How to control your garden pests

Published 12:32 am Monday, July 26, 2010

Every week I receive numerous calls about controlling insects in the home vegetable garden. Despite some common thoughts there are no one or two sprays that can kill everything. In the same note, not all insects in your garden are harmful. When possible I try to offer reliable organic options, however many homeowners still prefer to use chemical sprays to get the achieved results. I have no problem with chemical sprays as long as homeowners abide by the harvest intervals and follow the labels’ instructions. So today let’s look at some common insecticides and what they control.

Q. Do insecticidal soaps really work?

Absolutely! Insecticidal soap is a formulation of potassium salts of fatty acids that control insects by disrupting cell membranes. They are not effective on all pests but work best on soft bodied insects like aphids, thrips, and mites. To have the greatest effect it is best to get complete coverage of the pests. One major advantage is they have a short pre-harvest interval and they are safe on the majority of home-grown vegetables.

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The problem with insecticidal soap comes in the form of human error. These soaps are tested and researched to ensure proper insect control and plant safety. Household soaps are not the same and can cause plant injury. The carbon chain length and other chemical factors of the soap determine whether a soap is used to kill plants, insects or germs on your hands. So please just make sure you use the proper soap for the proper job.

Q. Does Sevin kill all garden insects?

This is a popular, but untrue, thought by many gardeners. While carbaryl, the active ingredient in Sevin, is designed for homeowner vegetable insect control. It is most effective against pests with chewing mouthparts like cucumber beetles or beanleaf beetles. Sevin does not offer good control on aphids or pest with sucking mouth parts.

Q. What gets rid of aphids and tomato fruitworms?

Malathion has been somewhat a standard insecticide in home vegetable gardens for years because it can control a wide range of pests. Malathion remains one of the best products for controlling aphids. Bifenthrin is an effective pyrethroid that provides good control over stink bugs, leaffooted bugs and tomato fruitworms. However bifenthrin is limited in its use in the home garden.

Q. Are there any good organic insecticides?

Along with insecticidal soaps, there are several products like spinosad, neem oil, azadirachtin, pyrethrins and bacillus thuringiensis that have formulations acceptable for organic gardening. Spinosad is a newer microbial insecticide that works great controlling multiple caterpillar species, thrips, leaf miners and potato beetles.

Neem oil is extracted from the seed of the neem tree and is a botanical product that provides control with mites, white flies and aphids. Like insecticidal soaps thorough coverage of the target pest is required to obtain the desired control.

Pyrethrin is another botanical insecticide primarily for organic gardeners that provides quick results for many garden pests. One drawback to using pyrethrin is it has a short residual effect which means pests often come back shortly afterwards. Therefore you can add a product called PBO (piperonyl butoxide) that will help increase effectiveness. However, if you add PBO the combination is no longer acceptable for organic gardening.

This is a small list of approved insecticides for home gardening. If you would like a full list with more information please call the Adams County Extension Office.

David Carter is the director of the Adams County Extension Service. He can be reached at 601-445-8201.