OVERWINTERING OF A COTTON APHID PARASITE

Authors: GODFREY, KRIS - CDFA, PD/EP; McGuire, Michael

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2004
Publication Date: 3/1/2004
Citation: Godfrey, K., McGuire, M.R. 2004. Overwintering of a Cotton Aphid Parasite. Florida Entomologist. 87(1):88-91.

Interpretive Summary: The cotton aphid is an important pest of cotton and many other crops world wide. In California, high populations of aphids can reduce cotton yields and late season aphid populations can affect the quality of cotton by depositing honeydew (their sugary, liquid excrement) on exposed lint. The honeydew can cause a condition known as sticky cotton that affects ginning and milling of lint, and can affect the reputation of a cotton producing region. Natural enemies such as parasites and pathogens of cotton aphids occur in the winter months in the San Joaquin Valley of California but disappear as temperatures exceed thresholds for these naturally occurring biological controls. We attempted to enhance the natural enemy complex of cotton aphids to determine if the new natural enemies could exist in the summer and survive the winters. We introduced two species of tiny parasitic wasps (dangerous only to insects) that lay their eggs in aphids. The eggs hatch inside the aphid and the larva eats the aphid from the inside. The aphid is killed when the adult emerges. More than 74,000 of one species and 189,000 of the other were released onto six sites over a three year period. Both species were recovered through the cotton growing season but only one was recovered in the spring. These observations suggest that one of the species we introduced may have become established as a new natural enemy of the cotton aphid.

Technical Abstract: Cotton aphid, Aphis gossypii, is an important pest of cotton and many other crops world wide. In California, high populations can cause physiological reductions in cotton yield and late season aphid populations can deposit honeydew on exposed lint. The honeydew can cause a condition known as sticky cotton that affects ginning and milling of lint, and can affect the reputation of a cotton producing region. Parasites and pathogens of cotton aphids occur in the winter months in the San Joaquin Valley of California but disappear as temperatures exceed thresholds for these naturally occurring biological controls. Efforts to enhance the parasite complex have led to the release of two new parasite, Aphelinus near paramali and Aphelinus gossypii, both aphelinid parasitoids. More than 74,000 A. nr paramali and 189,000 A. gossypii were released into six cotton producing sites across three years. Recoveries of A. nr paramali and A. gossypii occurred throughout the growing season in each year but only A. nr paramali was recovered in the spring, before artificial releases were made. These data suggest that A. nr paramali may have become established as a new natural enemy of the cotton aphid.