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Ability of Two Natural Products, Nootkatone and Carvacrol, to Suppress Ixodes Scapularis and Amblyomma americanum (Acari: Ixodidae) in a Lyme Disease Endemic Area of New Jersey

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We evaluated the ability of the natural, plant-derived acaricides nootkatone and carvacrol to suppress Ixodes scapularis Say and Amblyomma americanum L. Acari Ixodidae. Aqueous formulations of 1 and 5 nootkatone applied by backpack sprayer to the forest litter layer completely suppressed I. scapularis nymphs through 2 d. Thereafter, the level of reduction gradually declined to -50 at 28 d postapplication. Against A. americanum nymphs, 1 nootkatone was less effective, but at a 5 concentration, the level of control was similar or greater to that observed with L scapularis through 21 d postapplication. Initial applications of 0.05 carvacrol were ineffective, but a 5 carvacrol formulation completely suppressed nymphs of both species through 2 d and resulted in significant reduction in I. scapularis and A. americanum nymphs through 28 and 14 d postapplication, respectively. Backpack sprayer applications of 5 nootkatone to the shrub and litter layers resulted in 100 control of I. scapularis adults through 6 d, but the level of reduction declined to 71.5 at 28 d postapplication. By contrast, high-pressure applications of 2 nootkatone to the litter layer resulted in 96.2-100 suppression ofboth L scapularis and A. americanum nymphs through 42 d, whereas much lower control was obtained from the same formulation applied by backpack sprayer. Backpack sprayer application of a 3.1 nootkatone nanoemulsion resulted in 97.5-98.9 and 99.3-100 reduction in I. scapularis and A. americanum nymphs, respectively, at 1 d postapplication. Between 7 d and 35 d postapplication, the level of control varied between 57.1 and 92.5 for I. scapularis and between 78.5 and 97.1 for A. americanum nymphs. The ability of natural products to quickly suppress and maintain significant control of populations of these medically important ticks at relatively low concentrations may represent a future alternative to the use of conventional synthetic acaricides.

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  • Biology
  • Medicine and Medical Research

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