A Change In The Scouting Forecast

Growers across our region received much needed rain and a moderation in temperature. The change in growing conditions has shifted our scouting priorities. We are scouting for foliar diseases in addition to insect pests, and we have seen rapid growth syndrome in corn.

Foliar diseases in corn
We are specifically scouting for gray leaf spot and northern corn leaf blight (NCLB). Gray leaf spot starts out as small pinpoint lesions surrounded by yellow halos which develop into long rectangular lesions as the disease progresses on susceptible hybrids. Gray leaf spot can be found on leaves, leaf sheaths and husks. NCLB has long, narrow, tan or grayish lesions. Southern rust has not been confirmed in Kentucky to date. Common and southern rust are easily confused, this Purdue Extension handout is helpful in distinguishing between common and southern rust.

  corn-disease-update-fig-3-gray-leaf-spotcorn-disease-update-fig-1-northern-leaf-blight
Gray leaf spot (left) and northern corn leaf blight (right)

European corn borer (ECB)
Continue to scout for European corn borer, especially in conventional corn. Scouting for first-brood injury should start when corn is in the whorl stage and foliar injury is present. Foliar feeding injury resembles shot holes. First-brood rescue treatment could be needed when 50 percent or more of stand is infested and larvae have not tunneled into the stalk. Larvae of the first-brood pupate in the stalks and emerge again as adult moths in late-July and early-August. These adults prefer to deposit their eggs on late-planted corn.

Rapid growth syndrome
Rapid growth syndrome is caused by a sharp acceleration in plant growth. This year we have an increased number of cases due to the abrupt shift from poor to good growing conditions. Corn leaves fail to unfurl correctly and the whorl becomes tightly wrapped and twisted. Newly emerged leaves are yellow, but will turn green once exposed to sunlight. Individual plant development can be delayed, overall yield should not be affected.

Give us a call if you have questions about what you’re seeing in your fields.

Terry, Dan, Rod and Dennis