The present investigation aimed to evaluate the efficiency of Bacillus thuringiensis β – exotoxin as a biological agent to control Musca domestica and to study its impact on some biochemical parameters of 2nd larval instar. Laboratory studies are carried by applying topically the bacterium B. thuringiensis β – exotoxin at LC30 under laboratory conditions (27 ± 2°C and 60±5% RH). The total protein contents of the total body, the total lipids, total carbohydrate, enzymatic activities of carbohydrate hydrolyzing enzymes, alkaline and acid phosphatases and non-specific esterases were estimated. Our data revealed that, the total soluble protein contents in supernatant of the homogenated larvae post-treatment was generally decreased, as affected by the tested material at different time intervals as compared to control. As well as a significant reduction in the total lipid content was observed, this may be due to production of enzymes that utilize lipids to remove the invading agent. The total carbohydrate contents was significantly reduced and the reduction was (-14.989, -43.33, 63.93 and -51.69%) with respect to control at the four different time intervals. While the activities of α – and β – esterases were decreased in larvae treated withLC30 of B. thuringiensis israelensis and the reduction of enzymatic activity was highly significant. Alkaline and acid phosphatase showed a significant reduction in its activities. Bacterial treatments induced inhibition in the enzyme activity of invertase where the values of inhibition were (-27.85 , -5.92 , -19.46 and -39.96% ) at different time intervals. Also, a similar reduction of trehalase enzyme activity of treated larvae was observed at different time intervals (-32.81 , 12. 95 , -18.20 and -5.16%). It may be possible in this instance to control flies by the use of this bacterium which incorporate spores and crystals of the appropriate strain of B. thuringiensisisraelensis, by affecting the biochemical systems of the target insect. So, it is quite clear from our results that B. thuringiensis israelensis at concentration of LC30 significantly decreased the activities of all biochemical parameters, we investigated. The general disturbance in metabolism could originate primarily from inhibition of chitin synthesis.
Key words: Housefly, bacteria, biocides, sublethal effects, proteins, carbohydrates, lipids, enzymes.
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