ABSTRACT
The boll weevil Anthonomus grandis (Boheman 1843) (Coleoptera: Curculionidae) is the most important cotton pest in Brazil, and insecticides play an important role in controlling its adults, so the development of products with new modes of action is essential to achieve successful control alternatives and resistance management options. The objective of this study was to evaluate the efficacy of some neonicotinoid insecticides to control the pest. The experimental design consisted of completely randomized blocks, with nine treatments and four replications. The following treatments (dosage of the commercial product per hectare) were applied in the field (with 9.8% of damaged squares at the beginning of the study): 1) Imidacloprid 200 SC (525 mL); 2) Imidacloprid 200 SC (700 mL); 3) Imidacloprid 200 SC (1,050 mL); 4) Thiamethoxam 250 WG (300 g); 5) Acetamiprid 200 SP (300 g); 6) Clothianidin 600 SC (262,5 mL); 7) Thiacloprid 480 SC (300 mL); 8) Endosulfan 350 CE (2,000 mL); and 9) Untreated control. The efficacy of insecticides was calculated with the Abbott formula; the data of damaged squares in each treatment was submitted to variance analysis and its means compared by Tukey test (? = 0.05). The results showed that Clothianidin 600 SC (262.5 mL/ha) was the most efficient neonicotinoid and reached 73% of efficacy at 6 days after the third application. The cyclodiene Endosulfan 350 CE (2,000 mL/ha), which was the standard farmer treatment, did not control the boll weevil as frequently cited. There were no significant differences in cotton production (fiber plus seed and bolls per plant) among treatments.
KEY WORDS
Resistance; chemical control; efficacy