A STRATEGY FOR REDUCING RUSSET IN RED FUJI APPLES WHILE MAINTAINING CONTROL OF BLACK SPOT (VENTURIA-INAEQUALIS)

A trial at the Grove Research Station in southern Tasmania examined me thods of protection against black spot and the effect of these treatme nts on russeting of Red Fuji apples. An untreated control was compared with sprays of cupric hydroxide (wettable powder and dry flowable for ms, 2.5 g/L) and copper oxychloride (4.0 g/L), and with dithianon (wet table powder 5 g/L, or suspension concentrate 5.0 or 7.5 g/L). All spr ays were applied at greentip, and dithianon was also applied at 10-day intervals for 5 sprays (spring program). Copper treatments were follo wed, or not, by a spring program of thiram, and all treatments were wi th or without a following summer program of thiram. Control of black s pot (95% fruit with no spot) was not achieved with copper sprays at gr eentip alone, although control was better than on the unsprayed treatm ent. All dithianon programs, and cupric hydroxide sprays followed by t hiram, controlled black spot. No difference was found between formulat ions for either cupric hydroxide or dithianon. Copper oxychloride incr eased the incidence of severe russet to >50% compared with the unspray ed control (28.5%). All other treatments were satisfactory, with simil ar incidence of russet to the control treatment, and could be used in commercial practices.