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Beauveria bassiana (Balsamo) is one of the promising microbial control agents for the management of Oryzaephilus surinamensis (L.) Death rate, lethal time and survival expectancy were calculated for an infected population of O. surinamensis at 15, 20, 25, 30 and 35 °C. Results showed that the mean death rate under above mentioned temperatures was 0.89, 1.15, 1.40, 1.21, and 1.11 larvae/day, respectively. The values were 0.99, 1.38, 1.47, 1.18 and 1.16 insects/day for adults respectively. LT₅₀s, at the same temperatures, were 7.11, 7.04, 4.82, 6.07 and 6.89 days for larvae and 7.03, 6.31, 4.83, 5.58, and 6.55 for adults, respectively. Survival curves for both larval and adult populations were more similar at 25, 30 and 35 °C compared to 15 and 20 °C. The survival rates in infected populations were low during 3^rd and 4^th days post inoculation and decreased with a sharp slope toward the end of the experiments under different temperatures. In every case, survival curves were of the 2^nd type in which the mortality decreases in a steady linear form.

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The entomopathogenic-fungus-life cycle is associated with the synthesis and secretion of a number of toxic metabolites, including extracellular enzymes and the low-molecular weight compound (toxin). The potential for a successful pathogen relies on the ability to overcome the various host-defence systems. Interaction between the fungus, Tolypocla-dium (Deuteromycetes), its secondary metabolite, and its host cellular defence were inves-tigated using in vivo and in vitro studies. In vitro studies showed that toxins (efrapeptins) inhibit phagocytic activity of Galleria mellonella (Lep: Pyralidae) haemocytes. The effect of efrapeptins on phagocytosis was in a dose-dependent manner i.e. the amount of phago-cytosis in a treated cell-culture with 0, 3, and 30 g efrapeptins per well was about 12, 7.5, and 4.5 %, respectively (P<0.05). In vivo studies showed that injection of insects with 0, 0.25, and 0.025 g toxin rendered percentages of phagocytosis of 13, 11.5, and 7.2, respec-tively (P<0.05). There was no significant reduction in the total haemocyte count (THC) when larvae were injected with Tolypocladium cylindrosporum spores until 24 hours fol-lowing injection. However, THC was suppressed at 48 hours post-treatment of larvae with spores. Considering that toxin suppresses phagocytosis, nodule formation, but not THC, this study suggests that efrapeptins may interfere with the ligand-receptor interactions that are likely to occur in the plasma membrane of specific haemocytes.

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The European Corn Borer (ECB) is one of the most important insect pests of corn and some other crops such as rice in Iran. This pest is one of the most important hosts of the entomopathogenic fungus Beauveria bassiana, a well known fungal entomopathogen with high host range and considerable potential in insect pest control. In an isolate selection program of fungal isolates against ECB, ten isolates consisting of eight isolates from Iran and two from other countries were assayed using the dipping method on third instar larvae of ECB. Inoculum concentrations were 104, 105, 106, 107, and 108 conidia ml-1. For each concentration, 30 larvae were dipped into the conidial suspension for 30 secends. Control larvae were treated with distilled water containing 0.03 percent Tween-80 as surfactant. Each experiment was repeated three times. Results showed that BEH isolate which was isolated from the soil of insects living in the field, caused the highest mortality in larvae in comparison with other isolates with a mean of 57.67 percent mortality using 108 conidia ml-1. Other isolates, such as DEBI007 and EVIN I, were scored in the lower position with producing 53.43 and 42.67 percent mortality, respectively. EVIN II, DEBI002, and DEBI008 caused the lowest mortality in assayed larvae. A decrease in larval feeding was detectable a few days before death. Possible causes for the low mortality in isolates are discussed.

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The number of active substances registered for wireworm control is decreasing. Consequently, inventorization programs were launched to find and identify potential wireworm biological control agents. Metarhizium brunneum Petch was isolated from an adult Agriotes sp. (Coleoptera: Elateridae) in Slovenia. The strain belongs to a phylogenetic lineage of M. brunneum accommodating isolates from Asia and North America while it was reported from Europe (Denmark and Switzerland) only recently, and for the first time in Slovenia. Its pathogenicity to field-collected Agriotes spp. was tested in feeding and soil experiments. The latter lasted either 15 or 90 days and adopted different concentrations of fungal conidia. Coating potato slices with conidia had no effect on mortality. However, M. brunneum in soil significantly increased wireworm mortality in short- and long-term bioassays. The average LT₅₀ based on Probit analysis was 44.6 days for the M. brunneum treated wireworms and 741 days for the negative controls.

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