EFFECT OF BACILLUS THURINGIENSIS BERLINER, A CHEMICAL INSECTICDE AND ITS MIXTURES AGAINST THE UNPARASITIZED AND PARASITIZED SPODOPTERA LITTORALIS (BOISD.) LARVAE

Document Type : Original Article

Authors

1 Department of Entomology, Faculty of Science, Cairo University, Giza, Egypt

2 Plant Protection Research Institute, Agricultural Research Centre, Dokki, Giza, Egypt

Abstract

The second instar larvae of the cotton leafworm spodoptera lit­toralis (4 days old) were fed after four days of being parasitized individ­ually by Microplitis rufiventris Kok. (=8 days old) on castor bean leaves dipped in different concentrations of Bacillus thuringiensis (delfin), the pyrethroid (baythroid) and their combinations. Data indicate that the parasitized larvae showed lower mortality rates that those of unparasi­tized ones. Consequently, the LC50 values were larger in case of parasi­tized larvae than those required for unparasitized ones at the same age. The combination of delfin and LC1 0 level of baythroid showed mortality ranged between their individual values. Data also show latent or delayed toxicity of the tested insecti­cides on the parasitoid progeny. Bioinsecticide latent effect is very low as regards cocoon formation and even adult emergence. The immature larvae of the parasitoid complete their development in B. thuringiensis infected host, if the host does not die before the maturity of the larval parasitoid inside it completed. While the latent toxicity of chemical in­secticide is more than that of the bioinsecticide, but the combination of the two insecticides ranges in between.

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