Efforts to reduce insecticide usage and increase cost savings to cotton producers have resulted in millions of acres treated each year with ultra-low-volume (ULV) malathion for boll weevil control. Many researchers have reported consistently lower effective rates of ULV malathion, with 12 oz. of ULV malathion per acre being the current standard rate. A study was conducted to compare this standard treatment with a treatment of 6 oz. of ULV malathion plus 6 oz. of cottonseed oil per acre. The cottonseed oil was added to the reduced rate of malathion so that the application parameters such as application rate, nozzles used, etc. would remain constant and not confound the results of the study. The efficacy of each treatment was measured by a leaf bioassay test conducted in the laboratory and by caging boll weevils on whole plants in the field. Evaluations were done at 0 and 2 days after treatment (DAT). Results indicate that 12 oz. of ULV malathion/acre was superior to the reduced rate treatment. The one exception was the 2 DAT measurement on the first sampling date for the leaf bioassay; however, it started to rain during the collection of the samples, which may have influenced the results. The cage study, which allowed the weevils to move freely about the treated plants, had lower mortality readings than the leaf bioassay tests.