A question that I just received was, "What has the corn borer moth flight been like and what level of first-generation larval injury do I expect?" I met with the corn borer researchers, reviewed the moth captures, and discussed a projection concerning larval injury.

Female (left) and male European corn borers.

The researchers that have tracked moth flights over the years reported that the initial moth captures encouraged them to expect a good larval population. That is, the number of moths being captured was showing a gradual, steady increase. Then came the cold (at least "cool" depending on your preferences) spell the week before last. The moth fight activity dramatically declined with the cooler temperatures. While the moths sheltered in protected habitats, the diseases that infect them continued to run their course. Les Lewis, the ISU insect pathologist that works with the corn borer, suggests that the diseases will end the threat of heavy first-generation corn borer injury.

Remember that egg laying and larval survival are strongly influenced by local environmental conditions, so infestations in individual fields may deviate from this general prediction. The heavy rains that some areas experienced will further reduce larval survival, but other areas that have had quieter and drier weather may have more borers than the average of the state.