Keep an Eye Out for Earworms

Corn earworm moths may move north earlier and in higher numbers.

Published on: Jul 2, 2010
Corn earworms are showing up earlier and in heavier numbers than usual in parts of the South this season. That will increase risk for more northerly corn fields later this summer.

That’s the bottom line of a new analysis by the Insect Migration Risk Forecast, developed by independent climatologist and meteorologist Mike Sandstrom. The IMRF analyzes moth trapping data and weather patterns to predict the annual northern migration of corn earworms from the South.

Sandstrom relies on university data as well as input from Monsanto field representatives to monitor earworm activity. Then, he overlays weather information, including wind flow and precipitation, to forecast migration patterns. 

Weather plays a critical factor, as a southerly flow associated with high- and low-pressure cells carries the moths to the north. 'This gives growers a proactive approach to insect management, especially during the peak periods of July and August in the Midwest when cornfields are most at risk,' he says. IMRF is sponsored by Monsanto. Learn more about the program at

Daily proactive forecasting is provided to identify corn growing regions of the U.S. at risk of experiencing earworm migration.  Forecasts are issued for one, two and three to five days in advance.

Multiple generations of corn earworm can invade cornfields from spring through September, causing the most damage when they synchronize with the corn silking.  Female moths lay their eggs on corn silks or green leaf tissue near the ear. When the larvae hatch, they move rapidly down the silk channel to feed on the ear tips or midsection of the ear. Besides yield loss, larvae can leave the corn susceptible to pathogenic fungi that can produce aflatoxin.