Ocorrência, distribuição espacial e métodos de controle de Melanagromyza sojae, em soja

Abstract

The study aimed to confirm the presence of M. sojae in soybean crops in Paraguay, to characterize the distribution of soybean stem fly in soybean field and to evaluate management strategies to control M. sojae. The dissertation consists of three articles. Article 1 is the first record of M. sojae in Paraguay, for the study specimens soybean stem fly were collected in four localities of Paraguay and later submitted to molecular techniques of extraction, purification, amplification and DNA sequencing. Article 2 studied the spatial distribution of M. sojae and its injuries in soybean crop. The study was carried on a 45 hectares soybean field in the municipality of Santa Rosa de Monday, using a regular sampling grid of 70 x 70 meters of size and 92 sampling points. Analysis of the spatial distribution was performed by semivariograms and maps were generated by ordinary kriging with ArcGIS computational program. Article 3 consists on the evaluation of insecticides and methods of application to M. sojae management and is separated in tow experiments performed in San Cristobal. In experiment 1 were evaluated the effect of insecticides applied at sowing as seed treatment or in the sowing furrow and the combination with foliar applications at 18 and 28 days after emergence - DAE. The aim of the experiment 2 was to evaluate the effect of insecticides applied in the early of soybean development stage, at 10 and 22 DAE with aerial spraying only, to control M. sojae. The species of soybean stem fly occurring in Paraguay crops is M. sojae. The comparison of the COI region of mtDNA with the sequence deposited in Gene Bank confirms the occurrence of M. sojae in Paraguay. The spatial distribution pattern of specimens and its damages in soybean crops occurs in an aggregate way, however, plant development patterns is random and not associated to M. sojae occurrence. Insecticides applied as seed dressing, in sowing row and aerial application at the crop initial development stages controls M. sojae and its injuries in early plant development.