Three compounds, guanine, xanthine and hematin, were found to contribute to the arrestment response in Ixodes scapularis. Guanine and xanthine were identified in acidified saline extracts of cast skins and tick excreta. The compounds were purified by HPLC and their identification confirmed by liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance spectrometry (NMR). Hematin was found in NH4OH extracts of black excreta from unfed and feeding ticks. Ammonia, also believed to contribute to the arrestment response, was detected in excreta from feeding ticks. Petri dish bioassays using visual observations and video tracking with a CCD video camera and EthovisionTM software demonstrated a strong positive arrestment response to cast skins, fecal extracts and artificial mixtures containing guanine, xanthine and hematin. Guanine and xanthine induced only weak arrestment responses but hematin was highly stimulatory. Incorporating the pheromone components in an oily matrix (Last CallTM) also containing permethrin increased product lethality from 65% without pheromone to 95% with pheromone. More detailed knowledge of I. scapularis arrestment pheromone may be useful for improving the efficacy of this tick-killing technology even further. Field tests to evaluate the efficacy of this tick-killing technology for control of I. scapularis populations under natural conditions are planned.
Species 1: Acari Ixodidae Ixodes scapularis (Blacklegged tick)
Keywords: Pheromone chemistry
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