EFFECTS OF PYRIPROXYFEN ON ENGORGED FEMALES AND NEWLY OVIPOSITED EGGSOF THE LONE STAR TICK (ACARI, IXODIDAE)

Engorged females and 1- to 3-d-old eggs of the lone star tick, Amblyom ma americanum (L.), were exposed to 9 treatments of pyriproxyfen (4, 8 , and 16 mu g/cm(2)) in glass vials at exposure periods of 7 d, 14 d, and continuous at each dosage level. Treatment of newly engorged femal es did not affect the number of females ovipositing, but the number of eggs oviposited decreased as dosage and exposure time increased. Comp lete inhibition of egg hatch occurred at all treatment levels except t hat of the lowest dosage and exposure time where 99.9% inhibition was observed. Egg masses from treated. females contained eggs that turned a dark amber color and imploded, retained normal shape and color witho ut visible evidence of embryogenesis, or had developed embryos that we re unable to emerge. Treatments of 1- to 3-d-old eggs were effective i n reducing hatch and larval survivorship to 25 d after emergence only at the continuous exposures of dosages of 4, 8, and 16 mu g/cm(2). Lar vae emerging from eggs treated at the lower dosage rates of 0.2 and 0. 02 mu g/cm(2) were as successful in feeding on chickens and subsequent ly molting as acetone treated control ticks.