Latent effect of microbial insecticides against the second instar larvae of the cotton leafworm, Spodoptera littoralis boisd.,

The toxic effect of larval treatment of 2. d instar of Spodoptera littoralis with the biotic insecticides alone (1. t test) or in mixtures (2. d test) was assay in the laboratory tests. The 2. d instar larvae were fed for 48h on leaves dipped for 5 seconds in the biotic insecticides alone or in mixtures of Bacillus (B) + Beauveria (Br), Bacillus (B) + Bioranza (Bz) and Beauveria (Br) + Bioranza (Bz) at the entire, half and quarter doses. Beauveria (Br) + Bioranza mixture was the most toxic one against the 2. d instar larvae, it induced 100,70 and 60% larval mortality at the entire, half and quarter doses, respectively . While, the larval treatment with Bacillus alone had the least effect, it induced l0, 10 and5% at the three tested doses, respectively. Also, the larval treatment with the biotic-products induced pupal mortality%. Bacillus (B) + Bioranza mixture had the strongest effect, it induced 35.5,15 and13.3% at the three tested doses, respectively. While, Bioranza alone gave26.7, 13.3 and11.8% pupal mortality at the three tested doses. Therefore, Beauveria (Br) + Bioranza mixture had highest effect in the total accumulative mortality percent increase, it produced 100, 80 and65% at the three tested doses, respectively. Whereas, the bacillus alone treatment had the least effect. The biological parameters of the treated larval instars were obviously affected. The larval duration was prolonged, and Beauveria + Bioranza mixture had the most potent in this respect, it increased the larval period to 29 and 27.7d at the half and quarter doses, repectively, as compared to12.2d of control. But, the larval treatment with the biocides product alone recorded the longest period of pupal duration than that of biotic-products mixtures. The pupal weight was reduced, and the larval treatment with mixtures gave the highest effect in this respect, as compared with that of biotic-products alone. While the larval treatment with these compounds reduced the pupation%, and Beauveria + Bioranza mixture had the strongest effect, it reduced the pupation to 20 and 35% at the half and quarter doses, respectively, as compared to100% of control. Also, the larval treatment with these compounds decreased the adult emergence%, and Bacillus (B) + Bioranza mixture had the greatest effect, it decreased the moth emergence to 24, 50 and 53% at the three tested doses, respectively, as compared to100% of control. While the larval feeding on these compounds increased the pupal and adult malformations %, and Bacillus+ Bioranza mixture had the highest effect exceed 23.5, 11.1, 6.7 and 76, 47, 42% for malformed pupal and adults, respectively, as compared to 0% of control. The larval treatment with biotic compounds inhibited the adult fecundity, and both Bacillus+ Bioranza and Beauveria + Bioranza mixture or Bioranza alone retarded the fecundity to reach zero%, as compared to 501 and 510 eggs/female, respectively, of control. But only the treatment with Bacillus singly decreased the eggs hatching to reach 60.9%, as compared to100% of control. The larval treatment with Beauveria + Bioranza mixture had the strongest effect in adult longevity shorten to reach 5.6d, as compared to l2d of control. Also, the sex ratio of the emerged adults was shifted in respect to control as result of the larval treatment with these products. The effect was pronounced with Beauveria +Bioranza mixture