Factors influencing the acaricidal activity of flucycloxuron

Contact activities of flucycloxuron on immature stages of the two-spotted spider mite (Tetranychus urticae (Koch)) and the European red mite (Panonychus ulmi (Loch)) gradually decrease in the successive developmental stages. The levels of contact activity of flucycloxuron on larvae and protonymphs of T. urticae and P. ulmi are of the same order. Deutonymphs of T. urticae are less susceptible to contact activity than the similar stage of P. ulmi. In adult T. urticae, the transovarial ovicidal activity was used as an indicator for cuticular penetration. More than 90 % of the maximal penetration into adult mites occurs within 8 h. Reversibility of the transovarial activity was not observed after 24 h, but did occur after a subsequent 48 h stay on untreated leaves