Garden Variety: How to handle sweet corn problems and pests

July is sweet corn season in Kansas. While some gardeners are already enjoying fresh ears of corn from their gardens, many are still waiting for kernels to develop or are battling corn earworms, raccoons and deer. Here are some tips for dealing with these problems and pests.

The most common com- plaint this summer is about ears being slow to fill out and kernels developing inconsistently across the ear. While the corn that develops is still tasty, serving it on the cob is less appetizing when there are large gaps between edible portions.

Usually, when corn ears fill out in this manner or not at all, the cause is a pollination problem. Planting layout, heat, drought and nutrient deficiencies, along with other environmental factors, can affect pollination. Nothing can be done to fix it once it has occurred, but steps can be taken to prevent the problem in the future.

First, avoid planting single rows or long, narrow blocks of sweet corn — the best layout is wide blocks of six or more rows. Second, ensure the corn is planted in a place that gets good air movement. Corn is pollinated by wind, so if the crop is protected on all sides, pollen may have a hard time getting to the silks, or the soft, hairlike strands growing out of the top of each ear.

Heat is usually unavoidable in a Kansas summer, but consider irrigating sweet corn over extended dry periods to combat drought stress. This is especially important during pollination. If nutrient deficiency is a possible factor, collect a soil sample and submit it for testing through K-State Research and Extension or a private lab. Samples can be taken and submitted any time through the year. Doing it now gives more time to remedy the problem (if one exists) before next spring.

Next up are corn earworms. These are the short, fat worms that feed on the kernels under the shucks. They will also feed on tomato fruit and a variety of other crops. Besides destroying the kernels they eat, their droppings make corn ears look a lot less appetizing.

In small patches of sweet corn, use mineral oil as a preventative for corn earworm. Apply a few drops of oil to the tip of each ear as the silks begin to dry. An eyedropper or syringe is helpful for application. For larger patches of sweet corn, another organic option is to use a product containing the active ingredient spinosad. There are several formulations and brand names on the market. There are also several conventional insecticides labeled for corn earworm control in sweet corn. Read and follow all label directions and pay close attention to harvest intervals — the amount of time after application that you should wait to harvest.

Raccoons and deer are also major problems for sweet corn growers. They seem to know by smell when the corn is almost ready and usually tear down the stalks, bite into individual ears of corn and strip the shucks back.

For raccoons, electric fences are recommended. Use two wires around the entire perimeter of the sweet corn patch. One wire should be about 4 inches off the ground, and the other wire should be about 12 inches off the ground.

For deer, there are a few more options. Add a wire to the raccoon fence at about 36 inches off the ground and tie flagging tape on it so deer can see it. You could also use hot tape (brightly colored tape with several electric strands in it that is also visible at night) for the high strand. If deer are problematic but raccoons are not, skip the lowest wire, but keep a wire at around 12 inches off the ground in addition to the 36-inch-high one.

Another option for deer is a nonelectric fence. It should be about 8 feet tall to be effective.

A final option for deer is to use a repel- lent. These are products sprayed on or around the corn to make it smell or taste bad to deer. They will also make the corn smell bad to humans, and they usually need to be reapplied in short intervals or after rainfall. They may do the trick long enough to keep the deer away during harvest season, though.

— Jennifer Smith works in regulatory horticulture and has worked as a horticulturist for various government entities. She has experience in landscape design and maintenance and as an educator.


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