Aphid Natural Enemies and Biological Control

the spring. They have piercing-sucking mouthparts and in many cases can carry and spread plant diseases. Aphids can be small, like the green peach aphid, to quite large, like the conifer aphid. The color of the various aphid species is diverse and includes black, green, red, and yellow. They are soft-bodied with the most apparent identifying characteristic being two “tailpipes,” called cornicles, protruding from the posterior end. Gardeners and homeowners often see aphid excrement or honey dew on leaves, leaf curl with aphids hiding in the curl on fruit trees and landscape plants, or an abundance of the aphids on the underside of leaves and on plant stems. There are several naturally occurring species of predators that feed on aphids. Often the benefit of these naturally occurring predators is overlooked until predator populations are disrupted by factors such as an insecticide application or changes in the environment, like weather. In these situations, pests like aphids escape from being eaten and reproduce rapidly. Thus, it is important to scout for predatory insects and eggs amongst aphid populations and be mindful of the predator community when considering aphid control options. Although resident predator populations can maintain aphids at low levels, predators do not show up until there is a food source, so there can be a lag time between the appearance of the aphids and the appearance of predators. With aphids occurring early in the season and reproducing rapidly, it is not uncommon for them to quickly outnumber predators and their rate of feeding on aphids. Therefore, adjustments to the local environment and releases of beneficial insects may be needed to enhance their presence and effectiveness. This fact sheet lists common arthropods of Utah that eat aphids, will help identify those arthropods, and will describe management practices that aid in their success. Many of these predators will eat other plant damaging insects in addition to aphids.