Effects of pyriproxyfen on off-host water-balance and survival of adult lone star ticks (Acari: Ixodidae).
Newly engorged nymphs of the lone star tick, Amblyoma americanum (L.), were continuously exposed to 4 microg/cm2 of pyriproxyfen residues in glass vials. Treatment of engorged nymphs (n = 285) resulted in significant molting inhibition, with more than one-fourth (26.7%, n = 76) of nymphs dying before or during ecdysis. Treatment effects were evident among ticks that molted to the adult stage, with 26.7% (n = 76) of females, and 17.9% (n = 51) of males exhibiting moribund physical characteristics (i.e., lethargy; dull, discolored and desiccated cuticles; lacking full locomotor competency). A few molted adult ticks (10 males, four females) were dead upon inspection. Only 11.2% of pyriproxyfen treated, emergent females (n = 32), and 11.5% of treated emergent males (n = 25) from 285 ticks treated as engorged nymphs, exhibited normal physical appearance and possessed a full range of locomotor activity. Treated adult ticks maintained within a desiccating environmental chamber at 0% RH and 23 degrees C, had significantly accelerated whole-body water loss rates in comparison to untreated males and females maintained under the same environmental conditions. Additionally, treated adult ticks maintained under optimal environmental conditions (23 degrees C and >95% RH) sustained 100% mortality within 32 d following assignment to these conditions (or 79 d posttreatment as engorged nymphs), whereas untreated ticks had 0% mortality for the same duration of time. Results demonstrate that continuous exposure of nymphs to pyriproxyfen disrupted molting, and accelerated both whole-body water loss and subsequent mortality among emergent adult ticks.
Strey
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Department of Entomology, Texas A&M University, College Station 77843-2475, USA.
Teel
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Longnecker
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D000818:Animals; D001834:Body Water; D005260:Female; D007605:Juvenile Hormones / Q000494:pharmacology*; D008297:Male; D011725:Pyridines / Q000494:pharmacology*; D013983:Tick Control; D013987:Ticks / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology
D007605:Juvenile Hormones; D011725:Pyridines; C055613:pyriproxyfen