University of Illinois Extension

Six Pests You Should Know

Cucumber BeetleGardening is an adventure filled with challenges, says Ron Wolford, University of Illinois Extension horticulturist.

"One of the things I really like about vegetable gardening is the challenges that occur every gardening season," said Wolford. "One of those challenges is insect pests. In my 58 years of gardening, I have encountered a number of insect pests in the vegetable garden. The following are the ones that keep coming back year, after year, after year."

The cucumber beetle is a black and yellow spotted or striped one-fourth inch long beetle. It is a chewing insect feeding on the flowers, stems and fruit of vegetables, flying from one plant to another. Cucumber beetles will attack cucumbers, muskmelon, pumpkin, squash and watermelon. Cucumber beetles also can infect plants with a bacterial wilt disease.

"The disease will show up just as fruit is beginning to form," he said. "Almost overnight the entire plant will wilt. To control the disease, you must control the cucumber beetle. Control with row covers until the plant starts to bloom."

Aphids are tiny, wingless sucking insects less than one-eighth inch long. They are slow moving and are most often found on the undersides of leaves. They range in color from light green to black. They will attack a variety of vegetable crops including beans, cabbage, squash and tomatoes.

"One sign of aphids is a clear, sticky substance they exude called 'honeydew' that you will see on leaves," said Wolford. "Ants are attracted to the 'honeydew' as a food source. Aphids suck the plant juices out of the plant causing leaves to curl and yellow. Aphids can reproduce with or without a mate.

"Scouting for aphids in your garden will help to keep populations from exploding. Aphids can be washed off plants with a strong stream of water. Insecticidal soap can also be used as a control for aphids."

Squash vine borers can be devastating to zucchini. Borers hatch from reddish-brown eggs that are laid at the base of the stem from mid-June through July. The borer is a one inch long white larvae that bores into the stems of zucchini, pumpkins and melons. This boring action cuts off the water supply to the rest of the plant causing it to wilt.

Cabbage Loopers "Besides wilting, signs of a borer infestation include holes at the base of the plant with an orange sawdust-like material called frass," he said. "Control includes planting early to get a crop before the eggs hatch or covering the plant with a row cover until flowering occurs." "My favorite vegetable insect is the tomato hornworm," he said. "It would make a great monster in some low budget horror film."

Tomato hornworms can grow up to five inches long. They have orange antennas that stick out when they are disturbed. A few of them can strip a tomato plant of all its leaves in a couple of days. If you see a hornworm with what looks like eggs on its back, don't worry, that worm is the walking dead. It has been attacked by a parasitic wasp. The wasp lays its eggs in the worm, the eggs hatch and the larvae eat their way out of the worm to pupate. Handpicking is an easy and effective method of control.

Have you ever seen a white butterfly fluttering around the vegetable garden? That butterfly is the adult of the imported cabbage worm. The imported cabbageworm is a velvety green 1 1/4-inch long caterpillar.

Another common worm in the vegetable garden is the Cabbage looper, a 1 1/2-inch long smooth green caterpillar. Cabbage loopers are easily identifiable as they crawl by doubling up to form a loop. Both of these worms attack heads of cabbage and other cole crops. For control, you can either handpick the worms or cover the plant with row covers. Wolford offered some tips on controlling insects.

"A few holes in plant leaves or a few insects on a plant does not necessitate spraying chemicals," he said. "If you do use chemical controls read and follow all label directions and precautions. Contact your local University of Illinois Extension office for assistance with insect ID and insect control recommendations."

"Keeping plants healthy will help the plant to withstand insect infestations," Wolford explained. "Fertilizing, watering and weeding your vegetables will keep your plants healthy and strong, thereby helping them to ward off insect attacks."

At least every couple of days walk through the garden checking for insects. Be sure to look at the leaf surface and the underside of the leaf. Aphids are often found on the undersides of leaves and their populations can go from a handful to thousands in a few days.

"Plant flowers and herbs like sunflowers, coneflowers, dill and alyssum in the vegetable garden," he recommended. "These plants will attract beneficial insects."

Insects will hide in weeds in and around the garden. Keep the area around your vegetable garden free of weeds and after the growing season is over, remove all the weeds in the garden as these can serve as overwintering homes for insects.