Controle químico Anthonomus grandis (Boheman, 1843) (Coleoptera: Curculionidae) com base no monitoramento de botões florais de algodoeiros com brácteas abertas e/ou amarelecidas

Abstract

The cotton boll weevil, Anthonomus grandis Boheman (Coleoptera: Curculionidae), is considered the main pest of cotton in Brazil due to the several damage caused to the reproductive structures of this crop. The objective of this research was to carry out the chemical control of cotton A. grandis based on the monitoring of cotton squares with open bracts and/or yellowed. Three experiments were carried out. The first aimed to determine the period required for the opening of the bracts and the abscission of the cotton squares after the oviposition of the A. grandis females in this reproductive structure of the cotton plant. The second aimed to estimate the equivalent number of cotton squares with open bracts and/or yellowed to the number of cotton squares with oviposition punctures by the A. grandis. In the third, it was determined whether the effectiveness of chemical control of cotton A. grandis based on the sampling of cotton squares with open bracts and/or yellowed does not differ from traditional sampling based on the observation of cotton squares with oviposition punctures. The results obtained in this research made it possible to infer the following conclusions: the time for opening of the bracts and abscission of the cotton squares with oviposition punctures by A. grandis females varies according to the cotton genotype (1); the time for opening of the bracts and abscission of the cotton squares with oviposition punctures by A. grandis females, in the BRS 433 B2RF cultivar, is 4 and 8 days, respectively (2); the ratio between the number of open bracts and/or yellowed and the number of cotton squares with oviposition punctures is 2:1 (3); the A. grandis threshold control level for chemical insecticide applications based on the percentage of open bracts and/or yellowed is 5% (4) and the effectiveness of chemical control of A. grandis based on the sampling of cotton squares with open bracts and/or yellowed does not differ from that based on the observation of cotton squares with oviposition punctures by A. grandis females (5).