Topical applications at submicrogram levels of the insect growth regulators (IGR) penfluron and diflubenzuron prevented the hatch of boll weevil, Anthonomus grandis Boheman, eggs. Neither compound was toxic to the weevil, however field-cage studies showed that diflubenzuron greatly reduced emergence of weevils from squares. In all field tests spray applications were initiated at first one-third grown square (<1 cm dia) and continued for 13 to 17 applications during 51 days, throughout the cotton growing season on a 3–5 day schedule. In 1981, cotton sprayed with penfluron diluted in water plus petroleum oil had significantly greater yields than cotton sprayed with penfluron only. In 1982, diflubenzuron and penfluron diluted in oil and water and applied at 0.07 kg/ha, reduced boll weevil emergence from squares 57 to 78% compared to emergence in untreated plots. In 1983, emergence of adults from bolls was reduced 39% in plots sprayed with diflubenzuron at a rate of 0.28 kg A.I./ha. In 1981, no reduction in adult emergence from bolls only was observed in plots sprayed with penfluron at rate of 0.07 kg A.I./ha; when penfluron was applied at 3 day intervals in oil boll weevil emergence from squares was significantly reduced. Yields of seed cotton were significantly greater in plots sprayed on a 3–5 day schedule with penfluron or diflubenzuron in oil, at a rate of 0.07 or 0.28 kg A.I./ha respectively, when compared to the untreated check; they were 926, 1697 to 1874, and 726 kg/ha in 1981, 1982, and 1983, respectively, In 1981 and 1982, predator populations (mostly Hemiptera and spiders) in plots sprayed with either diflubenzuron or penfluron, with or without oil, were reduced significantly compared to populations in the untreated check.
Effects of Five Insect Growth Regulators on Progeny Production, Productivity Index, Development, and Adult Emergence of the Rice Weevil, Sitophilus oryzae (L.) (Coleoptera : Curculionidae)
