Fungus strain
A strain of M. anisopliae designated “Strain 150” was used in this research. It was obtained from a culture collection of entomopathogenic fungi kept in our laboratory. It was originally isolated from infected larvae of the ground beetle Harpalus caliginosus (Carabidae, Coleoptera). Morphological and molecular characteristics of the fungus species which confirmed its identity as M. anisopliae were formerly confirmed by our laboratory and the laboratory of molecular biology at An-Najah National University. These characteristics were conforming to those described by other investigators for the genus and species of the fungus ( Bridge et al., 1993; Bischoff et al., 2009). For bioassays, the fungus strain was sub-cultured on plates of Sabouraud dextrose agar (SDA) culture medium, then incubated at 20 ± 1 °C for 16 days to produce large numbers of conidia. The conidia produced were harvested then suspended in sterile distilled water containing 0.1% (v/v) Tween 20 using 250 ml screw capped glass bottles. The suspension produced was vigorously shaken for few minutes to get a homogenous suspension then sieved using a small-mesh piece of sterile cheese-cloth to separate the mycelium fragments of the fungus from other constituents of the suspension. A haemocytometer was used for counting the conidia of the original suspension before making any dilution. The concentration of conidial suspension used for bioassays was adjusted at 5.0 × 107 conidia/ml. The choice of this concentration is attributed to the range of effectiveness of this strain against many insects which varies from 1.0 × 107 to 1.0 × 108 conidia/ml (Batta, 2005). Viability of the conidia that were used for bioassays and suspended in the conidial suspension was measured by calculating the % conidia that can germinate. The germination of conidia was based on the formation of a short germ tube when the conidia were suspended in water for 24 h. The calculated % of conidia that germinated after the suspension was 80.2%.