INFLUENCES OF SOME FUNGICIDES ON ORCHARD MITES IN BRITISH COLUMBIA

Abstract

In apple orchards of the commercial fruit growing areas of British Columbia, nine fungicides gave the following results in the control of mites: a fungicide schedule consisting of four to seven sprays of lime-sulphur gave excellent control of Metatetranychus ulmi (Koch), but one spray applied at the pink stage gave control for only 2 months. Three summer sprays of elemental sulphur did not affect M. ulmi, but controlled Tetranychus telarius (L.) and Vasates schlechtendali (Nal.). A schedule of ferbam gave good control of Eotetranychus carpini borealis (Ewing). Four to seven sprays of captan favoured increases in numbers of M. ulmi and E. carpini borealis. M. ulmi also increased in numbers after five applications of ziram. A schedule of glyodin did not control any species; in some cases the numbers of M. ulmi and E. carpini borealis increased after applications of this fungicide. A schedule of maneb controlled M. ulmi and V. schlechtendali, delayed the peaks in populations of T. telarius and E. carpini borealis, but allowed large numbers of Bryobia arborea M. & A. Manam compared favourably with maneb against M. ulmi and T. telarius. One spray of Karathane controlled any species if the application was timed correctly.Predatory mites, Typhlodromus spp., were not affected by glyodin but were reduced in numbers by ziram and nearly eliminated by maneb and Karathane. Mediolata sp. was slightly reduced in numbers by glyodin but maneb was somewhat more toxic and Karathane eliminated it. One spray of Karathane killed only 27 per cent of Stethorus picipes Csy.Ferbam, maneb, and Karathane promoted tree vigour; large, healthy, dark-green leaves were characteristic of trees sprayed with these fungicides.