An-Najah Staff

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