Assessments the toxic effects of entomopathogenic bacterium, Bacillus thuringeinsis subsp. kurstaki, and methomyl insecticide on larval instars of the greater sugarcane borer; Sesamia cretica (Lederer)

Abstract

This study was conducted to evaluate the efficacy of the bio-insecticide Bacillus thuringiensis (Dipel 2x ® 6.4 % WP) against, 1 st and 2 nd instar Larvae of Sesamia cretica compared with methomyl (Lannate 90 % SP). After 48 hours from treatment, The LC50 value of B. thuringiensis for 1 st instar and 2 nd larvae were 0.00526 and 0.7 gm, respectively. While the LC50 of methomyl after 24h. for 1 st instar and 2 nd larvae were 3394 and 5481 ppm, respectively. After treatment of 1 st and 2 nd instars larvae of S. cretica with LC50 concentrates of B. thuringiensis, the average larval duration of S. cretica were (36.53 & 24.69) and (33.78& 20.31) days for treated and untreated, respectively. In addition, the pupation percentage was (47 & 92 %) and (18 & 84 %) for treated and untreated, respectively. The larval mortality percentage was (53 & 8 %) and (82 & 16 %) for treated and untreated, respectively. The pupal weight for (treated & untreated), S. cretica were (0.1887 & 0.184 gm) and (0.1842 & 0.1601 gm) when it treated as 1 st and 2 nd instars larvae, respectively. Furthermore, the pupal duration were (12.14 & 10) and (10.44 & 9.83 days) for (treated & untreated), when S. cretica treated as 1 st and 2 nd instar larvae, respectively. The total adult emergence for 1 st instar and 2 nd instar larvae were (94 & 100%) and (100 & 100%) for treated and untreated, respectively. On the other hand results indicated that, after treatment of 1 st and 2 nd instar larvae of S. cretica with LC50 concentrates of methomyl, the average larval duration of S. cretica were (31.41 & 24.69) and (33.87& 20.31) days for treated and control, respectively. The pupation percentage was (34 & 92 %) and (28& 84 %) for treated and untreated when S. cretica treated as 1 st and 2 nd instars larvae, respectively. The larval mortality percentages were (66 & 8 %) and (72 & 16 %) for treated & untreated, respectively. The pupal weight for treated and control, were (0.1626 & 0.184 gm) and (0.1994 & 0.1601 gm), respectively. The pupal duration were (12.41 & 10) and (10.83 & 9.83) days for treated and untreated, respectively. The total emergence percentage for 1 st instar larvae were (100 & 100 %) and (85.7& 100%) for 2 nd instar larvae for each (treated & untreated), respectively.