Armillaria root rot

ARR_rootOne of the greatest threats to stone fruit orchard sustainability in the Southeast is Armillaria root rot caused by the basidiomycete fungus Armillaria (right: mycelium in roots). For example, in South Carolina between 1987 and 1992, the disease was estimated to have caused $3.86 million in annual losses, and in Georgia from 2000 to 2002 Armillaria root rot, including control costs, resulted in more than $1.5 million in losses to the peach industry. In addition to direct monetary losses, persistence of the pathogen in the soil on infested residual root pieces prevents the establishment of productive orchards in previously infested sites, thereby causing additional loss of income. 

Historically, Armillaria has been the second leading contributor of premature peach tree mortality after peach tree short life (PTSL). In recent years, however, Armillaria root rot has become the primary cause of premature tree mortality in the region, caused in part from the decline of PTSL incidence due to the widespread availability of PTSL-tolerant rootstocks such as Guardian; Indeed, the Georgia and South Carolina crop profile for peach, a part of the national Pest Management Strategic Plan website, affirms that Armillaria is a primary cause of premature orchard decline and mortality in the Southeastern United States. Regional stakeholder groups are also concerned about Armillaria root rot. Despite the increased concern, the prevalence of the disease will only become worse in South Carolina and Georgia as producers are often forced to replant in former peach sites or cleared forest land with endemic Armillaria populations.

ARR_mushroomsAlthough scientists have been researching this pathogen (left: A. mellea mushrooms) since the beginning of the 20th century, little progress has been made in developing effective control strategies. Currently, the only practical control measure is to avoid planting on land infested with Armillaria. Since suitable land for peach production is often unaffordable or unavailable due to increased urbanization, replanting on non-infested land is often not an option for stone fruit growers. We are in need for an integrated management program to prevent the rapid, often devastating tree mortality occurring in Armillaria infested orchards.

Our goal is to develop an integrated approach for Armillaria root rot management based on the following components:

    * Cultural ARR management - Root Collar Excavation
    * Biological control - Trichoderma
    * Targeted chemical management - Trunk Infusion
    * Resistant rootstocks