Fresh sweet corn is one of the most decadent tastes of summer, tainted only by the common brown or green caterpillars known as corn earworms.

Besides feasting on the sweet raw kernels, corn earworms leave behind an unappetizing mess and can sometimes work their way down an ear of corn to ruin it completely. Controlling corn earworms requires careful attention to the sweet corn patch before corn is ready to harvest.

The time to control corn earworm is just as silks begin to dry. For beginning gardeners or first-time corn growers, silks are the soft, green strands hanging out the top of each corn ear. Silks mature from green to brown as kernels mature and are where the corn earworm adults lay their eggs.

Use an eye dropper, small squirt bottle or syringe to apply a few drops of mineral oil to the tip of each ear. Mineral oil is effective on recently hatched larvae only, and only one application per ear is needed.

For gardeners with larger stands of sweet corn, mineral oil applications may sound tedious. Another organic option is spinosad. Because there are multiple formulations of spinosad products available, read the label to find one including corn earworm and also look for the OMRI (Organic Materials Review Institute) label. Apply according to label instructions. Applications may also be limited to the highest ear on each stalk as they are the ones most commonly infested.

Bacillus thuringiensis (Bt) applications are sometimes recommended as an option for organic corn earworm control, but research shows controversial results in effectiveness. Bt is more effective on corn earworm when the caterpillars are feeding on the various other vegetables that serve as alternative food sources. Cooking oils are also sometimes recommended, but little information is available regarding their effectiveness compared with mineral oil.

Late-planted sweet corn and midseason varieties of sweet corn are usually less affected by corn earworm because of maturation after peak flight of the adult moth. Some midseason sweet corn varieties also have tighter husks than many early-season varieties, helping prevent infestation.

In commercial conventional production, growers may use a number of insecticides at regular intervals to kill newly hatched corn earworm larvae.

Corn earworms are found worldwide and feed on a variety of vegetables, although sweet corn is favored. Tomatoes and beans are the second-most commonly infested crops. When they feed on tomatoes, corn earworms are often called tomato fruitworms despite being the same insect. The caterpillars may take on a different hue when feeding on different vegetables too, appearing more green or gray when feeding in green tomato fruits or in beans.

The adult version of the corn earworm is a nondescript brown moth with a wingspan of about an inch and a half. Corn earworm moths are nocturnal and blow north from their overwintering sites on prevailing winds in June and July. One female moth may lay 3,000 eggs.

— Jennifer Smith is a former horticulture extension agent for K-State Research and Extension and horticulturist for Lawrence Parks and Recreation. She is the host of “The Garden Show” and has been a gardener since childhood. Send your gardening questions and feedback to features@ljworld.com.