EFFECTS OF MANAGEMENT-PRACTICES AND FUNGICIDES ON SOOTY BLOTCH AND FLYSPECK DISEASES AND PRODUCTIVITY OF LIBERTY APPLES

Effects of tree spacing, ground cover management, and summer fungicide s on the incidence and economic impacts of sooty blotch and flyspeck ( SBFS) were evaluated over four seasons in a high-density planting of L iberty apples by determining disease incidence, number of fruit produc ed, total yield, pack-out, and potential gross returns for each treatm ent. Tree spacing and ground cover management had no effect on the inc idence of SBFS on fruit in the upper tree canopy Disease incidence on fruit from the lower tree canopy was unaffected by tree spacing but wa s reduced slightly by careful ground cover management. Fungicides appl ied during summer consistently reduced the incidence of SBFS in both t he upper and lower canopy area. Sprayed trees defoliated approximately 2 weeks later in October than unsprayed trees each year. Return bloom was not affected by fungicide treatment, but fruit-set efficiency, nu mber of fruit produced, total harvested yield, and estimated gross ret urn per ha were higher in the plots receiving fungicides than in those receiving no fungicides. Plots treated with fungicides had 11.6% grea ter mean yield and 50% greater gross returns than untreated plots. Pos sible reasons for the premature defoliation and reduced fruit set on t rees receiving no fungicides are discussed.