Fungus
The M. brunneum strain 7 (previously M. anisopliae-7) used in all experiments in this report was isolatedtwo decades ago from an unidentified beetle collected in Israel. The fungus was cultivated on Sabouraud dextroseagar (SDA) at 25◦C in the dark, while passing twice ayear through engorged R. annulatus ticks. For field experi-ments, the fungus was cultivated on media made by adding400 g “organic” wheat to 1 l water and then autoclaving for40 min at 127◦C in plastic bags. The medium in each bagwas inoculated with 25 ml of spore suspension (1 × 106spore/ml with 0.01% v/v Triton X-100) and incubated at28◦C for 2–3 weeks until sporulation. Then, conidia werecollected from the wheat suspension with distilled watercontaining 0.01% Triton X-100 and filtered through Mir-acloth (Calbiochem, La Jolla, CA). Conidial concentrationswere determined by hemocytometer. A concentration of1 × 108conidia/ml in distilled water containing 0.01% Tri-ton X-100 was used for all experiments unless otherwisespecified. The percentage of viable conidia was determinedby counting germination on SDA 1 day prior to each bioas-say. Only suspensions containing at least 95% viable conidiawere used.