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I .JOURNAL OF PESTICIDE REFORM1FALL 1994. VOL.14. NO.3 scrains.61.62 Devdopment of resistance oc- curs fascer when larger amounts of a pesti- cide are used, so that use of crop plants genetically-engineered to produce the B.t. toxin could dramatically increase the num- ber of B. t.-resistant insects. of the meal moth (Plodia interpunctella) . found that treatment with B.t. reduced the number of eggs produced by the parasitic wasp, and the percentage of those eggs that hatched.63 Production and hatchability of eggs of a predatory bug were also de- creased.63 On collards, aphid-eating flies in the family Syrphidae were reduced by Dipel treatment.64 Both B.t.tmebrionis and Dipel have caused mortality of. predatory spider mites.65 Dipd also has caused mortality of the cinnabar moth, used for the biological control of the weed tansy ragwort.66 Finally, B.t.i. has caused mortality of a moth (Synclita oblitera/is) that helps control aquatic weeds in Florida. 67 Other insects: Many insects that do not have as directly beneficial importance to agriculture are important in the function and structure of ecosystems. A variety of studies have shown that B.t. applications can disturb insect communities. Research. following large-scale B.t. applications to kill B.t.'s Ecological Impacts Some of the most serious concerns about widespread use ofB.t. asa pest control tech- nique come from the effects it can have on animals other than the pest wgetedfor con- trol. All B.t. products can kill organisms other than their intended targets. In turn, the animals that depend on these organ- isms for food are also impz.::ted. Beneficial insects: Many insects are not pests, and any pest management technique. needs to be especially concerned about those that are called beneficials, the insects that feed or prey on pest species. B.t. has im- pacts on a number of beneficial species. For example, studies of a wasp that is a parasite Figure 4 Development of Resistance to B.t. in the Tobacco Budwonn 50 40 .2 30 "@ CD (,) c: cu iii .~ 20 a: 10 o 10 Number of generations of selection Note: The resistance ratilil is determined by dividing the dose required to kill a B.l-resistant insect by the dose required to kill a su!lceptible insect. ... Source: Gould. F. et at 1992. Broad-spectrum resistance to Bacillus thuringiensis roxins in Heliothis virescens. Proc. Nat. Acad. Sci.89:7986-7990. 15 Under appropriate conditions. resistance to B.t. can develop quickly. After only seventeen genera- tions of selection. resistance to B.t. increased 50-fold in the tobacco budworm. . gypsy moth larvae in Lane County, Or- egon, found that the number of oak-feed- ing caterpillar species was reduced for three years following sprapng, and the number of caterpillars was reduced for two years.68 Similar results were found in a study of caterpillars feeding on tobacco brush fol- lowing a B.t.k. application to control spruce budworm in Oregon.69 In untreated areas, the number of species Was about 30 percent -higher, and the. number of caterpillars 5 times greater, than in B.t.k.-treated areas two weeks after treatment. The number of caterpillars was still reduced in treated areas the following summer. In Washington, B.t. applications in King and Pierce counties to kill gypsy moths reduced spring moth popu- lations by almost 90 percent.7o In addition, one rare species appeared to have been eradi- cated from the treatment wne, and moth populations were "heavily impacted in an area more than double that which was ac- tually sprayed" as moths moved into the treatment wne from surrounding areas.7o In West VIrginia, applications ofForay48B reduced the number of caterpillar species and the number of caterpillars. The year following application, the number of moth species and the number of moths were both reduceeJ..71 A recent (1994) study in four different Oregon plant cornmunities found . that total weight of caterpillars was reduced between 90 and 95 percent by B.t. treat- ment; the number of caterpillars was re- duced by 80 percent; and the number of caterpillar species was reduced by over 60 percent.72 Aquatic insects are also affected by B.t. treatments. Canadian studies found thac certain stream insects (Simulium vittatum and T amiopteryx nivalis) were killed by ap- plications of Thuricide and Dipd respec- tivdy.73.74 Midges. (chironomids) have re- peatedly been shown to be killed by B.t.i.75-77 Birds: Because many birds feed on the caterpillars and other insects affected by B.t. applications. it is not surprising that impacts ofB.t. sprapng on birds have been documented. In Lane County, Oregon studies of chickadees following a gypsy moth spray program found that birds nest- ing in B.t.-treated areas brought fewer cat- erpillars to their nests than did birds nest- 18 NORTHWEST COALITION FOR ALTERNATIVES TO PESTICIDES/NCAP P. O. BOX 1 393. E U G ENE. 0 REG 0 N 97440 I (503) 344 - 5044