Bt cotton producing Cry1Ac and Cry2Ab does not harm two parasitoids, Cotesia marginiventris and Copidosoma floridanum

Authors: TIAN, J - Zhejiang Academy Of Agricultural Sciences; WANG, X - Yangtze University; CHEN, Y - Zhejiang Academy Of Agricultural Sciences; ROMEIS, J - Agroscope; Naranjo, Steven; Hellmich Ii, Richard; WNAG, P - Cornell University; SHELTON, A - Cornell University

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2017
Publication Date: 1/10/2018
Publication URL: http://handle.nal.usda.gov/10113/5931519
Citation: Tian, J.C., Wang, X.P., Chen, Y., Romeis, J., Naranjo, S.E., Hellmich, R.L., Wnag, P., Shelton, A.M. 2018. Bt cotton producing Cry1Ac and Cry2Ab does not harm two parasitoids, Cotesia marginiventris and Copidosoma floridanum. Scientific Reports. 8:307.

Interpretive Summary: Transgenic Bt crops that produced proteins toxic to caterpillar pests have been widely adopted in many countries. There remains concern about the environmental impacts of these crops, including their effects on arthropods that the plants were not specifically designed to impact (non-targets). A set of laboratory studies were conducted to examine to potential effects of a Bt cotton that produces two Cry proteins )Cry1Ac and Cry2Ab) on two parasitoids (Costisia marginiventris and Copidosoma floridanum) that are considered beneficial insects because they attack various caterpillar pest species. When caterpillar pests feed on Bt cotton they are negatively affected and so non-target evaluations need to take this into account when studying the parasitoids that use these caterpillars as hosts. In order to eliminate the confounding effects of this host quality effect, we used caterpillars that have natural resistance to the Bt proteins and are unaffected when feeding on the plant. These tri-trophic studies confirm that Cry1Ac/Cry2Ab cotton had no significant impact on development, success of parasitism, survival and adult longevity of C. marginiventris. Similarly, this Bt cotton had no significant impact on the development, weight and fecundity of C. floridanum. Our studies further verified that freeze-dried Bt crop tissue maintained its insecticidal bioactivity when incorporated into an artificial diet, demonstrating that this is a feasible method for evaluating effects of Bt proteins. C. floridanum, or similar species that consume their entire host, should be considered useful surrogates in risk assessment of on non-target arthropods to Bt crops. The results are of interest to researchers, environmental regulators and the general public concerned about the safety of transgenic crops.

Technical Abstract: Cabbage looper, Trichoplusia ni, is an agricultural pest that feeds on >160 plant species in 36 families and is an important lepidopteran pest on many vegetable and greenhouse crops and some field crops. Although there are no commercial Bt vegetable or greenhouse crops, T. ni is a target of Bollgard II, which produces Cry1Ac and Cry2Ab and is widely cultivated in the USA. We expand on previous work that examined the effect of Bt crops on parasitoids using Bt-resistant lepidopteran population as hosts. Cry1Ac/Cry2Ab-resistant T. ni larvae were used to eliminate host quality effects and to evaluate the direct effects of Cry1Ac/Cry2Ab cotton on the parasitoids Copidosoma floridanum (Ashmead) and Cotesia marginiventris (Cresson). These tri-trophic studies confirm that Cry1Ac/Cry2Ab cotton had no significant impact on development, success of parasitism, survival and adult longevity of C. marginiventris when using Bt-resistant T. ni fed on Bt cotton. Similarly, this Bt cotton had no significant impact on the development, mummy weight and fecundity of C. floridanum. Our studies further verified that lyophilized Bt crop tissue maintained its insecticidal bioactivity when incorporated into an artificial diet, demonstrating that this is a feasible method for evaluating effects of Bt proteins. C. floridanum, or similar species that consume their entire host, should be considered useful surrogates in risk assessment of on non-target arthropods to Bt crops.