An-Najah Staff

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.

An invert emulsion (water-in-oil formulation) based on coconut and soybean oils provided the most stable emulsion layer (93% V/V) and lowest viscosity (27±0.81 cps), suitable for a formulation of Trichoderma harzianum conidia. Conidia remained viable for 36 months (shelf-life) with 50% reduction in viability (half-life) after 5.3 months at 20±1°C., compared with 2.7 and 0.7 months, respectively, for dry non-formulated conidia. Stability and viscosity of the formulation remained constant during the time period of viability study. Bio-assay tests on wounded apple fruit indicated the presence of significant preventive effect of formulatedTrichoderma conidia against the causative organism of apple gray mold Botrytis cinerea. The diameter ofBotrytis lesions was significantly reduced (P<0.05) 5 days after inoculation and treatment with formulatedTrichoderma conidia. Botrytis sporulation on the lesion surface was also inhibited 10 days after inoculation. These results were confirmed under simulated natural conditions by spraying a Botrytis conidial suspension on microwounded apple fruit following treatment by dipping fruit. Treatment of healthy non-wounded apple fruits resulted in protection from Botrytis infections for >2 months following inoculation and treatment.