@article{johnson_gould_kennedy_1997, title={Effects of natural enemies on relative fitness of Heliothis virescens genotypes adapted and not adapted to resistant host plants}, volume={82}, ISSN={["0013-8703"]}, DOI={10.1046/j.1570-7458.1997.00133.x}, abstractNote={Abstract}, number={2}, journal={ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA}, author={Johnson, MT and Gould, F and Kennedy, GG}, year={1997}, month={Feb}, pages={219–230} }
 @article{johnson_1997, title={Interaction of resistant plants and wasp parasitoids of tobacco budworm (Lepidoptera: Noctuidae).}, volume={26}, ISSN={["0046-225X"]}, DOI={10.1093/ee/26.2.207}, abstractNote={The interactions of 2 species of parasitoid wasps, their host, Heliothis virescens (F.), and transgenic tobacco producing a low concentration of Bacillus thuringiensis Berliner toxin were investigated in field tests. Campoletis sonorensis (Cameron) and toxic plants each decreased survival of larvae during the first 6 d on plants. C. sonorensis and toxic plants acted synergistically in combination, decreasing larval survival beyond the level expected for an additive interaction. Cardiochiles nigriceps Viereck did not significantly reduce 6-d survival of host larvae and did not interact with plant toxicity. Parasitism of H. virescens exposed for 1 d to natural populations of the same parasitoids was highly variable from day to day, and also varied between years. In 1990, C. sonorensis was the more prevalent species; in 1991, C. nigriceps was dominant. In 1990, single-day parasitism of neonates by C. sonorensis was lower on toxic plants than nontoxic plants. This result, which contradicted previous findings of increased parasitism among larvae exposed for several days on toxic plants, probably was caused by differences in initial behavior of larvae on toxic versus nontoxic plants. In 1991, position of larvae on plants did not affect parasitism by C. sonorensis ; however, parasitism by C. nigriceps was significantly higher among larvae collected from exposed positions on leaves compared with apical buds. Patterns of daily parasitism of 1- to 8-d-old larvae were extremely different for the 2 parasitoids: vulnerability to C. sonorensis among host larvae on nontoxic plants began to decline after 3 d; whereas, parasitism by C. nigriceps increased over the 1st few days and remained high through 8 d.}, number={2}, journal={ENVIRONMENTAL ENTOMOLOGY}, author={Johnson, MT}, year={1997}, month={Apr}, pages={207–214} }
 @article{johnson_gould_1992, title={INTERACTION OF GENETICALLY ENGINEERED HOST PLANT-RESISTANCE AND NATURAL ENEMIES OF HELIOTHIS-VIRESCENS (LEPIDOPTERA, NOCTUIDAE) IN TOBACCO}, volume={21}, ISSN={["0046-225X"]}, DOI={10.1093/ee/21.3.586}, abstractNote={Field experiments were conducted to examine interactions of Heliothis virescens (F.), its natural enemies, and tobacco plants engineered to express low levels of Bacillus thuringiensis Berliner toxin. Survival of H. virescens larvae was measured in response to four treatments: (1) toxin-producing plants exposed to natural enemies, (2) toxin-producing plants caged to exclude enemies, (3) toxin-free plants exposed to enemies, and (4) toxin-free plants caged to exclude enemies. B. thuringiensis toxin mediated resistance caused a significant decrease in first-instar survival, and natural enemies caused a significant decrease in third-instar survival. Survival of uncaged first instars as a proportion of survival of caged first instars was significantly lower on toxic plants than control plants, indicating synergism of resistance and natural enemies. Among collections of artificially infested larvae, parasitism by Campoletis sonorensis (Cameron) was significantly higher on toxic plants than on control plants, another indication of synergism. Among collections of wild larvae and larvae censused in the field, parasitism usually did not differ between plant lines. Larval development of H. virescens was significantly slower on toxic plants than on control plants in two out of five trials. Prolonged vulnerability to natural enemies appeared to provide a mechanism for synergism. However, synergistic increases in mortality and parasitism were detected in two trials when development rates on toxic plants and control plants were equal, indicating existence of another mechanism. B. thuringiensis toxin-mediated partial resistance appeared compatible with natural enemies for control of H. virescens . However, a simulation using a theoretical population genetic model suggested that synergism of the level measured in this study could accelerate pest adaptation to resistant plants.}, number={3}, journal={ENVIRONMENTAL ENTOMOLOGY}, author={JOHNSON, MT and GOULD, F}, year={1992}, month={Jun}, pages={586–597} }