The present study was carried out to evaluate the biochemical effects of seven culinary and medicinal plant oils namely: garlic (Allium sativum L.), onion (Allium cepa L.), olive (Olea europaea L.), rosemary (Rosmarinus officinalis L.), sunflower (Helianthus annuus L.), peppermint (Mentha piperita L.) and camphor (Eucalyptus globulus) on Trogoderma. granarium treated as 4th instar larvae. According to these evaluations, the potential insecticidal properties of these oils could be assessed. Data obtained indicated that exposure of the 4th instar larvae of T. granarium to concentrations ranged from 0.025 to 1.0 ml per ten gm of wheat resulted in inhibition of adult fecundity. The total inhibition of new generation started at 0.3 ml when using garlic and sunflower. On the other hand, when using onion, olive, and rosemary oils the prevention observed at 0.15 and when using camphor and peppermint oils the prevention was at 0.1ml. The results showed that glucose (as an indicator of carbohydrate metabolism) and lipid content in treated larvae was less than in control and protein content was higher. This could be due to the greater protein synthesis by the fat body and other tissues with plant oil (as insecticide) treatment, since protein helps to synthesize microsomal detoxifying enzyme which assists to detoxify the toxicants that entered into the animal body. As for lipid content another explanation for the decrease of its content could be due to the disturbance in corpora allata or that plant oils act as juvenile hormone. The alkaline phosphatase (ALP) activity in treated larvae was less than in control one when using garlic, onion, sunflower, and rosemary oils in the treatment while its content increased than in control when using olive, peppermint and camphor oils. This means that all tested oils have a juvenile hormone effect. Acid phosphatase (ACP) content in treated larvae was found to be less than in the control and that could be due to the presence of anti-insect protein in the tested oils that its defense function is correlated with acid phosphatase activity and cause loss of acid phosphatase activity. Cholinesterase was found to be increased and that could be due to the inhibition of detoxifying enzymes. The results show that both alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in 4th instar larvae were found to be decreased and the decrease of AST was found to be more than ALT.
Key words: Stored product pests, Trogoderma granarium, Plant oils, Biochemical parameters