Asael Rot and Michael Samish - Kimron Veterinary Institute, P.O.B. 12, Bet-Dagan, 50250 Israel
Efficacy of two entomopathogenic hyphomycetes fungi, Metarhizium anisopliae var.
acridum (M. an. ac.) and M. anisopliae var. anisopliae (M. an. an.) was evaluated against eggs of
three tick species – Hyalomma excavatum, Rhipicephalus annulatus and Rhipicephalus sanguineus.
Eggs laid by surface-sterilized females were spread on conidia-impregnated filter paper. Although M.
an. an. differed in their virulence to the tested ticks, they reduced the hatching percentages of eggs of
all three tick species to 0–32% compared with 80–90% in the control eggs. The M. an. ac. strains were
highly virulent to H. excavatum and R. sanguineus eggs, reducing the hatching percentages to 2–6 %,
but had no influence on hatching of R. annulatus eggs. The effects of lipid fractions from tick eggs
surface on the development of conidia were tested. Both germination of M. an. an. conidia and the
formation of appressoria were stimulated by extracts from egg cuticles of all three tested tick species.
However, the stimulating effect was lower when the conidia were exposed to lipids from relatively
less susceptible R. annulatus eggs than when exposed to lipids from H. excavatum or R. sanguineus
eggs. Conidia of M. an. ac. exposed to such lipid extracts did not germinate or form appressoria.
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