Danos de Diatraea saccharalis (Fabr., 1794) em arroz irrigado na fronteira oeste do Rio Grande do Sul

Abstract

The objective of this work is to verify the efficiency of the sampling methods, incidence and proportions of damages, as well as the population fluctuation of the stem drill (Diatraea saccharalis) in the region of the West Frontier of Rio Grande do Sul. Commercial culture located in the municipality of Itaqui-RS in the 2016/2017 harvest. Two sampling methods were evaluated, being they visual and through the network of sweep. A visual sampling was performed observing each point for 5 and 10 minutes in the vegetative and reproductive phases, respectively. A sampling by scanning network was performed through 10 traces with entomological network in linear direction as taipas. After the ripening of the grains with samples of collectors at each point, where the stems were separated in the laboratory in attacks and not attacked, allowing an extraction of the variables. Through the number of insects observed, a field without sampling of daughters was determined the population fluctuation. The data were submitted to simple linear correlation analysis using Microsoft Excel 2016. They were not captured with the scanning network. Sampling was added to adult observation and one field proved to be important for the determination of infestation and estimated losses caused by the pest. Significant correlations were found between the average weight of the panicles and the total number of species, the percentage of empty spikelets and the reduction of yield. These correlations indicated that the increase in the population of the pest caused infertility of the panicles, reducing the average weight of the nets and, consequently, a reduction of the productivity of the crop. The attack of D. saccharalis has been found to occur from stage V3 of the culture that persists until the time of harvest. Two popular peaks of the species were observed at 70, 105 and 120 days after sowing.