CONTROLE DA LAGARTA DA SOJA (Anticarsia gemmatalis Hübner, 1818 - LEPIDOPTERA: NOCTUIDAE). IV. CONTROLE BIOLÓGICO NATURAL

ABSTRACT

The populations of the soybean caterpillar, Anticarsia gemmatalis, were evaluated by weekly assessions of the number of these caterpillars from January through March, during the soybean cropping cycles from 1982/83 to 89/90, aiming to determine the populational intensity of the insect and the efficacy of its natural control agents. The highest ocurrence of A. gemmatalis caterpillars was registered between January 30th and March 1st, when soybean plants were between growing stages R2 (full flowering) and R5 (pod grains beginning to fill). The total mortality of A. gemmatalis due to parasitoids and entomopathogens varied from 10% (83/84) to 89% (86/87). In the average and along the years there was 56% total mortality, from which 29% was due to the fungus Nomuraea rileyi (Farlow) Samson, 15% due to the parasitoid Microcharops bimaculata (Asmead), 6% due to the fungus Entomophthora sphaerosperma (Fresius), 4% due to the nuclear polyhedrosis virus Baculovirus anticarsia and 1% due to each of the parasitoids Patelloa similis (Townsed) and Euplectrus chapadae (Asmead). In four of the eight cropping seasons, there was no significant difference in grain yields for the areas with natural biological control and chemical control, thus showing the great importance of the natural biological control agents to control the caterpillars of A. gemmatalis This fact has to be carefully considered in an integrated soybean management programs aiming to rationalize or to reduce the use of agrochemicals in the crop.

RESUMO

Foram avaliadas as intensidades populacionais de lagartas de Anticarsia gemmatalis na cultura da soja, e coletadas lagartas semanalmente de janeiro a março, de 1982/83 a 89/90, com o objetivo de se conhecer a ocorrência estacionai do inseto e a eficiência dos agentes de controle natural, na região de Cruz Alta, RS. A maior abundância do inseto ocorreu entre 30 de janeiro a 1° de março, nos estádios entre floração plena (R2) e início de enchimento de grãos (R5) da cultura A mortalidade total de A. gemmatalis provocadas por parasitóides e entomopatógenos, variou de 10% (83/84) a 89% (86/87). Na média das várias safras, registrou-se 56% de mortalidade total, com 29% devido ao fungo Nomuraea rileyi (Farlow) Samson, 15% ao parasitóide Microcharops bimaculata (Asmead), 6% ao fungo Entomophthora sphaerosperma (Fresius), 4% ao vírus de poliedrose nuclear Baculovirus anticarsia e 1% a cada um dos parasitóides Patelloa similis (Townsed) e Euplectrus chapadae (Asmead). Em quatro das oito safras, verificou-se produção de grãos não significativamente diferentes para as áreas de controle biológico natural e com controle químico, mostrando a grande importância dos agentes biológicos naturais para o controle de lagartas de A. gemmatalis um fator que deve ser considerado cuidadosamente em programas de manejo integrado de pragas da soja, visando racionalizar ou reduzir o uso de agrotóxico na cultura.