Some Biological Effects of a Bacillus thuringiensis Product on the Gypsy Moth Larvae

Abstract

Insecticidal and antifeeding activities of a Bacillus thuringiensis product "Thuricide A" against the 3rd-to 6th-instar larvae of the gypsy moth, Porthetria dispar, were investigated under a laboratory condition. During the first several days following the ingestion of wild rose leaves treated with Thuricide A, the larvae showed a remarkable decreased appetite but the mortality was low. The mortality was gradually increased after 3 days until the 8th day after the ingestion of Thuricide A. The decreased appetite in feeding was observed from the 1st day, and did not recover so long as treated leaves were given successively. When treated leaves were changed with untreated ones on the 3rd day the recovery in larval appetite was observed. It could be considered that the antifeeding effect of Thuricide A is temporary. When the treated and untreated leaves were placed in the same cage and the larvae were placed on untreated leaves, almost all larvae did not move to the treated leaves. When larvae were placed on the treated leaves, however, they crawled about actively until some larvae reached untreated ones.

Estudos Sobre os efeitos de um produto a base de Bacillus Thuringiensis var. Kurstaki em Ephestia Kuehniella (Zeller, 1879) (Lepidoptera: Pyralidade) e no seu Ectoparasitoide Bracon hebetor (Say, 1836) (Hymenoptera: Braconidae)

“…Tais efeitos adicionais devem ser investigados, já que podem incrementar os níveis de controle populacional. Além deste fato, mudanças comportamentais podem ser desencadeadas devido a repelência ou deterrência a componentes presentes na formulação de alguns produtos, o que pode ocasionar alteração em parâmetros biológicos, como desenvolvimento, longevidade e capacidade reprodutiva (ASANO, 1973;RAMACHANDRAN et al, 1993;GEBEL & THIERY, 1994).…”

“…É possível que esta diminuição na viabilidade, bastante evidente na concentração de 4,82%, se deva ao fato do produto à base de Bacillus thuringiensis var. kurstaki poder provocar inibição alimentar e o abandono do alimento em decorrência da bacteriose ou de algum componente do produto formulado (ASANO et al, 1973;GOULD et al, 1991;HABIB & ANDRADE, 1998). Pode-se supor que as larvas, sobreviventes ao tratamento com a farinha contaminada, empupariam como mecanismo de escape à exposição ao patógeno, procurando garantir sua sobrevivência.…”