The Efficacy of Zingiber officinale (Ginger-Zingiberaceae) Crude Extracts Applied as Individual and Mixed with Dennettia tripetala (Pepperfruit-Annonaceae) against Musca domestica (Housefly) Larvae

Aims: To evaluate the efficacy of Zingiber officinale applied individually and mixed with Dennettia tripetalain equal proportions; their insecticidal strength was also compared using dipping and feeding techniques.

Methodology: Insects were cultured in cages (30 cmx30 cmx30 cm) built with wood, nets and gauze at the Department of Animal and Environmental Biology Laboratory. Freshly emerged larvae (1 day old) were used for the bioassay. The cages were placed on plastic stands which contained engine oil to prevent infestation of other insects and mites. 20 larvae each, were transferred into petri dishes containing larvae food (2 ml of powdered milk mixed with distilled water) using fine art brush.The plants (Z. officinale) rhizome D. tripetalafruits were purchased from the market. Z. officinale rhizome was sliced into tiny pieces while D. tripetalaskin was peeled off to obtain the seeds. They were dried at ambient temperature (28±2°C) for four weeks, afterwards they were grounded with an electric blender (Philips) and sieved with 0.1mm mesh size sieve to obtain fine powder which was stored in an airtight container to prevent the active ingredients from evaporating and kept in a cupboard until the time for use. The crude extracts were obtained by homogenizing 10 g of dust (plant sample) with 100 ml (80/20) of solvents (v/v) (hydro-ethanol) and left for 24 hours thereafter, it was filtered with a filter paper and the residue (active compound) was evaporated over a water bath at 40°C. To obtain the final concentration; the extracts were dissolved in a known volume of distilled water; for example, 200, 400, 600, 800 and 1000 ppm were obtained by dissolving 0.2, 0.4, 0.6, 0.8 and 1.0 mg of extract in a ml of distilled water. Mortality and means were monitored every 12 hours for 72 hours. The experiment was replicated twice with distilled water serving as control. The toxicity was also tested using dipping and feeding techniques.

Results: Showed the mortality observed within a period of 72 hours, percent mortality and probit mortality of Z. officinale on M. domestica larvae using dipping and feeding technique. The result showed that mortality was significant (P<0.05) as concentrations increased from 200-1000 ppm but mortality was not significant as duration of exposure increased from 12-72 hours. The LC50 and LT50 were 0.4898 mg/ml and 40 hours. No mortality was observed when the insects were fed with crude extracts but they (insect larvae) were weakened (their movement was sluggish and they did not pupate. When Z. officinale and D. tripetalawere mixed in equal proportions using dipping and feeding techniques, mortality of the larvae was generally significant (p<0.05) as both concentrations and duration of exposure increased. When they were dipped in the mixed crude extract, LC50 and LT50 of 0.2754 mg/ml and 30 hours were obtained while LC50 and LT50 of 0.4786 mg/ml and 44 hours were obtained when they were fed with the mixed crude extract.