A couple of weeks ago, Corn Leaf Aphids were found in corn fields in Calhoun and Jackson counties.  Field populations ranged from 1-3% infested plants to 40% infested plants and infested plants had 1,000-3,000 aphids per leaf in the top three leaves on the plant. Most fields were already tasseling and silking but some were pre-tassel.

By the time I saw them in the field (May 2), there was already 10-20% parasitized aphid mummies and large lady beetle larvae of at least two lady beetle species.

A research trial was conducted to evaluate Bifinthrin efficacy in controlling the aphids. At 2 days after treatment (DAT), Plants averaged 1682 and 1997 aphids per leaf in treated and untreated plots, respectively. Two days later, at 4 DAT, the aphid numbers had dropped significantly to 152 and 425 aphids per leaf for treated and untreated plants.

The field is still being followed and measurements are planned to determine the effect of the aphids on the pollination and grain production by comparing plants with different aphid levels.

To summarize what we have learned so far, the natural enemies reduced aphid numbers by 75% over 4 days.  Little honeydew was produced by the corn leaf aphid compared to other aphid species on other crops such as the sugarcane (sorghum) aphid in grain sorghum. Bifinthrin provided suppression of the aphids but not what I would consider good control.

More to come.