Influence of weather on efficacy of pyrethroid insecticides for boll weevil (Coleoptera: Curculionidae) and bollworm (Lepidoptera: Noctuidae) in cotton
1989
Guillebeau, L.P. | All, J.N. | Javid, A.M.
During 1984-1987, variable seasonal weather patterns offered an opportunity to evalutate the influence of rainfall and sunlight on pyrethroid treatments applied on a 7-d schedule for control of boll weevil, Anthonomus grandis grandis (Boheman), and bollworm, Heliothis spp., damage. Conditions ranged from drought (with daily highs above 35 degrees C) to frequent rain during the 4-yr period. All of the pyrethroids tested maintained high levels of bollworm control through all weather patterns with no significant differences. Highest overall efficacy for boll weevil occurred in 1984, which was intermediate among the four seasons in terms of rainfall and sunlight received. In 1985 and 1987, rain frequently fell within 2 d after insecticide application; efficacy and consistency of all treatments for boll weevils were reduced compared with 1984 or 1986, but relative efficacy rankings did not change. Rain just after insecticide treatments in 1984 and 1986 also corresponded with reduced efficacy. Rain falling more than 2 d after spraying had no apparent effect on efficacy. In 1986, the efficacy of flucythrinate (0.028 kg [AI]/ha) and tralomethrin (0.0168 kg [AI]/ha) for boll weevil declined rapidly during a 3-wk period with clear skies and a mean daily high temperature above 37 degrees C and rebounded as daily high temperatures moderated. Control of boll weevil damage by cypermethrin (0.0672 kg [AI]/ha), esfenvalerate (0.0336 kg [AI]/ha to 0.040 kg [AI]/ha) and cyhalothrin (0.028 kg [AI]/ha to 0.0392 kg [AI]/ha gradually decreased during this hot period and rose again as temperatures abated. Cyfluthrin (0.028 kg [AI]/ha) maintained 85% control of boll weevil damage throughout the hot interval.
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