Effect of sodium carbonate and mint oil as additives on the potency of the entomopathogenic bacteria, Bacillus thuringiensis against the cotton leaf worm Spodoptera littoralis (Lepidoptera : Noctuidae)‎

الملخص EN

This study aimed to investigate the effect of adding the inorganic salt, sodium carbonate (Na2CO3) or mint oil to the bio-insecticide, Bacillus thuringiensis (Bay-8, 8% SC) on some of its physico-chemical properties as well as its toxicity in relation to its effect on some biochemical aspects in Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae).

The results clearly showed that adding 0.1% Na2CO3 or 0.3% mint oil to B.

thuringensis solution increased its pH value, viscosity and its toxicity against S.

littoralis 2nd instar larvae, where its LC50 value was reduced from 7.079ml/l to 3.972 and 3.549 ml/l after adding Na2CO3 or mint oil, respectively.

The biochemical studies in the treated larvae with B.

thuringensis combined with 0.1% Na2CO3 or 0.3% mint oil showed a significant reduction in the total protein content, α-esterase and phenoloxidase activities compared to treatment with B.

thuringensis only.

The obtained results confirm the effect of Na2CO3 and mint oil on the activity of these enzymes towards B.

thuringensis, which may explain the increase in the toxicity of B.

thuringensis when mixed with either Na2CO3 or mint oil against S.

littoralis.