Insect resistant Bt rice lines have been developed in China. Field surveys
showed that Bt rice plants have less rice planthoppers (Nilapavata lugens)
than non-Bt rice, although planthoppers are not targeted by the insecticidal
proteins in Bt rice. Thus, Xingyun Wang of the Chinese Academy of
Agricultural Sciences and colleagues conducted an investigation about the
mechanisms underlying this phenomenon.

Results showed that the low number of planthoppers on Bt rice is linked to
decreased caterpillar damage. Laboratory, field-cage, and open-field
experiments showed that rice planthoppers had no feeding preference for
undamaged Bt or non-Bt plants, but had a strong preference for
caterpillar-damaged Bt or non-Bt plants. Further analyses showed that
caterpillar damage caused the release plant volatiles attractive to
planthoppers.

The researchers recommended the use of non-Bt rice refuges to serve as a
trap crop for planthoppers and also to delay the development of Bt
resistance.

[onlinelibrary.wiley.com]