without being able to follow the natural pheromone scent trails.
Nucleopolyhedrosis virus (Gypchek®)
Gypchek is a naturally-occurring virus that only targets gypsy moth. It is applied by airplane or helicopter. Under the right circumstances, spectacular epizootics can occur, leading to the collapse of gypsy moth populations.
Gypchek is only occasionally used to address gypsy moth infestations for two reasons. Because of the limited market, Gypchek is only manufactured by the US Forest Service and is available only in limited quantites. Also, like most viruses, Gypchek is highly communicable among individual larvae. For Gypchek to be successful, it must be passed from infected to uninfected larvae by physical contact. This only occurs at very high population densities.
Tibufenozide is a pesticide in the class of insect growth regulators. This means that, once exposed to tibufenozide, caterpillars are unable to successfully molt and grow. This prevents them from reaching maturity and reproducing. Tibufenozide may be applied by air or ground, but is most commonly used for ground treatments. It is successful on all population densities.
Like Mimic®, Dimilin® is an insect growth regulator which prohibits caterpillars from reaching maturity. Dimilin® may also applied by ground or air, but is most commonly applied from the ground. Like Mimic®, it is successful at all population densities.