SUSCETIBILIDADE DE POPULAÇÕES DE Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) AO DIPEL EM CONDIÇÕES DE LABORATÓRIO E CAMPO

Abstract

The occurrence of larvae of the genus Helicoverpa, at population levels never before registered was verified in the region of the Brazilian cerrado in February 2012, causing losses in order of R $ 2 billion in several crops. Later identified as Helicoverpa armigera, a species never before reported in Brazil, this pest is present in all agricultural regions of the country. The objective of this research was to study the susceptibility of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) to the Dipel® bioinseticide (Bacillus thuringiensis kurstaki HD-1) under laboratory and field conditions. In the laboratory, the susceptibility of H. armigera first instar larvae from different populations (São Paulo, Minas Gerais and Goiás) and first to third instar larvae to the population of São Paulo were evaluated. The larvae mortality of the Minas Gerais population was over 80% from the first day of evaluation, being the population more susceptible among those tested. The third instar larvae of the São Paulo population were less susceptible than those of the first two instars. In the field tests, control of H. armigera with Dipel application was studied using two volumes of syrup in the soybean and sweet corn cultures. The assay was conducted in a subdivide plot, with two volumes of syrup (100 and 150 L ha-1) and the sub-plots three evaluations (24, 48 and 72 hours). The direct sowing of the two cultures and the evaluations, after application of the product were done on the same day. Leaf discs were collected at each evaluation with the objective of studying the persistence of the bioinsecticide and the mortality of H. armigera. The use of higher volume in soybean and sweet corn plants did not influence the persistence or the mortality of H. armigera. But in the sweet corn crop provides greater coverage. The persistence of Dipel bioinsecticide significantly decreases from the first to the third day after application. Studies of persistence of bioinsecticides in the laboratory and field are essential to optimize the use of this technology in the pests control of economic importance.