Field-Evolved Resistance to Bt Maize by Western Corn Rootworm

Bt crops are planted on millions of hectare each year, contributing to the reduced use of traditional insecticides. However, there is a possibility that pests would evolve resistance to the crops after extended use.

Scientist Aaron Gassman and colleagues at the Iowa State University have reported that fields identified by farmers as having high rootworm feeding injury to Bt maize contained populations of western corn rootworm. Fields with high rootworm feeding contained Cry3Bb1 maize, which has been planted in those fields for the last three years. A significant positive correlation was found between the number of years Cry3Bb1 maize had been grown in the field and the survival of rootworm populations on Cry3Bb1 maize bioassays. No cross resistance was found in other crops with different Bt proteins.

According to the researchers, insufficient planting of refuges and non-recessive inheritance of resistance may have caused the reported field-evolved resistance. Thus, it is suggested that more improvement in resistance management in the use of Bt crops may be needed to prevent such conditions.

Read the open-access article at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0022629.