EFFECTS OF MITICIDES ON THE LIFE STAGES OF THE EUROPEAN RED MITE, PANONYCHUS ULMI (KOCH) (ACARI: TETRANYCHIDAE)

Abstract In laboratory tests, many miticides affected more than one life stage of the European red mite but most showed greater toxicity to one specific stage. Most were more toxic to nymphs and adults than to eggs. Cyhexatin was more toxic to nymphs whereas fenbutatin-oxide was more toxic to adults than to nymphs. Propargite, formetanate HCl, and dinocap were more toxic to nymphs than to adults. Dicofol and oxythioquinox were more toxic to adults than to nymphs. Dienochlor was the least toxic miticide tested, and was more toxic to nymphs and adults than to eggs. Amitraz, permethrin, and fenpropathrin were repellent to motile stages at low concentrations, but amitraz was also highly ovicidal. Clofentezine and hexythiazox were toxic to eggs and nymphs but not to adults. Affected nymphs developed into the deutochrysalis or teleiochrysalis stages but were unable to eclose from these quiescent stages. In field trials, applications timed to coincide with a predominance of sensitive stages were successful. Early season applications suppressed mite numbers for much of the growing season. Populations exhibiting considerable synchrony occurred into August suggesting that susceptible stages could be targeted for control throughout the season.