Corn Earworm

What it looks like

Adults are tan to olive moths about 1.5 inches across. Larvae vary from green to brown to pink, with light and dark stripes and tiny spines, up to 1.5 inches long.

Damage

Caterpillars feed on corn silk and kernels at the ear tip, leaving frass and mold. On tomatoes they are called tomato fruitworms and bore into the fruit. Damaged produce often rots.

How nematodes help

Full-grown caterpillars drop to the ground and turn into pupae 2 to 4 inches deep in the soil, where nematodes can reach them. In the South, the pupae spend the winter in the soil.

S. riobrave (a species BioLogic doesn't sell), found naturally in Texas corn fields, has given the best results. USDA research found strong results when nematodes were applied just as the caterpillars left the ears to pupate. In lab tests, S. carpocapsae (the nematode in Ecomask) and Heterorhabditis nematodes killed caterpillars that were getting ready to pupate. There is less field research on S. feltiae (the nematode in Scanmask), so time it for when the caterpillars are in the soil.

In university research, the timing that worked best was mid to late summer, often July to September, when the caterpillars leave the ears and fruit to pupate. A fall treatment after harvest also reaches the pupae.

How to apply

Treat with Scanmask. Ecomask also works.

When: June to August.

Where: Spray the soil around and under corn and tomato rows, and the ground where fallen ears and fruit lie.

See How to apply for step-by-step directions, or use the calculator on the Scanmask Spray page to see how much you need.