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.

The present research aimed at describing the macroscopic and microscopic symptoms of infection with the entomopathogenic fungus Metarhizium anisopliae on tobacco whitefly (Bemisia tabaci) and red spidermite (Tetranychus cinnabarinus). For this, conidial suspensions of the fungal strain Meta 1 were applied against larvae and pupae of B. tabaci, and adults and nymphs of T. cinnabarinus infesting eggplants under laboratory and simulated field conditions. Results obtained have indicated that infected larvae and pupae of B. tabaci turned into black-greenish color due to the fungus-attack 3 days after treatment and incubation at 20+-1degreeC and 100% RH using two types of incubation techniques. Infected nymphs and adults of T. cinnabarinus also turned into dark-brown color 3-4 days after treatment and incubation under similar conditions to B. tabaci. The same color change in both pests due to the fungus-infection under simulated field conditions (19-30degreeC and >90% RH) was also obtained. Dark-brown fungal outgrowth and sporulation was observed on the cadavers of treated individuals with the fungus in both pests 5 days after treatment and incubation under the above-mentioned conditions. Microscopic examination of infected individuals of B. tabaci or T. cinnabarinus have indicated that typical mycelia and conidia of M. anisopliae were observed on their surface. Moreover, dense mycelial growth of the fungus was also observed under higher microscopic magnifications in the hemocoel of attacked individuals of B. tabaci or T. cinnabarinus. The latter observation was realized after a careful superficial sterilizaton of the infected individuals of both pests, then mounting and clearing them in lactophenol before examination. Overall results refer to the possibility of using the fungus in biocontrol of both pests.

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 experiments were carried out in order to assess the insecticidal effect of Metarhizium anisopliae (Metschinkoff) Sorokin (Deuteromycotina: Hyphomycetes) formulations against larvae of Tribolium confusum Du Val (Coleoptera: Tenebrionidae) on flour and wheat. M. anisopliae was applied at three dose rates, of 8
106 , 8
108 and 8
1010 conidia/kg to either wheat or flour, respectively. Also the wheat/flour was treated with the diatomaceous earth (DE) formulation SilicoSec (Biofa, Germany), at two dose rates, 0.2 and 0.5 g/kg of wheat or flour either alone or in combination withM. anisopliae with each fungal rate. Mortality ofT. confusum larvae was assessed 7 days after exposure to the treated substrate. The bioassays were conducted at three temperatures, 20, 25 and 301C, and two relative humidity (r.h.) levels, 55% and 75%. Larval mortality was notably varied among treatments, as well among temperature and humidity levels. For both fungus and DE, the increase of temperature increased their effectiveness. On the other hand, the increase of r.h. significantly reduced larval mortality for both M. anisopliae and SilicoSec. Both substances, either alone or in combination, were more effective on wheat than on flour. Also, the addition of 0.5 g of SilicoSec in the fungal preparation, especially at the highest dose rate, increased larval mortality, in comparison with the fungus alone or in combination with 0.2 g of SilicoSec. The results of the present work suggest that, under certain circumstances, the effectiveness of M. anisopliae against T. confusum larvae can be benefitted by the presence of DE.

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