Aphids are no small problem

Published on Saturday, 17 May 2014 23:11 - Written by Chad Gulley Extension Agent

Aphids are small insects that feed on agricultural and horticultural crops. Aphid infestations can build to severe levels rapidly as these insects tend to reproduce very quickly. With garden and landscape plants, scout regularly to prevent heavy infestations of aphids.

There are more than 250 species of aphids or what some call “plant lice.” Aphids range in size from 1/16 to 1/8 of an inch in length. Aphids are soft-bodied and vary in color and shape. Their bodies appear to be pear-shaped, globular, oval, spindle-shaped, or elongate. Aphids range in color from black, grey, red, orange, yellow, green, brown, or blue-green to name a few. Aphids of a single species may have several color and shape patterns.

Aphids may or may not have wings. The body of the aphid is segmented and the head is distinct from the thorax and abdomen. The head of the aphid bears a pair of segmented antennae and mouthparts for sucking plant juices. Toward the end of the abdomen is a pair of tube-like structures called “cornicles” and can be found on most species. These structures secrete a defensive fluid.

Most aphids reproduce and develop through simple metamorphosis. Most aphid species can reach maturity in four to ten days. The reproductive period for aphids is about three weeks. The average life span of an adult aphid is about one month. Aphids can reproduce faster than any other insect species and are very prolific.

Aphids draw sap from the plant tissue using their piercing or sucking mouthparts. If left unchecked, aphids can stunt plant growth and can deform and discolor leaves and fruit of some plants. Many aphids secrete a sticky substance called “honeydew” which is similar to sugar water. This sticky substance falls on the leaves and other objects below an infestation. Then, a fungus called “sooty mold” can form; this causes a black coating. This coating prevents sunlight from reaching the leaf surface restricting photosynthesis.

Aphids can be found anywhere on the plant but are typically found on the underside of the leaves. It is important to monitor your plants once or twice a week for aphid populations.

Common aphid species in Texas include the cotton or melon aphid, green peach aphid, crape myrtle aphid, and the oleander aphid. Control of aphids includes biological, mechanical, and even using least toxic chemical controls.

Biological controls include other insect species like lady beetles, lacewings and a number of parasitic wasp species. Mechanical controls include dislodging the aphids by spraying the host plants with water at high pressure. This works well for house plants or small plantings. It also may be necessary to plant certain non-host or resistant plant cultivars or varieties.

Least toxic chemical controls include insect growth regulators, microbial insecticides and insecticidal soaps. These products control aphids yet have the least impact on natural enemies of aphids. Insect growth regulator products do not kill the fully developed adult aphid, but it works to prevent the insects’ development and is most effective when the population first appears. Insecticidal soaps trap and suffocate the aphid and damage the waxy layer of their exoskeletons causing their bodies to dry out.

As with any pests of your crops, proper identification is important. Control measures will vary and if using chemical controls, be sure to read and follow all label directions. Monitor the plants for aphid infestations, develop a plan of action to control the insect species, and look for signs of any plant disease outbreak that may arise.

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