SEASONAL ABUNDANCE OF PLUSIINAE AND ANTICARSIA-GEMMATALIS HUBNER, 1818 (LEPIDOPTERA, NOCTUIDAE) ON SOYBEAN IN RIO-GRANDE-DO-SUL, BRAZIL

A survey of soybean Plusiinae species and their proportion in relation to Anticarsia gemmatalis Hub., 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, Capao do Leao, Cruz Alta arid Santa Rosa. The first infested crops by Plusiinae and A. gemmatalis larvae were chosen. 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 (Guenee 1852) and Pseudoplusia includens (Walker 1857) -; the first specie was the most abundant. The highest population occurred in the south-east hillside and they were the first larvae to establish on soybean at Arroio Grande and Capao do Leao. R. nu and P. includens were able to set only the first generation because of the great occurrence of parasitoids and pathogens. The two species disappeared in March when A. gemmatalis had the higher population.