1/3/12, 11:35

Tritrophic interactions among Bt maize, an insect pest and entomopathogens: effects on development and survival of western corn rootworm

El presente estudio plantea las interacciones tritróficas entre el maíz Bt, la plaga Diabrotica sp y organismos entomopatógenos. La resistencia de la planta hospedante (conferida por ingeniería genética, el maíz Bt) aumenta la mortalidad del insecto y retrasa el desarrollo; sin embargo, este retraso del desarrollo de la plaga no aumenta la mortalidad de los entomopatógenos, los cuales matan al insecto de una manera diferente a como lo hace la toxina que produce el maíz Bt. Sin embargo, los efectos independientes y complementarios observados ilustran la compatiblidad potencial de entomopatógenos presentes en naturalmente en el agroecosistema con el maíz Bt, para regular las poblaciones de plagas y la posibilidad de aumentar las defensas de las plantas en las raíces por beneficiarse de los entomopatógenos.

J.L. Petzold-Maxwell, S.T.Jaronski & A.J. Gassmann

Ann Appl Biol, 160: 43–55 (2012)

 

Agricultural systems often provide a model for testing ecological hypotheses, while ecological theory can enable more effective pest management. One of the best examples of this is the interaction between host-plant resistance and natural enemies. With the advent of crops that are genetically modified to produce insecticidal toxins from the bacterium Bacillus thuringiensis (Bt), a new form of host-plant resistance has been introduced to agroecosystems. How Bt crops interact with natural enemies, especially insect pathogens in belowground systems, is not well understood, but provides a unique opportunity to study below-ground tritrophic interactions. In this study, we used two species of entomopathogenic fungi and three species of entomopathogenic nematodes to determine how this community of soil-borne natural enemies might interact with Bt maize (event 59122, expressing the insecticidal protein Cry34/35Ab1) to affect survival and development of western corn rootworm (Diabrotica virgifera virgifera), which is an obligate root feeder and a serious pest of maize. We ran two experiments, one in a greenhouse and one in a growth chamber. Both experiments consisted of a fully crossed design with two maize treatments (Bt maize and non-Bt maize) and two entomopathogen treatments (present or absent). The community of entomopathogens significantly increased mortality of western corn rootworm, and Bt maize increased larval developmental time and mortality. Entomopathogens and Bt maize acted in an independent and additive manner, with both factors increasing the mortality of western corn rootworm. Results from this study suggest that entomopathogens may complement host-plant resistance from Bt crops.