Effect of Neem, Siam Weed and Vetiver Oils on Physiological Reactions and Fitness of House Fly, Musca domestica L

Insecticidal activities of hexane extracts of leaves and roots of siam weed and vetiver, and roots of neem were assessed against house fly, Musca domestica L. Mortality test was conducted using serial concentrations 20%, 10%, 5% and 2.5% of extracted oils while behavioural orientation of house fly to oil odour, antioviposition effect of oil toward the insects, biochemical reactions in treated flies and fitness of offspring were determined using 20% oil concentration. House fly mortality varied significantly with plant species and part of plant extracted (P 0.001), concentration applied (P 0.001) and time post-exposure (P 0.001). All tested plant extracts showed potential as good control agents with average mortality ranging from 59-74%. However, significantly lower median lethal values (LC_50 and LT_50) separated vetiver as the most toxic plant against the insect pest. The plant oils repelled house flies (93-100%), reduced the number of larvae that hatched from laid eggs, lowered adult emergence and caused a significant reduction in size and weight of offspring. On the contrary, exposure to plant oils did not alter offspring sex ratio. In comparison to untreated house flies, plant oils induced biochemical stress in poisoned cohorts as evidenced in significant deviation of digestive enzyme (α- and β- amylases, lipase) activity and concentrations of detoxifying enzyme (glutathione-Stransferase), neurochemical enzyme (acetylcholinesterase) and energy metabolism biomolecules (total protein). Implications of obtained results for non-chemical control strategies are discussed.