| Summary: | Following blood meals or questing bouts, hard ticks (Ixodidae) must locate moist off-host microhabitats as refuge. Soil-dwelling fungi, including entomopathogenic <i>Beauveria bassiana</i> (<i>Bb</i>), thrive in moist microhabitats. Working with six species of ixodid ticks in olfactometer bioassays, we tested the hypothesis that ticks avoid <i>Bb</i>. Contrary to our prediction, nearly all ticks sought, rather than avoided, <i>Bb</i>-inoculated substrates. In further bioassays with female black-legged ticks, <i>Ixodes scapularis</i>, ticks oriented towards both harmful <i>Bb</i> and harmless soil-dwelling fungi, implying that fungi—regardless of their pathogenicity—signal habitat suitability to ticks. Only accessible <i>Bb</i>-inoculated substrate appealed to ticks, indicating that they sense <i>Bb</i> or its metabolites by contact chemoreception. <i>Bb</i>-inoculated substrate required ≥24 h of incubation before it appealed to ticks, suggesting that they respond to <i>Bb</i> metabolites rather than to <i>Bb</i> itself. Similarly, ticks responded to <i>Bb</i>-inoculated and incubated cellulose but not to sterile cellulose, indicating that <i>Bb</i> detection by ticks hinges on the <i>Bb</i> 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.
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