aerial insecticide application
John H. Ghent,
USDA Forest Service, Bugwood.org
Insecticides are the most common treatment for problem populations, and there are a number of commercial products registered for gypsy moth. Some products are available over the counter to private landowners, but most are restricted to commercial pesticide applicators. Because of the usual size of infestations, the remoteness of some areas, the size of trees, and issues of scale, most insecticide applications require special equipment as well as licensing and are coordinated through a local or state agency. Most of these are aerial applications, and ground-based treatments are difficult and expensive. In some cases, homeowner groups may choose to work together to obtain treatment contracts.
Commonly Used Tactics
The list below includes the compounds most often used in federal, state, and local programs as well as control strategies of interest that are not commercially available. Homeowners and landowners may choose from any of the registered insecticides.
- Bacillus thuringiensis var kurstaki (Btk) (Dipel®, Foray®, Thuricide®). Btk is a naturally occurring soil-borne bacterium that acts as a stomach poison in gypsy moth larvae. It is available as a variety of commercial products. Btk is specific to Lepidoptera (moth and butterfly) larvae.
- Diflubenzuron (Dimilin®). Diflubenzuron is an insect growth regulator and disrupts the ability of larvae to molt from one stage to another. In addition to insects, it also impacts other invertebrates which produce an external skeleton containing chitin.
- Tebufenozide (Mimic®, Confirm®). Like diflubenzuron, tebufenozide is an insect growth regulator and disrupts the normal molting process in larvae. This compound currently is legally registered against gypsy moth but is not yet one of the options for the Virginia cost-share program.
- Nucleopolyhedrosis virus (NPV) (Gypcheck). NPV is a naturally occurring virus that causes disease in gypsy moth larvae. It is not available commercially but is produced in small quantities by the U.S. Forest Service. It typically is used in areas where potential non-target impacts stemming from the use of Btk or Dimilin, such as the presence of threatened or endangered butterflies or moths, would be unacceptable. Gypcheck is most effective in high populations.
- Mating disruption (Disrupt II®, SPLAT®). This technique, not available to the general public, is used only in low-to-moderate density populations outside the generally infested area and is a control strategy of choice in the Slow the Spread Project (STS). The gypsy moth mating pheromone is formulated to be sprayed aerially and treated areas become saturated with the pheromone. When males emerge, they are unable to orient to a female and mating is severely reduced in the treated area. Though not a true insecticide, it has been very effective in the STS Project. It is 100% specific to gypsy moth with no negative impacts.
- Entomophaga maimaiga. E. maimaiga is a fungal pathogen of gypsy moth that was introduced from Japan. The fungal disease infects gypsy moth larvae and is effective at both high and low populations. Unlike the compounds mentioned above, E. maimaiga is not formulated for use as an insecticide. However, it appears to be established in all areas where gypsy moth is prevalent. The efficacy of this disease is very much dependent upon weather conditions, particularly in the spring.
Health and Environmental Impacts
old insecticide application method
No insecticide is 100% safe. That being said, the health and environmental impacts from insecticides used in the Virginia gypsy moth suppression program (Btk, Dimilin, and Gypcheck) are minor. Toxicity to vertebrates, including pets and humans, is negligible for these compounds, but there are some non-target effects for Btk, which can kill other moth and butterfly species, and for Dimilin, which can be toxic to invertebrates possessing an external skeleton. Gypcheck is specific to gypsy moth and has no negative environmental or health effects. One must also keep in mind that the gypsy moth itself has negative impacts on the environment and human health, and these must be balanced against any undesired effects of insecticidal treatment. For detailed information on these issues see the documents below:
- Virginia Gypsy Moth Suppression Project Environmental Assessment
- Control / Eradication Agents for the Gypsy Moth – Risk Comparison
- Human Health and Ecological Risk Assessment for Diflubenzuron (Dimilin)
- Human Health and Ecological Risk Assessment for Bacillus thuringiensis var. kurstaki (B.t.k.)
- National Pesticide Telecommunications Network Fact Sheet on Bacillus thuringiensis