Stay alert for pests of winter vegetable crops
STARKVILLE, Miss. -- Spring and summer bring out the insects in Mississippi lawns and gardens, but fall has its own share of pests that attack cool-season vegetables.
Blake Layton, an entomologist with the Mississippi State University Extension Service, said common pests of fall vegetable crops do well in cool weather and specialize in feeding on brassica crops, which also prefer cooler weather. Uncontrolled infestations can cause serious leaf damage to cool-season vegetable crops.
“Many of the vegetables grown in late fall and winter gardens are brassica crops -- crops like broccoli, cabbage, bok choy, turnips, mustard, collards and other ‘Asian greens,’” Layton said. “The pests that attack these crops are different from what we see in our summer gardens.”
Pests of these fall and winter vegetables include armyworms and a rather large group of caterpillar pests such as cabbage loopers, diamondback moths, cross-striped cabbage worms and imported cabbage worms.
“There are also some important beetle pests,” Layton said. “Flea beetles are quite small, but heavy infestations cause damage because the insects chew tiny holes in the leaves and can seriously damage young plants.”
Yellow-margined leaf beetle and vegetable weevil are two beetles that specialize in feeding on winter brassicas. They often occur together. Although these pests are not small, Layton said they are easy to overlook.
“Gardeners are often puzzled when they experience heavy damage to crops like bok choy, turnips or mustard,” he said. “To find these beetles, you have to get down on your hands and knees and carefully check the bases of the plants.”
Layton said these two nonnative insects have been established in the Southeast for many decades and occur throughout the state. Both are capable of causing severe defoliation. Failure to detect and treat these pests early can result in unmarketable crops.
While all of these pests can cause big damage, they are relatively easy to control with timely, well directed insecticide sprays, Layton said. Be sure to choose the proper insecticide, apply it at the proper rate, and observe the preharvest interval specified on the label.
Rick Snyder, MSU Extension vegetable specialist working from the Truck Crops Branch Experiment Station in Crystal Springs, said it is important to identify which insect or insects are causing the problem before reaching for an insecticide.
“Some insecticides are designed for chewing insects, while others work better on piercing-sucking insects,” Snyder said.
To prevent problems from flaring up, check vegetable plants daily to notice holes in the leaves or other damage as soon as it occurs.
“Control is much more effective when it starts early before insect populations blow up into large numbers,” Snyder said. “Follow the label directions on the insecticide, and don’t be afraid to handpick larger insects like hornworms and other caterpillars. You can safely remove and destroy them without any sprays at all.”
Publications offered online can help with insect control. See P2347, “Insect Pests of the Home Vegetable Garden,” and P1091, “Garden Tabloid,” at http://extension.msstate.edu/publications.