Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/6/1997
Publication Date: N/A
Citation: N/A Interpretive Summary: Insecticides can have a negative impact on natural enemy populations and thus contribute to outbreaks of secondary pests. Since malathion, fipronil, and cyfluthrin are insecticides which may be used by the Boll Weevil Eradication Program to control boll weevils, we conducted tests to determine the toxicity of these insecticides to two natural enemies commonly found in cotton. The two natural enemies were the big-eyed bug, a predator of many worm species, and Cardiochiles nigriceps, a parasite of the tobacco budworm. Our tests showed that overall malathion was the most toxic. The two natural enemies were less susceptible than the boll weevil to fipronil residues 24 and 48 hours after the cotton leaves were sprayed with insecticides. They were also less susceptible than the boll weevil to cyfluthrin residues immediately after the leaves were treated.
Technical Abstract: The tolerance of two natural enemies, Geocoris punticeps (Say), the big-eyed bug which is a general predator of several lepidoptera species, and Cardiochiles nigriceps Vierick, a host-specific parasitoid of the tobacco budworm, to residues of malathion, fipronil, and cyfluthrin applied ultra low volume (ULV) was determined for 0, 24, and 48 HAT (hours after treatment). Toxicity to the target pest, Anthonomus grandis Boheman, the boll weevil, also was evaluated. Exposure to malathion residues at 0 HAT resulted in highest mortality for the three insects. Cyfluthrin was less toxic than malathion at 0 HAT for all insects. Toxicity of malathion residues decreased sharply at 48 HAT for all three insect species. Toxicity of fipronil remained the same for the boll weevil from 0 to 24 HAT, but was lower for the two natural enemies at 24 HAT compared to 0 HAT. Also, fipronil was less toxic to C. nigriceps than to big-eyed bugs at 24 HAT. Fipronil was the only insecticide which resulted in mortality for the boll weevil at 48 HAT. Toxicity to the boll weevil was much lower with cyfluthrin than malathion and fipronil at 24 HAT. However, cyfluthrin was more toxic to the two natural enemies than to the boll weevil at 24 HAT.