An-Najah Staff

Formulations of Metarhizium anisopliae conidia with oven ash, chalk powder, charcoal and wheat flour at a ratio of 1:4 (W/W) were prepared. Formulations containing charcoal and oven ash had a conidial viability half-life of 4.1–4.3 months at 2071!C. In comparison, unformulated conidia held under the same conditions had a viability half-life of 0.9 month. Bioassays carried out at 2872!C and 7075% RH indicated that the treatments with charcoal and oven ash formulations at a rate of 2.0% or 2.8 mg/cm2 of treated area resulted in 73.3–86.7% mortality of adult Sitophilus oryzae after 7 days when treatments were applied before or after pest infestations. Mortality in F1 adults was 28.9–47.5% when exposed, upon emergence, to the same formulations previously applied against their parents. Treatments applied before pest infestation with charcoal or oven ash formulation reduced damage rates to wheat grains to 0.5% compared to the control (6.0%). Development time of S. oryzae was prolonged 4–8 days when the grains were treated before pest infestation with fungal formulations in charcoal or oven ash. A synergistic effect between the fungus and the most effective dusts, charcoal or oven ash, for the ‘‘after pest infestation’’ treatments was obtained during bioassays for evaluation of S. oryzae adult mortality. Additional experiments are required to explain the mechanism of this synergism.

Laboratory bioassays were conducted in order to evaluate the use of the entomopathogenic fungus, Metarhizium anisopliae (Metschinkoff) Sorokin (Deuteromycotina: Hyphomycetes), against adults of three stored-grain beetle species, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae). Two fungal preparations were compared, a conidial suspension and a conidial powder. These were applied to wheat, at three dosages, 8
106 , 8
108 and 8
1010 conidia/kg of wheat, alone, or in combination with the diatomaceous earth (DE) formulation SilicoSecs (Biofa Gbmh, Germany), applied at 0.5 g/kg of wheat. Adult insects were exposed to treated wheat for 24 h, 48 h,7 d and 14 d. The mortality of R. dominica adults after 14 d of exposure to the treated substrate was 100% and 96% at the dosages in combination, for the suspension and the powder, respectively. The respective figures without DE were 94.4% and 74.6%. In contrast, against S. oryzae adults, the application of conidial suspension combined with DE was not as effective as the application of DE alone. Adult mortality of S. oryzae increased notably on wheat treated with the conidial powder. Similarly, the conidial suspension, with or without DE, was not as effective against T. confusum as the conidial powder. The progeny production of R. dominica on wheat treated with the highest suspension dosage, with or without DE, was significantly lower than that for the other aqueous fungal dosages. Moreover, significantly less progeny were produced on wheat treated with the highest dosage of powder conidia combined with DE, in comparison with the other treatments. In contrast, S. oryzae progeny production was notably reduced only in wheat treated with the highest dosage of fungal spore powder mixed wit