March 21, 2008

The return of gardening season also signals the return of insect pests that prey upon vegetables. University of Kentucky Entomologist Ric Bessin said home gardeners have many options to effectively manage these pests during the growing season.

Many insects become active when the average daily temperature reaches 45 degrees or so. They tend to emerge first in the southwest part of the state and move northeast, reaching the northern most counties seven to 14 days after first emergence.

“I think when many people think of insect control, they think of insecticides first, and I don’t think that should always be the case,” he said. “I think there are many situations where the home owner has additional options.”

The best pest management options for gardeners vary, depending on the types of vegetables a person grows. One of the simplest, low cost forms of pest control that small home gardeners can do involves people going out to their gardens in early morning with a bucket containing soapy water. Bessin said this is the time of the day when many of the insects are sluggish and have slow reaction times. Therefore, gardeners have the opportunity to easily knock the insects off the plants and drop them into the bucket. The soapy water kills the insects almost immediately.

Fortunately, some gardeners may not have as bad of a pest problem this year due to the state having more of a normal winter with consistently cold weather and some snow. Bessin said the prolonged cold periods possibly could reduce the numbers of some insects, such as flea beetles, that overwinter on top of the soil in debris. Corn earworm, an insect that overwinters in the soil, could be pushed farther south due to the cold temperatures.

However, the cold weather will not phase out all of the insect pests. Some of the most common pests home gardeners annually face include the Colorado potato beetle and tomato hornworm. Preventive control options for annual pests include looking for pest resistant varieties, selecting a planting date when pests are not as common, tilling the soil and crop rotation, he said.

“It pays to put money into preventive controls when we’re certain that pests are going to show up,” he said.

Gardeners can reduce their chances of becoming infested with the Colorado potato beetle by applying a 6-inch layer of straw on top of potatoes after they have been planted. The straw layer also makes it easier for gardeners to dig up the potatoes at the end of the season, Bessin said.

While some insects are pests, some can be very beneficial to gardeners; including a type of wasp that kills the tomato hornworm. The wasp inserts its eggs into the insects like the tomato hornworm and eventually takes over the insect’s entire body. The wasps do not harm vegetables. White, egg-like cocoons may appear on the tomato hornworm’s body after it has been killed by the wasps. Bessin said gardeners should leave the tomato hornworm alone if they see this on one of their tomato plants because it is a signal the worm is dead and no longer a threat to the plant.

“We often don’t appreciate the levels of natural control that we have,” Bessin said. “If we didn’t have any beneficial insects, we would see pest problems of epic proportions.”

For more pest control options, visit the UK Entomology Department’s ENTfacts Web site or contact your county’s Cooperative Extension Service.