Effects of Management Practices and Fungicides on Sooty Blotch and Flyspeck Diseases and Productivity of 'Liberty' Apples

Abstract

Effects of tree spacing, ground cover management, and summer fungicides on the incidence and economic impacts of sooty blotch and flyspeck (SBFS) were evaluated over four seasons in a high-density planting of Liberty apples by determining disease incidence, number of fruit produced, total yield, pack-out, and potential gross returns for each treatment. Tree spacing and ground cover management had no effect on the incidence of SBFS on fruit in the upper tree canopy. Disease incidence on fruit from the lower tree canopy was unaffected by tree spacing but was reduced slightly by careful ground cover management. Fungicides applied during summer consistently reduced the incidence of SBFS in both the 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, number of fruit produced, total harvested yield, and estimated gross return per ha were higher in the plots receiving fungicides than in those receiving no fungicides. Plots treated with fungicides had 11.6% greater mean yield and 50% greater gross returns than untreated plots. Possible reasons for the premature defoliation and reduced fruit set on trees receiving no fungicides are discussed.