Harmful and Harmless Soil-Dwelling Fungi Indicate Microhabitat Suitability for Off-Host Ixodid Ticks.

Following blood meals or questing bouts, hard ticks (Ixodidae) must locate moist off-host microhabitats as refuge. Soil-dwelling fungi, including entomopathogenic Beauveria bassiana ( Bb ), thrive in moist microhabitats. Working with six species of ixodid ticks in olfactometer bioassays, we tested the hypothesis that ticks avoid Bb . Contrary to our prediction, nearly all ticks sought, rather than avoided, Bb -inoculated substrates. In further bioassays with female black-legged ticks, Ixodes scapularis , ticks oriented towards both harmful Bb and harmless soil-dwelling fungi, implying that fungi-regardless of their pathogenicity-signal habitat suitability to ticks. Only accessible Bb -inoculated substrate appealed to ticks, indicating that they sense Bb or its metabolites by contact chemoreception. Bb -inoculated substrate required ≥24 h of incubation before it appealed to ticks, suggesting that they respond to Bb metabolites rather than to Bb itself. Similarly, ticks responded to Bb -inoculated and incubated cellulose but not to sterile cellulose, indicating that Bb detection by ticks hinges on the Bb metabolism of cellulose. 2-Methylisoborneol-a common fungal metabolite with elevated presence in disturbed soils-strongly deterred ticks. Off-host ticks that avoid disturbed soil may lower their risk of physical injury. Synthetic 2-methylisoborneol could become a commercial tick repellent, provided its repellency extends to ticks in diverse taxa.