Tritrophic Study Shows Effects of Bt Cotton on Herbivore and Its Predator

Scientist Rishi Kumar and colleagues conducted a tritrophic study to investigate the transfer of Cry proteins from Bt cotton to herbivore onion thrips (Thrips tabaci) and its predator insidious flower bug (Orius insidiosus). They also aimed to know the effects of the proteins on the predator's development, survival, and reproduction.

The average protein titers in Bt cotton leaves were 1,256 and 43,637 ng Cry1Ac and Cry2Ab per gram fresh leaf tissue, respectively. At the second trophic level, larvae of onion thrips reared on Bt cotton for 2 to 4 days had 22.1 and 2.1 percent of the Cry1Ac and Cry2Ab levels expressed in leaves, respectively. At the third trophic level, insidious flower bugs that fed on onion thrips larvae had 4.4 and 0.3% of the Cry1Ac and Cry2Ab protein levels, respectively, expressed in Bt plants.

Results showed that insidious flower bug's survivorship, time of nymphal development, adult weight, preoviposition and postoviposition periods, fecundity, and adult longevity were not significantly affected by Bt proteins. These results indicate that the insidious flower bug is not harmed by Bt cotton when exposed to Bt proteins through its prey. Thus, the insidious flower bug can continue to provide important biological control services in the cotton ecosystem when Bt cotton is used to control primary lepidopteran pests.

Read the research article at http://www.ingentaconnect.com/content/esa/jee/2014/00000107/00000003/art00006