Incidence of infection by Neozygites fresenii (Nowakowski) Batko in the cotton aphid, Aphis gossypii Glover was monitored biweekly during the summer of 2002 in a cotton field in Bamberg County, SC. (33°22′02″N, 81°12′14″W). Five treatments were evaluated to determine the effects of insecticides on incidence of N. fresenii: acetamiprid, dicrotophos, thiamethoxam, imidacloprid, and control. Aphids were sampled by taking 24 leaves from 12 cotton plants from each plot and placed into 30-ml screw cap vials filled with 70% ethanol. Fungus infection in aphids, numbers of aphids, percentage of winged aphids, and fungus infection in winged aphids were determined from aphids for each plot.

The highest fungus infection occurred on July 12 and 16. Acetamiprid treated plots had infection levels of N. fresenii lower than other treatments. Cotton aphid numbers in acetamiprid and thiamethoxam plots were significantly lower than in the dicrotophos treatment and untreated plots. None of the treatments caused reductions in percentage of winged aphids or in infection levels by N. fresenii in winged aphids.