Seasonal abundance of Plusiinae and Anticarsia gemmatalis Hubner, 1818 (Lepidoptera: Noctuidae) on soybean in Rio Grande do Sul, Brazil

Abstract

A survey of soybean Plusiinae species and their proportion in relation to Anticarsia gemmatalis Hüb., 1818, was carried out during 1986/87 and 1987/88 growing seasons in the state of Rio Grande do Sul, Brazil. The survey was carried out on soybean commercial crops at Arroio Grande, Capão do Ledo, Cruz Alta and Santa Rosa. The first infested crops by Plusiinae and A. genunatalis larvae were choosen. Field samplings were taken once a week using the ground cloth method. The Plusiinae larvae were taken to the laboratory in order to identify adults. Two Plusiinae species occurred in both years -Rachiplusia nu (Guenée 1852) and Pseudoplusia includens (Walker 1857); the first species was the most abundant. The highest population occurred in the southeast hillside and they were the first larvae to establish on soybean at Arroio Grande and Capão do Ledo. R. nu and P. includens were able to set only the first generation because of the great occurence of parasitoids and pathogens. The two species disppeared in March when A. gemmatalis had the higher population.