Many home gardeners understand a sad truth about the corn earworm: the little critter loves sweet corn just as much as humans do.

It creates a yearly battle to fight back the pesky insect. The adult corn earworm moth lays eggs on developing corn silks and as soon as the eggs hatch, larval corn earworms go to work.

“Feeding starts at the tip of the ear and works down,” said Kansas State University horticulture expert Cynthia Domenghini.

Corn earworms feed on each other as well as the corn, so even though multiple eggs may hatch on an ear, usually only one is found in each ear, Domenghini said.

Protecting sweet corn from earworms comes with a couple time-dependent challenges. As corn silks continue to grow, any new silk that is left untreated can be targeted by earworms. Domenghini recommends applying insecticides every 2-3 days in order to be effective, “especially in early July, when peak flight of these moths usually appear,” she said.

Additionally, adult earworm moths prefer juicy silks instead of dry silks, so insecticide only needs to be applied the first two weeks of silking.

Which insecticides are most effective? For home gardeners, Domenghini recommends Spinosad, an organic insecticide. Another organic choice is mineral oil or other light horticultural oils.

To treat the corn, fill a medicine dropper ½ to ¾ full of the oil, then apply inside the silk end of the corn’s ear – where the tips of the silk begin to wilt and brown. Domenghini said the oil will kill any earworms present and prevent more earworms from entering the ear.

However, she said, take note that applying oil before the silk has begun to brown may lead to partially unfilled ears, as the oil will interfere with pollination.

Domenghini and her colleagues in K-State’s Department of Horticulture and Natural Resources produce a weekly Horticulture Newsletter with tips for maintaining home landscapes and gardens.Saving Sweet