Evaluation of chemical, genetic and biological control strategies for Armillaria root rot of peach

Armillaria root rot (ARR), incited by Armillaria tabescens (Desarmillaria tabescens), is a major soil-borne disease in many stone fruit production areas worldwide. Following the release of Guardian peach rootstock in 1993 to address the then primary issue of peach tree short life, ARR has become the most important cause of premature tree mortality in the southeastern US peach industry. Attempts to eradicate the fungus via either chemical fumigants or cultural management practices, such as root removal or fallowing, have rarely achieved measureable success. The purpose of this trial was to compare three pre-plant chemical fumigants, genetic resistance (plum vs. peach rootstock) and a biological control agent (Trichoderma harzianum) either alone or in combination with each other as possible controls. The trial was conducted on a peach site with a known history of ARR utilizing a split-split plot design with fumigation treatment (methyl bromide, methyl iodide, Telone-C35 or unfumigated) as the main plot, rootstock treatment (a plum selection vs. Nemaguard peach seedling) as the split plot and biocontrol treatment (T. harzianum applied for the first 3 years vs. water check) as the split-split plot. Entering the 15th growing season only genetic resistance, i.e. the plum rootstock selection, provided any significant suppression of tree losses due to ARR.