Determinação da dose de caulim eficiente contra o bicudo e seu impacto sobre a capacidade fotossintética do algodoeiro

Abstract

The cotton boll weevil is considered a major pest of fruit cotton structures in Brazil, due to severe economic losses occasioned if control measures are not adopted. This pest is widespread in all producing regions of the country, causing severe increases in the cost of production due to the applicant and abusive use of chemical insecticides. Therefore, the development of alternative technologies to the exclusive use of pesticides to control pests and diseases is one of the great challenges of sustainable agriculture and, to be adopted, such technologies should provide economic, environmental and social benefits. The objective of this research was determine the efficient dose of kaolin against the boll weevil, with more coating capacity of cotton canopy and its impact on the photosynthetic capacity of the plant. Two experiments were conducted under field conditions. The first aimed to determine the dose effective of kaolin against the cotton boll weevil and its coating capacity in different parts of the cotton plant. The experimental design was a randomized block with five treatments and four replications. Treatments consisted of spraying with kaolin suspension at doses of (1) 20 g.L -1 ; (2) 40 g.L -1 ; (3) 60 g.L e (5) 100 g.L -1 on cotton plants whenever the number of plants damaged by the weevil had 5% of punctured cotton square with oviposition. A second experiment was conducted to evaluate the physiological behavior of the cotton in response to kaolin applications under field conditions. The experimental design was a randomized block factorial 2 x 3 x 3, represented by the leaves treated with kaolin (T1 = distilled water with kaolin at a dose of 60 g/L and T2 = control, distilled water) three times of the day (H1 = 8h34min to 9h38min); H2 = 10h27min to 11h42min; H3 = 15:50 to 16:49) and three phenological stages of cotton [FF1 = flowering (01.10.14), FF2 = fruiting (10.22.14) and FF3 = production (14/11/14)]. The results obtained in this study allowed the following conclusions: (1) the most efficient kaolin doses in cotton to protect against the damage caused by the cotton boll weevil are the 60 g.L -1 -1 , 80 g.L ; (2) the best value for money is obtained in the cotton spraying with kaolin at a dose of 60 g.L and (3) the kaolin reduces leaf cotton photosynthesis, but this photosynthetic loss is offset by the reduction of canopy temperature.