Eficácia do tratamento de sementes e tecnologia Bt contra Spodoptera frugiperda em estádios iniciais do milho

Abstract

The objective of this study was to evaluate the efficacy of the seed treatment insecticides Chlorantraniliprole plus Clothianidin against Imidacloprid+Thiodicarb on early corn growth stages. Seeds treated with the fungicide Carbendazim+Thiram were used as a positive control (check). Formulations were diluted in potable water for uniform pesticide per seed amount application ratio (14mL kg-1 of seeds or 22mL kg-1 of seeds for the seed treatment containing Imidacloprid+Thiodicarb). The seeds were treated in a Wintersteiger liquid seed treater Hege 11 right before sowing and only one seed was sown per hole for avoiding over active ingredients soil concentration. No plant thinning was needed and each plot had nine plants. Neonate and 3rd instar caterpillars reared at the Brasília insectary were used for the artificial infestation. Ten neonate caterpillars were infested with corn cob grits in bazookas and only one 3rd instar caterpillar was infested with paint brushes per plant. The artificial infestation was finished in only one day. The hybrids 30F53 and 30F53YH (Optimum™ Intrasect™ Cry1F/PAT x Cry1Ab) were sown in five different sowing dates (seven days interval) and the artificial infestation was accomplished 42, 35, 28, 21 and 14 days after sowing (DAS). Scoring was accomplished seven and fourteen days after artificial infestation (DAI). The experiment was sown at the “Santa Maria de Baixo” farm in Itumbiara – Goiás – Brazil. The data was analyzed with the Tukey Test for the control efficiency in accordance with what is described in the Davis scale. For the non-GMO hybrid, V2 infestation with neonate caterpillars, the Imidacloprid+Thiodicarb and Chlorantraniliprole plus Clothianidin efficacy were similar and all treatments were better than the check. The treatments with Chlorantraniliprole plus Clothianidin provided the best control for 3rd instar remaining caterpillars when compared to Imidacloprid+Thiodicarb, which did not differ from check 7DAI. 14DAI Imidacloprid+Thiodicarb was superior to the check and inferior to Chlorantraniliprole plus Clothianidin. For the GMO hybrid, V2 infestation, Chlorantraniliprole plus Clothianidin behaved the same as Imidacloprid+Thiodicarb to control neonate and remaining 3rd instar caterpillars and all treatments were better than the check 7DAI. There was no difference between the check and the other treatments 14DAI.