Symptoms, Injuries, Yield Reduction and Quality Loss of Cotton Attacked by the Neotropical Brown Stink Bug Euschistus heros (F.) (Hemiptera: Pentatomidae)

The boll weevil suppression programs and the adoption of Bt cotton varieties have reduced insecticide use in several Brazilian cotton areas but they have been allowing the increase of Euschistus heros (F.) (NBSB) infestations every growing season. In recent years, NBSB has been the most important stink bug in Brazil, and it came mainly from areas cultivated with soybeans. Objectives of this study were to assess the effect of different population levels of laboratory reared E. heros adults on agronomic parameters of Bt cotton and to identify symptoms and injury on it bolls. Under greenhouse conditions, cotton plants of NuOpal^® Bollgard^® variety at the cutout stage were caged with 0, 2, 4, 6 and 8 adults of E. heros per plant for four days. The experimental design used was the completely randomized with five replications. After the infestation period, internal and external bolls injury symptoms were evaluated. At maturity, bolls were harvested and ginned to separate seed and lint. Fiber quality was measured by the HVI methodology. Data were subjected to analyses of variance (P ≤ 0.05) followed by regression analyses (P ≤ 0.10). A linear regression model showed the increase of the mean number of boll locks with internal punctures and warts with higher insect population. The mean number of boll locks with immature stained lint was higher at 4, 6 and 8 E. heros adults per plant, and fitted a quadratic regression model. Seed and lint cotton yield per plant were linearly reduced to 28 and 36% with the maximum infestation level of 8 E. heros adults per plant. The fiber micronaire and yellowness indexes were respectively reduced and increased linearly with the increase in infestation levels. This paper reports for the first time an overview of injuries and symptoms caused by E. heros on cotton.