STINK BUGS INCIDENCE ON BT COTTON IN BRAZIL

The economic impact evaluation of the boll-feeding stink bugs complex on Bollgard ® cotton becomes necessary for the validation of the benefits from this technology in the cotton production systems in Brazil. This work studied the population of soybean migrant stink bugs species on cotton varieties (Bt and non-Bt) with the same parental, cultivated in an area bordered by a soybean crop, at the 22 o 11’ of latitude South and 54 o 56’ of longitude West, in Dourados, in the state of Mato Grosso do Sul, Brazil. The sources of variation variety (Bt and non-Bt), Nodes Above White Flower – NAWF (6-7, 5-6, 4-5, 3-4 e < 3) and interaction between variety and NAWF were tested to the numbers of nymphs, adults and total of specimens (adults + nymphs) of stink bugs species observed per shake sheet. At the end of the growing season, the cotton seed and lint yield were evaluated. Three stink bugs species occurred at the five cotton plants reproductive phases: Euschistus heros (Fabr., 1798), Edessa meditabunda (Fabr., 1794) and Nezara viridula (L., 1758). No differences to the stink bugs infestations for the sources of variation variety and interaction between variety and NAWF were detected. The most abundant species was E. heros, presenting mean number of adults per shake sheet higher since the 4-5 NAWF phase, coinciding with the full maturity phase of the soybean cultivated at the adjacencies of the experimental area. The colonization of the stink bugs species on the cotton varieties could be evidenced, due to the nymphs incidences throughout the evaluation period. Particularly, E. meditabunda seems to be the most adapted species to colonize the cotton. At the experimental conditions, the non-Bt variety presented means of seed and lint cotton yield significantly higher than the Bt variety, suggesting variation in the genetic composition of the varieties, although the Bt variety is considered essentially derived from the non-Bt.