Monday, May 30, 2016

Pest Spotlight: the Varied World of Aphids

Great bark aphids (Longistigma caryae) on an immature pecan
(Carya illinoensis 'Sumner').
Photo by J.S. Corser, Durham Co. Master Gardener.
Editor's note: Aphids attack most gardens and come in armies in different colors and varieties. Here is some basic information from the Clemson Cooperative Extension with links to specific aphid info by plant type. These links should help any urban gardener to first identify, then combat these pests!

General Information:
Aphids are small, soft-bodied, pear-shaped insects that measure 1/16 to 3/8 inch. There are several species of aphids. Depending on species, they can range in color from tan, pink, or green to almost black and may or may not have wings. Aphids feed on leaves and stems by piercing the plant tissue and sucking plant sap. Their feeding can cause leaves to curl or become distorted. In addition, aphids sometimes serve as vectors to transmit plant viruses which may result in disease development. The first sign of aphids being present is usually a sticky residue left on leaves. The aphids excrete a sticky substance called honeydew as they feed. The honeydew will land on any surface beneath the feeding area, such as leaves, branches, understory plants or even cars and concrete surfaces. Sooty mold is a fungus that grows on the sticky surface of the honeydew. As the sooty mold grows it will form a black, powdery or velvety coating on leaves and other areas where the honeydew landed. The good news is that sooty mold does not infect the plant tissue.

Prevention & Treatment:
Aphids have several natural enemies, such as lady beetles, lacewings, syrphid flies, damsel bugs and wasps. Since the use of insecticides will also kill beneficial insects, it is best to try to first allow the beneficial insects to reduce the aphid population. For more information on these insects, see EIIS/BB-1, Beneficial Insects and Related Arthropods (http://entweb.clemson.edu/eiis/pdfs/bb1.pdf).

If necessary, insecticidal soap (such as Safer Insecticidal Soap or Concern Insect Killing Soap) can be used to reduce the aphid population. Keep in mind that the insecticidal soap must be sprayed directly on the aphid to be effective, so be sure to coat the under and upper side of the leaves and stems. Some plants are sensitive to insecticidal soaps. For more information see, HGIC 2771, Insecticidal Soaps for Garden Pest Control.

For more information on aphids, see:

Millie Davenport
Home & Garden Information Center
http://www.clemson.edu/extension/hgic/tyk/2010/tyk04.html
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