DETERMINAÇÃO DO NÍVEL DE DANO ECONÔMICO DE SPODOPTERA FRUGIPERDA (SMITH, 1797) (LEPIDOPTERA: NOCTUIDAE) EM CULTIVARES DE ALGODÃO CONVENCIONAL E BT

Abstract

The increase in the occurrence of S. frugiperda to the cotton crop in Brazil has been growing since Bt cultivars do not present satisfactory control over the pest. The determination of the levels of economic damage for cotton as well as for Bt cultivars are not yet available for the elaboration of control strategies, which are of fundamental importance to measure the potential of damage in the crop. In order to determine the level of economic damage in cotton cultivation, especially in cultivars that express Bt proteins, studies were conducted under field conditions in the city of Primavera do Leste, where five levels of infestation were used: 0, 1, 2, 4 and 8 m-1 caterpillars of Spodoptera frugiperda, at 60 and 100 Days After Emergency (DAE). The productivity data obtained in the two times evaluated showed a linear reduction as there was an increase in S. frugiperda infestation. There was a linear increase in damage with the increase in infestation, but it is observed that the difference in the number of damaged structures between the control treatment and the infestation of a S. frugiperda m-1 does not obey the same proportion for infestations of 2, 4 and 8 m-1 caterpillars. The level of economic damage for Widestrike® technology is 12.48% infestation at 60 DAE and 11.19% at 100 DAE, these levels are very close to that found for the conventional (non-Bt) cultivar that presented a level of damage of 11.31 and 9.25% of infestation at 60 and 100 DAE respectively. The TwinLink® and Bollgard II® technologies showed very similar levels of economic damage for the two periods evaluated, where the TwinLink® technology obtained 17.16 and 17.35% of infestation and the Bollgard II® technology presented 17.27 and 17.19% infestation at 60 and 100 DAE respectively. It was not possible to determine the economic damage levels for the TwinLink Plus® and Widestrike 3® technologies.