CONTROL OF CHERRY LEAF-SPOT AND POWDERY MILDEW ON SOUR CHERRY WITH ALTERNATE-SIDE APPLICATIONS OF FENARIMOL, MYCLOBUTANIL, AND TEBUCONAZOLE

We evaluated spray programs for control of cherry leaf spot (caused by Blumeriella jaapii) during 1989-1991 in a sour cherry (Prunus cerasus) orchard in northern Michigan. Tebuconazole was as effective as chlorothalonil. Myclobutanil in combination with an adjuvant was next in effectiveness, followed by fenarimol and iprodione. Trees sprayed with the sterol demethylation inhibitor (DMI) fungicides fenarimol, myclobutanil, and tebuconazole also had a lower incidence of powdery mildew on the foliage than those sprayed with chlorothalonil or iprodione. Leaf spot control obtained with the DMI fungicides applied to alternate sides of sour cherry trees every 7 days was comparable to that obtained with sprays applied to both sides every 10 days, but 25% less fungicide was used in the alternate-side programs.