Aboveground Root Collar Excavation of Peach Trees for Armillaria Root Rot Management

Root collar excavation (RCE) has been applied to established citrus trees and grapevines for Armillaria root rot (ARR) control but, despite its demonstrated effectiveness, this cultural management system is not routinely used for ARR protection in disease-infested replant sites. One major drawback is the difficulty of excavating the belowground root collar, the potential of excavated roots to be covered again with surrounding soil, and the associated labor cost. In this study, a new cultural method was investigated that resulted in trees with aboveground excavated root collars, potentially eliminating many of the drawbacks. Experimental peach trees were planted in two commercial orchards (designated Landrum and Monetta) in South Carolina; each tree replaced one that had declined from ARR disease the year before. Trees were planted approximately 40 cm higher than normal in open-bottom Smart Pots and root collars were excavated above ground level 8 months later. Five years after planting, 30 and 70% of all control trees (planted according to grower standard) had declined from ARR disease in Landrum and Monetta, respectively, whereas only 0 and 10%, respectively, of trees in the aboveground root collar excavation (AGRCE) treatment had declined. The difference in disease pressure between the two locations could not be attributed to differences in nematode pressure. Nonexcavated trees in Smart Pots revealed significantly less tree decline (P ≤ 0.05) compared with the control but tree decline in both locations was greater compared with the AG-RCE treatment (P ≤ 0.05). Trees in the AG-RCE treatment were as vigorous as the controls but produced more root suckers. In this 'prototype' study, we demonstrate the potential of aboveground root collar excavation for ARR management. Its potential for commercial use is discussed.