In mid-August of this summer, I wasn’t hearing anything about aphids feeding on corn and I thought we weren’t going to see it this year. These aphids are highly erratic and so where and when they land are not well understood. But the last week of August, I started to hear from folks in northern and western Iowa that they were finding aphids in some fields. In early September, some fields had some pretty high numbers (plants with over 1,000 aphids!). Generally, aphids were concentrated around the ear, but could be found throughout the plant.
The honeydew and subsequent black sooty mold production has been variable this summer. I visited a field today with Field Agronomist Angie Rieck-Hinz, near Story City, IA and the edge plants had a mix of species (bird cherry oat and corn leaf). There was active biological control efforts, including lady beetles, lacewings and parasitoid wasps. Although there were plants in the dent stage with well over 500 aphids, the honey dew was minimal and mold was absent. This is somewhat surprising given the field was moisture-stressed.