2019 ASHS Annual Conference

Armillaria root rot (ARR), also known as oak root rot, is currently one of the most threatening diseases affecting stone fruit in the U.S. This soil-borne fungal disease is a primary cause of premature tree decline particularly for peach (Prunus persica (L.)) in the Southeastern U.S. The causal fungus in the Southeast (Armillaria tabescens (syn. Clitocybe tabsecens)) spreads via root-to-root contact, infecting the root system and often killing the tree prior to its maximum productivity. Not uncommonly, trees of 3 and 4 years of age can succumb to the disease on infected replant sites. No proven long-term control strategies exist to eradicate the pathogen. As such, tree losses from ARR on formerly highly productive orchard sites have now reached uneconomical levels; approximately 40% of an orchard planted on an ARR-infected replant site is lost by the time it reaches 10 years of age. With a lack of virgin (i.e., non-replant) land available and no effective means to eradicate the pathogen, an immediate solution is required for the sustainable production of peach trees in the Southeast. Above ground root collar excavation (AGRCE) promises significantly longer tree survival on ARR-infected replant sites than grower standard plantings. In this cultural management system trees are planted on raised beds (berms) and root crowns are excavated after two growing seasons to uncover primary roots and expose the fungus to an inhospitable growing environment. To evaluate influence of the AGRCE planting system on tree survival and productivity, field trials were established in 2011 on ARR-infected replant sites on commercial (Ridge, SC) and research farms (Seneca, SC). Yield and fruit quality (brix, size and firmness), disease incidence and disease severity data were collected at each location from AGRCE orchards and compared to the grower standard plantings. The AGRCE field trials showed significantly lower tree mortality and no difference in yield and fruit quality when compared to grower standard. Even though peach trees eventually succumb to ARR, AGRCE provides an effective management approach to ensure sustainability of the peach industry in the Southeast.