Abstract
Occurrence of parasitoids in eggs of soybean lepidopteran pests, such as velvetbean caterpillar, soybean loopers and others the genus Spodoptera and Helicoverpa in Mato Grosso, Brazil was studied. Due to the scarcity of information on the natural occurrence of parasitoids in lepidopteran eggs in soybean fields in Mato Grosso surveys were conducted in Tangará da Serra to verify the occurrence these parasitoids. Surveys were conducted in two areas in Tangará da Serra, with a total of 591 eggs, of which 138 and 77 eggs were collected in area I and 274 and 102 eggs in area II, during the 2008/2009 and 2009/2010 soybean seasons, respectively. From the eggs collected in area I, 26.6% were parasitized in the first year and 30.0% in the second season. In area II, the parasitism rates were 40.2% and 27.5% for the first and second season respectively. The species of parasitoid collected was Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae) totaling 354 parasitoids. We conclude that there is a natural occurrence of T. pretiosum, this being the species of egg parasitoid found, and that parasitism rates were higher when compared with other studies under natural conditions, especially considering the large number of chemical products used in the fields. The identification of the eggs parasitoids in Mato Grosso State is important to development of biological control programs for lepidopteran pests.
Highlights
Occurrence of parasitoids in eggs of soybean lepidopteran pests, such as velvetbean caterpillar, soybean loopers and others the genus Spodoptera and Helicoverpa in Mato Grosso, Brazil was studied
From the eggs collected in area I, 26.6% were parasitized in the first year and 30.0% in the second season
We conclude that there is a natural occurrence of T. pretiosum, this being the species of egg parasitoid found, and that parasitism rates were higher when compared with other studies under natural conditions, especially considering the large number of chemical products used in the fields
Summary
Occurrence of parasitoids in eggs of soybean lepidopteran pests, such as velvetbean caterpillar, soybean loopers and others the genus Spodoptera and Helicoverpa in Mato Grosso, Brazil was studied. Among the pests that attack soybeans defoliating caterpillars, such as velvetbean caterpillar, soybean loopers and others the genus Spodoptera and Helicoverpa stand out for decreasing leaf area, and lowering the photosynthetic rate which decreases productivity, while leaving the plant susceptible to disease and sometimes causing its death In most cases these pests are controlled with wide spectrum chemicals that reduce the action of natural enemies. Due to the scarcity of information on the natural occurrence of parasitoids in lepidopteran eggs in soybean fields in Mato Grosso, surveys were conducted in two areas in Tangará da Serra with the aim to verify the occurrence of the Trichogramma parasitoids and assess the rates of parasitism. The occurrence of the phytophagous Lepidoptera was assessed, as well as the pesticides used in the study areas
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