We received a phone call about aphids showing up in some cotton fields and thought now would be a good time to refresh everyone’s memory about cotton aphids. Cotton aphids are between 2-3 mm in length as adults. They are slow moving, and have two cornicles on the end of the abdomen also known as “tailpipes.” There are winged and non-winged aphids, but most of the time you will see the non-winged aphids. Winged adults are usually black and have two pair of transparent wings. Immatures and non-winged adults vary in color from pale yellow, bluish green, to grey black.
Immature aphids are born pregnant and can begin giving birth with in four to seven days. Therefore, aphid populations can grow very rapidly. Additionally, they can produce many generations each year.
Aphid adults and immatures have piercing-sucking mouthparts that are used to remove the sap from phloem tissue. Usually aphids are found on the undersides of leaves or feeding on terminals and other parts of the cotton plant. A heavily fed on leaf will curl downward (cup) along the edges. Aphids also secrete a sticky liquid called honeydew which will cause the leaf to be sticky and shiny. Honeydew can be problematic later in the season after bolls open because honeydew is a great food source for molds and fungus.Aphid damage to the cotton bolls.
Aphids occur in most cotton fields every year but do not usually cause economic damage. Heavy damage is more likely when the plant is already stressed do to environmental factors such as dry weather.
According to the Missouri Pest Management Guide: Seed treatments recommended for thrips offer suppression of aphids early in the season. Additionally, beneficial insects will help keep populations below threshold early season. Early season treatment is recommended when aphids are found on numerous plants and injury is apparent (leaves curled around the edges), particularly if plants are drought stressed. Midseason treatment is recommended when aphids are present in high numbers; injury is apparent; honeydew is present; and biological control agents are not reducing the aphid population. If natural enemies are present in high numbers, scout more frequently to ensure beneficials are controlling the aphids reduce aphid populations before treating. An epizootic fungus can eliminate aphid numbers nearly overnight so it is important to consider the environmental conditions before making insecticide applications