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Management of Blackspot of Rose in the Landscape in Alabama. K. L. BOWEN, Department of Horticulture, Auburn University, Auburn, AL 36849. B. YOUNG, Department of Plant Pathology, and B. K. BEHE, Department of Horticulture, Auburn University, Auburn, AL 36849. Plant Dis. 79:250-253. Accepted for publication 9 December 1994. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0250.

Two application schedules for chlorothalonil, a solution of sodium bicarbonate and horticultural oil, and an untreated control, were assessed for effectiveness in the control of blackspot of rose during 1992 and 1993 in Alabama using a variety of ground covers. Weekly applications of chlorothalonil were superior to applications following 0.63 cm of rain for both years. Sodium bicarbonate solution reduced disease when inoculum levels were low, i.e., after initial establishment of rose beds, but were ineffective in the subsequent year when inoculum levels were higher. In 1992, less blackspot developed on plants with oat straw or pine straw ground covers than on those with landscape mat or bare soil. In 1993, lowest disease severity was observed on plants with oat straw ground cover. When disease levels were high, severity of blackspot was inversely correlated to flower production on each of three varieties.

Keyword(s): Diplocarpon rosae, mulch, pesticide alternatives, fungicides