SIDE-EFFECTS OF ORGANIC SCAB FUNGICIDES .1. LEAF-SPOT AND LEAF DROP OF GOLDEN DELICIOUS APPLE-TREES

Scab fungicides with the active ingredients captan, metiram, propineb, thiram, dichlofluanid, dithianon, mancozeb and ferbam (ferbam applied only before flowering) were tested for their side-effects on leaf spot and leaf drop of ''Golden Delicious'' apple trees. The applications of captan, dithianon and ferbam/captan (preblossom/postblossom application) led to considerably more leaf spot than thiram, mancozeb and propineb. The effect of metiram was intermediate between these groups. A similar classification of these compounds with regard to their influence on premature leaf drop was observed. The effect of the fungicides on this physiological disorder could only be found under conditions of heavy leaf drop. After-effects on leaf spot and leaf drop in the following year, with no further trial applications, could not be observed.