Reduced Mythimna separata infestation on Bt corn could benefit aphids

Use of genetically engineered plants that express insecticidal Cry proteins derived fromBacillus thuringiensis(Bt) have been proven efficacious for managing lepidopteran pests. However, in some cases herbivores that are not targeted by theBttrait have increased in importance. It has been suggested that reduced caterpillar damage toBtcrops could lead to decreased levels of induced plant defensive compounds which might benefit other non-target herbivores. Here we investigated the potential effect of reduced damage by larvae ofMythimna separataon aphid populations inBtcorn. We compared the performance ofRhopalosiphum maidisfeeding on non-Btcorn plants that had been infested byM. separatalarvae or were uninfested. The results showed that caterpillar-infested corn plants significantly reduced the fitness ofR. maidisleading to a prolonged nymphal development time, reduced adult longevity and fecundity compared to uninfested plants. Consequently, the population growth rate of corn aphids feeding on caterpillar-infested corn plants was significantly lower than on uninfested plants. As expected, the aphids performed significantly better on Lepidoptera-resistantBtcorn than on non-Btcorn when plants were infested withM. separata, since the caterpillars caused very little damage to theBtplants. The current findings indicate that reducedM. separatainfestation could benefit aphid development inBtcorn.Btcorn has the potential to be commercialized in China in the near future and aphids and other non-target pests should be monitored in the farming fields.

Automated summary

The study showed that damage by Mythimna separata caterpillars on Bt corn plants reduced the fitness of Rhopalosiphum maidis aphids, leading to lower population growth rates. Aphids performed better on Bt corn when plants were infested with M. separata caterpillars. Therefore, reduced caterpillar infestation could benefit aphid development in Bt corn, which may be commercialized in China in the near future, necessitating monitoring of aphids and other non-target pests in farming fields.