2015 marks the 40th year of my career as an entomologist and I still am surprised on a regular basis by how insects behave. I put out a corn earworm pheromone trap on May 14 and immediately caught 7 moths that night. Over the next three nights, I caught 36 moths. Typically, the few earworms that we would expect to overwinter here in west central Indiana would emerge about June 20. It has not been an unusually warm spring, to say the least, so it is unlikely that those moths emerged locally. The other possibility is migration from southern areas. Earworm moths often migrate in on storm fronts from the south. However, when moths are blown hundreds of miles on storm fronts, their wings usually get a little tattered. The moths I’ve been catching look pristine, as if they just emerged. So, the bottom line is that I have no idea what’s going on.
So, how does this early population of earworms affect vegetable growers? Earworms are very polyphagous, feeding on many plant species, both crop and non-crop. So, the female moths are going to lay their eggs somewhere. My colleague Rick Weinzierl from the University of Illinois has reported earworm damage on strawberries. High tunnel or greenhouse tomato growers need to beware, since the other name for corn earworm is tomato fruitworm. Growers who have very early sweet corn may see earworm larvae feeding on the leaves. This damage is usually pretty minor, but growers need to keep an eye out for unusual damage.