Padrão de ocorrência de espécies de insetos associados à cultura da aveia-branca Avena sativa (L.) em Dourados visando a produção de forragem ou palhada para plantio direto

Abstract

Oat has been established as one of the main winter crops in southern Mato Grosso do Sul. Oat may also be an alternative for forage production. Additionally, it produces grain that might be used as human and animal food source, and as plant residues to produce a surface cover for the soil in no-till farming system. The aim of this work was to do a survey of the entomofauna in oat crop in Dourados-MS, in the crop of 2014. The experiment was conducted at the Experimental Farm of Federal University of Grande Dourados (FAECA in Portuguese) in Dourados – State of Mato Grosso do Sul in a 4 ha area. This area was divided into 80 experimental unities with 169 m2 each. Experimental assessments were conducted weekly by using a stainless steel quadrat with 0.25 m2 and only data inside the quadrat were assessed. An amount of 10 assessments were done until the end of the experiment. For aphids data were collected from ten plants inside the quadrat, whereas for other species data were collected from all the plants inside the quadrat. The main type of insects found were the aphid Rhopalosiphum padi, dipteran insects from the family Syrphidae and the fall armyworm (Spodoptera frugiperda). The aphid R. padi showed the largest population density, with a peak being reached during the fifth assessment (38 days after plant emergence). It was also observed the largest amount of dipterans from the insect family Syrphidae during the fifth assessment. From this assessment onwards it was possible to verify these insects (Syrphidae family) preying on R. padi, as a result, controlling the aphid. The fall armyworm S. frugiperda showed the largest population density at the beginning of the experiment. However, its population decreased all over the experiment due to weather conditions and the effect of the entomopathogenic fungus Nomuraea rileyi. In this experiment it was possible to identify that R. padi is one the main pests of oat crops. However, in parallel, a satisfactory natural control occurred by the insect family Syrphidae. Consequently, no management with insecticides was required during the crop season of the present study.