Comparison of the effects of Altozar and DDT on females of Ixodes persulcatus Sch. during and after feeding.

Ixodes persulcatus females were treated with Altozar and DDT at one of six consecutive time-points during the period beginning with attachment and ending with the commencement of oviposition. The moment of tick attachment (point 1) appeared to be the most sensitive time for the action of Altozar; a delay of detachment of some of the engorged females was observed, as well as a decrease in their mean weight and the non-detachment of a considerable number of the females over a long period. Similar effects were observed when Altozar was applied on the first and third days after attachment (points 2 and 3), although in the first case they were less pronounced. Altozar treatments on the fifth day of feeding, shortly before oviposition, and especially immediately after detachment (points 4, 5 and 6, respectively) mainly resulted in non-viability of the eggs. DDT was ineffective when it was applied at point 1. DDT treatments of ticks at points 3 and 5 were highly effective; this was expressed by a reduction in weight of the engorged females and a suppression of their fecundity at point 3, and death of all the larvae at different times after hatching at point 5. Many larvae also perished when the ticks were treated with DDT at point 6. Ticks were quite tolerant to DDT action when they were treated at points 2 and 4. The action of both compounds ultimately resulted in the inhibition of tick reproduction, but the rate and method depended on the compound applied as well as on the time of treatment. Altozar effects after treatment at points 1-3 may be considered to be hormonal.