Recent Articles from FoBR Newsletters
Draft Environmental Impact Statement
Effects Associated With Insecticide Treatments
Insecticide treatments available for use under all strategies in all parts of the country are formulations of Bacillus thuringiensis var. kurstaki, diflubenzuron, and the gypsy moth nucleopolyhedrosis virus product Gypchek.
Bacillus thuringiensis var. kurstaki
Bacillus thuringiensis var. kurstaki (B.t.k.), a bacterium that has insecticidal activity against caterpillars of moths and butterflies, is a variety of Bacillus thuringiensis (B.t.).
How People May Be Affected by B.t.k.
If directly exposed to B.t.k. spray, some individuals (most likely project workers) may develop minor irritation of the skin, eyes, or respiratory tract. These effects are relatively mild and transient. Additional effects are not likely, even in individuals with impaired immune systems. No allergic response to B.t.k. has been documented.
How the Environment May Be Affected by B.t.k.
Due to the relatively short insecticidal activity of B.t.k., the risks associated with its use are usually limited to the time immediately after application.
Nontarget Organisms
Some caterpillars of moths and butterflies may be adversely affected by exposure to B.t.k. Large caterpillars eat more vegetation than small ones and are more likely to consume B.t.k. The potential for exposure to B.t.k. and mortality increases with an increase in the application rate and greater height in the tree canopy, because most B.t.k. spray is deposited in the tops of trees. B.t.k. poses a risk primarily to caterpillars present in spring because it is applied at that time and has relatively short insecticidal activity. Not all of these caterpillars may be affected due to wide differences in response to B.t.k. among species. Total numbers of moths and butterflies may be temporarily reduced. Some species appear to be particularly susceptible to B.t.k. and populations may be eliminated from treatment areas.
Permanent changes in nontarget caterpillar populations am not likely following suppression projects, which usually consist of a single application of B.t.k. An exception might occur in an area that supports a small isolated population of moths and butterflies that are highly susceptible to B.t.k. If unaffected individuals of the same species are unlikely to or cannot physically migrate from untreated areas to the treated area, a single application of B.t.k. may haw a greater effect on the ability of those populations to recover.
Both the numbers and types of nontarget caterpillars may be reduced after multiple applications of B.t.k. in the same year, as is possible in eradication projects. These effects can persist for 1 year or longer.
The predominant effect of B.t.k. on some parasites of caterpillars is indirect through effects on their hosts. Caterpillars that are exposed to B.t.k. but do not die eat less, grow more slowly, and remain longer in the larval stage, increasing their susceptibility to parasites. Parasitism of the gypsy moth by at least two parasitic wasps increases in areas sprayed with B.t.k. Few other species or groups are affected.
Vertebrates that feed on caterpillars in spring will have a reduced number of prey on which to feed for a short time. Reductions in caterpillar numbers from application of B.t.k. my force a switch in diet for birds and mammals that eat them. In birds, the number of nesting attempts per year my be reduced, but the overall number of fledglings per breeding territory may not change. Bats that feed on night-flying moths in summer may have to expand their foraging territories and adjust their foraging habits temporarily.
Use of B.t.k. reduces the incidence of infection by the nucleopolyhedrosis virus in gypsy moth populations. B.t.k. reduces both the number of early stage caterpillars available for infection by the virus and the amount of virus released that can infect the residual gypsy moth population.
Forest Condition
B.t.k. reduces defoliation caused by all springfeeding caterpillars. As a result, its use is more likely to maintain the forest condition than change it.
Water Quality and Microclimate
By protecting tree, foliage, B.t.k. reduces the likelihood of changes in water quality and microclimate that might be associated with feeding by gypsy moth caterpillars.
Soil Productivity and Fertility
Changes in soil productivity and fertility due to B.t.k. are not likely. B.t.k. persists for a relatively short time, B.t. is known to occur naturally in soils worldwide, and applications of insecticides containing B.t. do not appear to increase levels of B.t. in soil. Some soil invertebrates may be affected by B.t.k, but additional research is needed to determine what effects, if any, this might have on rates of soil decomposition.
Diflubenzuron
Diflubenzuron (Dimillin), a chemical insecticide, interferes with the growth of some immature insects.
How People May Be Affected by Diflubenzuron
No human health effects are likely from exposure to diflubenzuron as it is used in gypsy moth projects. At very high exposures, increases in methemoglobin, an abnormal blood pigment that reduces the oxygen-carrying capacity of the blood, might be detectable. If other compounds that raise levels of methentoglobin-cigarette or other combustion smoke, carbon monoxide, nitrates in air or water-are present, the effect may be additive. A conservative estimate of cancer risk from exposure to diflubenzuron or 4-chloroaniline, a breakdown product of diflubenzuron, is less than one in 1 million over a lifetime.
