An-Najah Staff

The present study included treatments of stored wheat grains with four types of dusts alone or in combination with conidia of the entomopathogenic fungus Metarhizium anisopliae. A ratio of 1:4 (w/w of the fungus conidia to the dust carrier, respectively), and a rate of application of 2.0% (w/w of the dust carrier alone or the dust carrier + fungus conidia to wheat grains) were used during the treatments. Results obtained have shown that the treatments with combination of charcoal + fungal conidia, oven ash + fungal conidia, and chalk powder + fungal conidia caused significant higher percentage of Tribolium castaneum-adult mortality (73.3, 53.3, and 60.0%, respectively) compared to treatments with charcoal, oven ash, and chalk powder alone (13.3, 26.7, and 13.3% respectively). Significant reduction in the percentage of insect infestation rate on wheat grains was also obtained when treatments with the above-mentioned combinations were compared with the dust treatment alone. The least significant percent of infestation rate was thus obtained with oven ash + fungal conidia (0.5%) followed by charcoal + fungal conidia (1.2%) then, chalk powder + fungal conidia (2.0%). Moreover, significant longer durations of T. castaneum life-cycle were obtained after treatment with charcoal + fungal conidia (54.7 days) and chalk powder + fungal conidia (60.0 days) compared with treatments with charcoal and chalk powder alone (48.0 and 53.7 days, respectively). This demonstrates clearly the effect of treatment on retardation of the insect development by > 6 days. Further experiments under a wide range of temperature and relative humidity and on larger quantities of wheat grains are recommended to be carried out before applying the effective combinations of the fungus and dust carriers at a large scale for control of this insect.

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.