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.
Treatments with conidia of the entomopathogenic fungus Metarhizium anisopliae formulated in invert emulsion (water-in-oil formulation) or in wheat flour were applied to Rhyzopertha dominica adults infestingCicer arietinum grains. The application rates were 4.1×105 conidia/cm2 of treated area using a concentration of 1.8×107 conidia/ml of the invert emulsion and 8.2×106 conidia/cm2 of treated area using a concentration of 6.5×108 conidia/g of the wheat flour formulation. Results have indicated significant mortality (P<0.05) when newly emerged R. dominica adults were introduced and then treated with the invert emulsion and wheat flour formulations (86.7–93.3%, control treatment 10.0–26.7% mortality). When treated grains were left until the emergence of F1 adults, there was also significant mortality (P<0.05) in both treatments (28.3–60.0%, control treatment 1.7–8.3% mortality). This indicates a residual effectiveness of the treatment with the two formulations against R. dominica adults which extended to >2 months (equivalent to the duration of the insect life-cycle at 23±2°C and 75±5% r.h.). Infestation rate of C. arietinum grains by R. dominica at 23±2°C and 75±5% r.h. was significantly reduced in the treatments with the fungal conidia formulated in invert emulsion (0.7%) or in wheat flour (1.0%) when compared with the control treatment (19.0–23.3%). The preventive treatments significantly retarded R. dominica development (P<0.05) by 8–12 days compared with the control treatment. The infection with the fungus thus delayed adult emergence of R. dominica by 8–12 days. Overall results give promise for control of R. dominica with M. anisopliae mixed with wheat flour or introduced into invert emulsion.