CHAD GULLEY, Texas A&M AgriLife Extension Service
Have you noticed small particles resembling cotton or white lint floating like snowflakes in the air around your landscape? These are wooly aphids. Winged adults take flight, making it appear that a small tuft of cotton has grown wings.
There are more than 250 species of aphids that feed on agricultural and horticultural crops. Several cause damage in Texas. A number of ornamental plants, trees and shrubs can be hosts to these pest species.
Aphids are small insects, ranging from 1/16 to 1/8 inch in length. Most aphids reach sexual maturity in four to 10 days, and the reproductive period is about three weeks under good environmental conditions. The average lifespan of an adult is about one month. Despite their relatively short lifespans, aphids can be quite prolific. In fact, aphids can reproduce faster than any other insect.
Many species of aphids exist and they mainly affect ornamentals. High populations of some species build up during winter months on evergreens or bedding plants, and populations build up rapidly on new growth in the spring. Some species, such as wooly aphids, are favored by hot dry weather.
Common wooly aphids include the Asian Hackberry Wooly Aphid and the Wooly Oak Aphid.
Aphids draw sap from plant tissue (phloem) using mouthparts adapted for piercing and sucking. Some aphids feed on foliage, while others feed on the twigs, limbs, branches, fruits, flowers or roots of plants. If left unchecked, aphids can stunt plant growth, deform and discolor leaves and fruit or cause galls to form on leaves, stems and roots.
Wooly aphid damage is aesthetic and rarely impacts the overall health of larger, established trees. In most cases, natural biological controls, such as lacewings, lady beetles, hover flies and parasitic wasps, keep wooly aphid populations below numbers that can damage trees, despite the appearance of distorted leaves.
Aphids suck plant sap from leaves, stems or even roots of plants. Most are very host-specific, meaning they feed on only one or a few related kinds of plants. Therefore, there is usually little danger they will move to other, different kinds of plants.
If wilting is apparent, or the sticky honeydew (aphid droppings, may result in plant covered with black sooty mold) becomes a problem, control with insecticides labeled for aphid control. Otherwise, leave them alone and watch nature take its course with predators and parasitoids coming in to feast on these pests.
Among the choices for control, insecticidal soaps and horticultural oils are good, low-impact options for these insects. Be sure to spray leaf undersides and contact the aphids directly, for these sprays only kill on contact. Product containing imidacloprid can be an effective aphid control, but it may take a month for results to become apparent.
As with all applications of insect or pest control, read and follow all label directions. An integrated pest management approach is the best options in most cases for control of pest species. An IPM approach incorporates a number of proven techniques including biological control, mechanical control, cultural control and chemical control where warranted, using the least toxic controls as a last resort. IPM may include a number of these control options to mitigate pest damage.