Resistance parasitoids

Toxic substances acquired from the host plaint may provide resistance to parasitoids (24), pathogens (25), and predators (45). By avoiding some toxins in plant material and selecting superior food tissues, insects feeding on variable hosts may become more susceptible to some enemies. Of course, other substances in preferred tissues may still be toxic to certain of these enemies, but this is less likely than it would be were plant compounds uniformly encountered by the host insect. 

Hagen, K. S. (1986). Ecosystem analysis plant cultivar (HPR), entomophagous species and food supplements. In Interactions of Plant Resistance and Parasitoids and Predators of Insects, eds. D. J. Boethel and R. D. Eikenbary, pp. 153-197. New York John Wiley Sons. 

Duffey, S. S., Bloem, K. A. and Campbell, B. C. 1986. Consequences of sequestration of plant natural products in plant-insect interactions. In Boethel, D. F. and Eikenbary, R. D. (Eds.), Interactions of Plant Resistance and Parasitoids and Predators of Insects. Florwood, Chichester, England. 31-60... 

Baker, J.E., Stability of malathion resistance in two hymenopterous parasitoids, /. Earn. Entomoi, 88, 232,1995. 

Another success in resistance management involves not just a single key pest species, but a whole complex of phytophagous arthropod pests of apple in the United States (39). It also focuses on resistance management of a number of beneficial arthropod predators and parasitoids that provide significant biological control of a variety of secondary pests on this crop. 

Several parasitoids have been selected for pesticide resistance. 

Some exogenous plant activators inducing resistance to herbivores are further examples of chemical biotechnology. MJA, " BTH, > TDL and NCI are all reported to be able to enhance herbivore resistance. It was found that treatment with BTH increased the attractiveness of maize plants to parasitic wasp. The parasitic wasps are parasitoids of various animals, mainly other arthropods. Many of them are considered beneficial to humans because they control populations of agricultural pests. 

Interestingly, plants treated with the plant activators did not show any consistent increase in volatile emissions. On the contrary, treated plants released less herbivore-induced volatiles such as indole, which has been reported to interfere with parasitoid attraction. The results support the yet undetectable and unidentified phenomena that plant activators are major factors for parasitoid attraction, and these attractants may be masked by some of the major compounds in the volatile blends. This study confirms that activators of pathogen resistance are compatible with the biological control of insect pests and may even help to improve it. 

Tridecanone—Glandular Trichome-Mediated Insect Resistance in Tomato Effect on Parasitoids and Predators of Helwthis zeo... 

Some of the complex ecological interactions mediated by plant defenses are illustrated by the resistance of a wild tomato, Lycopersicon hirsutum f, glabratum C, H. Mull, accession PI 134417, to Manduca sexta (L,), the tobacco hornworm, and its effects on several predators and parasitoids of Heliothis zea (Boddie), the tomato fruitworm. 

Because 2-tridecanone-mediated resistance to sexta and L. decemlineata is genetically distinct from the lamellar-based resistance to zea, it would be possible to develop tomato cultivate resistant to sexta and decemlineata but susceptible to zea. On such cultivate, the 2-tridecanone-mediated induction of elevated tolerance to some insecticides might make control of zea more difficult (55, 58). The severity of H. zea as a pest problem on such cultivate would be further exacerbated if 2-tridecanone associated with the resistant foliage seriously interfered with insect parasitoids and predators important in suppressing natural populations of zea. Because of its occurrence in the foliar glandular trichomes, and because of its broad spectrum toxicity to insects, we considered it likely that parasitoids and predaceous insects searching the resistant foliage for prey would be exposed to potentially toxic levels of 2-tridecanone. 

Although parasitism of zea larvae on tomato is variable and often low in North Carolina, we have consistently observed lower levels of larval parasitism by an array of parasitoids on plant lines selected for elevated levels of 2-tridecanone-mediated resistance to M, sexta (Table VI) (64). To investigate the causes of reduced parasitism, we focused on two species of larval parasitoids Campoletis sonorensis (Cameron), an ichneumonid, and Archytas marmoratus (Townsend), a tachinid. 

In field cage studies in which zea larvae on several plant lines were exposed to adult parasitoids (one plant line per cage), percent paras itization by both species was significantly lower on BC2, (a backcross ((L, esculentum x PI 134417) x PI 134417) line with intermediate levels of 2-tridecanone and glandular trichome density), and PI 134417 than on L. esculentum and the Fi hybrid (L. esculentum X PI 134417) (Table ViTT. This pattern reflects levels of 2-tridecanone-mediated resistance to sexta. These data indicate that fewer zea larvae are parasitized on the more resistant plant lines but do not indicate whether this is due to elevated densities of glandular trichomes or methyl ketones, or both. 

Because of their life histories, larvae of both parasitoids directly contact the foliage of the food plants of their host larvae. Thus, potential exists for both to be affected directly by the methyl ketones present in the glandular trichomes of the resistant plants. 

Tridecanone/glandular trichome-mediated resistance of L hirsutum f. glabratum PI 134417 to sexta and decemlineata adversely affects an array of parasitoids and predaceous insects that are important natural enemies of the tomato fruitworm, zea. These natural enemies represent a diversity of life histories and are affected by the defenses of PI 134417 in different ways. Because the resistance of PI 134417 decreases the parasitization rates and increases mortality of immatures of the three parasitoid species... 

Interactions of Plant Resistance and Parasitoids and Predators of Insects. Ellis Horwood Ltd., Chichester. 

Kauffman, W, C. and G. G. Kennedy, 1989c. Toxicity of alle-lochemicals from wild insect-resistant tomato Lycopersicon hirsutum f, glabratum to Campoletis sonorensis, a parasitoid of Heliothis zea. J. Chem, Ecol. 15 2051-2060,... 

Salt, G. (1968) The resistance of insect parasitoids to the defense reactions of their hosts, Biol. Rev. Camb. Phil., 43, 200-32. 

Salt, G. (1970b) Experimental studies in insect parasitism. XV. The means of resistance of a parasitoid larvae. Proc. R. Soc. Lond. Sen. B, 176, 105-14. 

Vinson, S. B. (1977b) Insect host responses against parasitoids and the parasitoid s resistance with emphasis on the Lepidoptera-Hymenoptera association. Comp. Pathobiol., 3, 103-25. 

---