Mortality of the European Red Mite (Acarina: Tetranychidae) from Secretion of Peach Leaf Nectaries

Extract

Every spring since it was first noticed in 1947, the first-generation immature stages of the European red mite, Metatetranychus ulmi (Koch), has suffered some mortality in peach orchards of the Niagara Peninsula of Ontario. Sometimes this mortality was negligible but in the cold, wet spring of 1949 it reached 80 per cent in some orchards. Mortality of similar extent has not been noticed on other hosts of the mite at this season; counts of a thousand or more living and dead mites on young shoots of each host at Vineland Station on May 16, 1957, showed apparent mortalities of 53 per cent on Elberta peach, 7 per cent on Italian prune, and 8 per cent on Melba apple. The mortality on peach leaves is difficult to determine, for if the mites are examined too early, many of those killed in the quiescent, premoulting condition cannot be distinguished from living ones, and if they are examined too late, the survivors may have suffered mortality from other causes.