Pyriproxyfen Effects on Newly Engorged Larvae and Nymphs of the Lone Star Tick (Acari: Ixodidae)

Abstract

Newly engorged larvae and nymphs of the lone star tick, Amblyomma americanum (L.), were exposed to 9 treatments of pyriproxyfen in glass vials consisting of dosages of 4, 8, and 16 μg/cm2 for 7 d, 14 d, and continuous exposure periods at each concentration. Treatment of newly engorged larvae resulted in decreased molting, altered postmolt defecation, and nymphal survival with results being dose and exposure dependent. Molting inhibition ranged from 35.9 to 68.4%. Successfully molted nymphs were lethargic, exhibited altered defecation patterns, and were short-lived compared with untreated adults. By 65 d after treatment, cumulative inhibition of molting and hastened mortality of molted adults resulted in 82.6-100% control, depending on dosage and exposure. Treatment of newly engorged nymphs showed minimal to no effect on molting; however, adults were lethargic and displayed altered postmolt defecation patterns. Subsequent adult longevity was most dramatically affected with 87.9-100% control achieved by 82-84 d after treatment. Fecal patterns and survivorship were dose and exposure dependent. Estimates of subsequent feeding success of adults treated as engorged nymphs, show reduced capacities of attachment, engorgement and reproduction.