Master Gardener: Be on the look out for those pesky aphids

Have you ever tried to enjoy the beautiful weather under your big shade tree, only to feel like it is misting on you?

Well, that mist is from aphids, which produce large amounts of a sugary liquid waste called “honeydew.” The honeydew that drops from these insects can spot the windows and finish of cars parked under infested trees.

Aphids are soft-bodied insects that use their piercing, sucking mouthparts to feed on plant sap. They usually occur in colonies on the undersides of tender new growth.

Some plants are very sensitive to feeding by certain aphid species. Saliva injected into plants by these aphids may cause leaves to pucker or to become severely distorted, even if only a few aphids are present. Also, aphids feeding on flower buds and fruit can cause malformations.

Early detection is the key to reducing aphid infestations. Make a habit of checking under leaves to look for the first invaders. For small infestations, wait a couple of weeks to see if natural predators like ladybugs, syrphid flies and lace wings show up to feast on the aphids. These small biological control bugs can clean out a lot of aphids in a hurry.

Summer oils can be used against aphids on some varieties of trees and ornamental plantings. They kill by suffocating the insects and/or disrupting their membranes.

Check the label for cautions on sensitive plants; oils can injure the foliage of some plants. Weather conditions, especially high temperatures, can increase the potential for foliage burn.

Fatty acid salts or insecticidal soaps are very good against aphids. As with summer oils, they apparently work to disrupt insect cell membranes.

They require direct contact with the insects and leave no residual effect.

Insecticides, such as malathion, Dursban (chlorpyrifos) and Orthene (acephate), are labeled for use on many shade trees and ornamental plants for aphid control. As with oils and soaps, coverage is very important, and a follow-up application may be necessary.

Be sure that the plant or crop that you are treating is listed on the product label.

Good cultural practices, such as watering and fertilization, will help to reduce plant stress created by these insects.