Efeito da desfolha na cultura da soja na microrregião de Paragominas, Estado do Pará.

Abstract

The defoliation caused by insects stands out as one of the main limiting factors of soybean yield. The damage caused by pests varies from one place of cultivation to another, according to characteristics of climate, variety, management, depending on the species and population density of the insect. The application of insecticides in the soybean crop, based on pre-scheduled packages and protocols, has reduced the population of natural enemies, increased resistance of insect pests and the contamination of man and the environment, as well as raising production costs. Integrated Pest Management (IPM) proposes actions that reduce the need for the use of chemical inputs, among them, the use of the Economic Damage Levei (EDL) and the Levei of Action (LA) that can help the apply the insecticide at the appropriate time. However, NDE and NA for soybean defoliation and defoliants were defined based on studies carried out by EMBRAPA, in the states of Paraná, Mato Grosso and Goiás, which have different soil and climatic characteristics than those of the State of Pará. The objective of this work was to determine the levei of economic damage to defoliation of soybean in the field conditions of the municipality of Paragominas-PA. The research was developed in the Juparanã company arca, on the farm called Progresso. The cultivar M 8644 IPRO was used with four leveis of artificial defoliation: 0, 17, 33 and 67% in the phenological stages V8, R2 and R5. The experimental design was a randomized block design in the 4x3 factorial scheme with four replications. We evaluated the Leaf Arca Index (LAI), growth, number of nodes, branches, productivity and productivity components. Data were submitted to analysis of variance, Tukey regression and / or test at 5% significance were done through SAS University Edition software. The regression analysis of productivity as a function of the leveis of defoliation showed an adjustment for the second degree equation for the R2 and R5 stages, demonstrating that in the R2 stage, maximum productivity would be reached with the defoliation levei of 26.4% with the LAI of 3.33. At the R5 stage, maximum productivity would be achieved with the defoliation levei of 8.17%, corresponding to an LAI value of 3.69.