MANAGEMENT OF BLACKSPOT OF ROSE IN THE LANDSCAPE IN ALABAMA

Two application schedules for chlorothalonil, a solution of sodium bic arbonate and horticultural oil, and an untreated control, were assesse d for effectiveness in the control of blackspot of rose during 1992 an d 1993 in Alabama using a variety of ground covers. Weekly application s 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 b eds, but were ineffective in the subsequent year when inoculum levels were higher. In 1992, less blackspot developed on plants with oat stra w or pine straw ground covers than on those with landscape mat or bare soil. In 1993, lowest disease severity was observed on plants with oa t straw ground cover. When disease levels were high, severity of black spot was inversely correlated to flower production on each of three va rieties.