Influence of Insecticide Application Timing on Damage by Smicronyx fulvus and S. sordidus (Coleoptera: Curculionidae)

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Abstract
Permethrin (0.11 and 0.056 kg [AI]/ha), cypermethrin (0.056 kg [AI]/ha), and carbofuran 4F (0.56 kg [AI]/ha) were compared with an untreated check for the control of Smicronyx fulvus and S. sordidus infestations in sunflower, Helianthus annuus L. over a period of 3 years. Insecticides were applied by a ground sprayer to individual plots when 10 and 80% of the plants were in bloom. Pyrethroid treatments reduced the amount of seed infested by weevils from 26.6 to 71.4% when compared with the untreated check. Time of application did not greatly affect performance of the pyrethroids in 2 of the 3 years. However, late treatments offered better control in 1983, and carbofuran applied at early bloom provided better control than treatments applied later in 2 out of 3 years. Adult emergence comparisons between S. fulvus and S. sordidus indicated earlier emergence and an increasing population of S. sordidus.

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