Evergreens and Aphids

Description

• Aphids are very small pests, rarely exceeding 1/8 inch at maturity. The soft-bodied, oval insects come in a range of colors, including yellow, red, black, green or orange. The pair of pipelike cornicles growing from the rear of the body distinguishes aphids from other sap feeders. Certain aphids are coated with waxlike or woolly material and may be winged or wingless. The majority of aphids are females. The males only occur for a brief period during late summer.

Life Cycle

• All plant aphids, including those found on evergreens have a rapid growth rate, going from their newborn stage to adulthood in about 10 to 14 days. Each adult female produces three to five young every day throughout her lifetime of about a month. Unless controlled quickly, aphids can multiply dramatically. It takes less than a dozen aphids to produce nearly thousands of aphids on the host plant in a couple of weeks.

Damage

• The pests commonly congregate in large numbers on the undersides of foliage to feed on sap. As their population grows, they also spread to stems and buds. The loss of sap leads to discolored, yellowed and distorted foliage. Tree shoots are stunted and growth is also like to be distorted from the effect of toxins that some aphid species inject in trees. Certain aphids cause gall formation on trees. Aphids excrete sticky honeydew that promotes the growth of sooty black mold on infested tree areas. This reduces the aesthetic value and invites secondary pests like ants into trees.

Management

• Control the presence of ants in aphid-infested evergreens as they protect aphids from their natural predators. The introduction of natural predators into trees provides an effective biological control of the pests. Natural aphid enemies include various types of parasitic wasps, lacewings, syrphid flies and lady beetles. The use of insecticide is recommended when 5 percent or more of foliage tips display aphid colonies, according to the University of Kentucky Extension. Effective insecticides include carbaryl, acephate or malathion.