Corn earworm caterpillar feeding on sweet corn tassel
New research from the University of Maryland indicates that corn earworm, also known as tomato fruitworm, has developed resistance to the Cry1 Bt toxins present in some sweet corn hybrids. Based upon Galen Dively’s twenty-one years of research comparing non-Bt sweet corn varieties with Bt varieties in plot studies, the proportion of damaged ears in Bt varieties has dramatically increased over that time.
Syngenta sweet corn hybrids with Attribute® technology expressing Cry1 Ab toxins in 1996 showed less than 10% ear damage. Those hybrids with Attribute® in 2016 averaged 84% ear damage. Similarly, the amount of damaged area per ear had tripled.
Seminis produced sweet corn hybrids with Performance SeriesTM containing Cry1 A.105 and Cry2 ab for worm control. When some of these hybrids were first evaluated in 2010 they provided 100% control of fall armyworm and 95% control of corn earworm. In 2016, six plantings at research farm sites of these hybrids averaged 67% damaged ears.