How the Environment May Be Affected by Diflubenzuron
Diflubenzuron is persistent on vegetation throughout the growing season and may remain in leaf litter 1 year following a spray.
Nontarget Organisms
Moths and butterflies, grasshoppers, parasitic wasps, aquatic insects, bottom-dwelling crustaceans, and immature, free-floating crustaceans could be adversely affected from the lowest application rate of diflubenzuron used in gypsy moth treatment Projects (0.25 oz. active ingredient per acre). Higher application rates reduce populations even more and affect more types of species groups. More aquatic organisms could be affected at the highest application rate registered for use (1.0 - active ingredient per acre).
Terrestrial Orgamisms-Moths, butterflies, and grasshoppers my be affected in both the upper and lower tree canopy in spring and fall. Most diflubenzuron spray is deposited in the upper canopy, and the amount of diflubenzuron residue begins to diminish after spraying in spring. As a result, the population reduction is greater for species that feed in the upper canopy.
Because Diflubenzuron can kill caterpillars that serve as hosts, parasitic wasps of caterpillars may be indirectly affected. Diflubenzuron can have different effects on different species of parasites of nontarget insects. Of predators that eat prey contaminated with diflubenzuron, more of those in immature stages, such as lacewings, die than do adults. The adults, such as ladybird beetles, may produce fewer offspring.
Ground spiders could be directly affected by diflubenzuron applications or indirectly by a reduction in prey. Overall species diversity would remain unchanged.
Vertebrates, beetles, and earthworms are not likely to be affected by exposure to diflubruzuron.
Birds are not directly affected by exposure to diflubenzuron. Some insectivorous species may show subtle changes, such as a switch in diet, reduced fat loads, and expanded foraging territories. Similar changes may occur in bats that feed primarily on moths and butterflies.
Aquatic Organism-Aquatic organisms may be affected by diflubenzuron treatments in both undeveloped forest areas and developed residential areas. Bottom-dwelling insects may be affected in all habitats except ponds in undeveloped forest areas, which have the lowest concentrations of diflubenzuron. Freefloating crustaceans may be less affected in undeveloped areas. Mollusks do not appear to be at risk.
Fish are not likely to be directly affected from exposure to diflubenzuron as it is used in gypsy moth projects. Fish could suffer indirect effects through a reduction in prey but would likely compensate for this by eating other organisms.
Multiple Applications and Recolonization-The effects on most organisms from exposure to diflubenzuron applied 1 to 2 weeks apart, as in eradication projects, would be similar to one treatment at twice the application rate. Consecutive annual applications of diflubenzuron may affect invertebrates in leaf litter more than would a single application, because some diflubenzuron residues would persist into the following spring when the next treatment would be applied.
Some generalizations can be made about the risk of eliminating nontarget invertebrates from an area treated with diflubenzuron:
Forest Condition
Diflubenzuron is not poisonous to plants and has no direct effect on them. Diflubenzuron may indirectly help maintain existing forest condition by reducing gypsy moth populations and protecting tree foliage.
Water Quality
Diflubenzuron may reduce numbers of two groups of stream invertebrates: those that process particulate organic matter from plant and animal remains, and those that feed on algae. Changes in water quality due to reductions of organisms in these groups, however, have not been observed.
Microclimate
Diflubenzuron indirectly helps maintain the existing microclimate by reducing the amount of defoliation by the gypsy moth and other insect defoliators.
Soil Productivity and Fertility
Earthworms are not at risk from diflubenzuron. Other invertebrates in leaf litter, particularly mites and ground dwelling spiders, may be affected by exposure to diflubenzuron, but decomposition rates of leaf litter do net seem to be affected.
Nucleopolyhedrosis Virus (Gypchek)
The nucleopolyhedrosis virus, which occurs naturally, is specific to the gypsy moth. Gypchek is an insecticide product made from the gypsy moth nucleopolyhedrosis virus.
How People May Be Affected by Gypchek
Irritation of the eyes, skin, and respiratory tract is possible from exposure to Gypchek, but this possibility cannot be assessed due to limitations in the available data. Because Gypchek contains gypsy moth parts, irritant effects might be similar to those caused by the gypsy moth itself. Individuals with allergies may be at greater risk of developing irritation. Workers are more likely to be affected than the general public because their exposure will be higher,
How the Environment May Be Affected by Gypchek
The gypsy moth virus is not known to affect organisms other than the gypsy moth, and no change in nontarget species or their populations is likely from the use of Gypchek.
Changes in forest condition, water quality, microclimate, and soil productivity and fertility from the use of Gypchek will be minimal compared with those that otherwise would occur from feeding by the gypsy moth.
Click Here for information on MIMIC
