In general, trees suffering from replant disease show slow and uneven growth within the first three years of planting (A). Both specific (e.g., apple after apple) and non-specific (e.g., stone fruit after vegetables) replant disorders are known. The disorder is characterized by reduced shoot growth, severe stunting, rosetted leaves, and reduced fruit production. The root systems of affected trees are fibrous, poorly developed and are often in a state of decay.
Common to all fruit-growing regions in eastern North America.
A number of organisms and pathogens have been associated with replant disease including fungi in the genus Cylindrocarpon, Phytophthora cactorum (Lebert & Cohn) J. Schröt., Phytophthora spp., Pythium spp., and Rhizoctonia solania Kühn, and nematodes including the lesion nematode [Pratylenchus penetrans (Cobb) Filipjev & Schuur.-Stek.], root-knot nematodes (Meloidogyne spp.), ring nematodes (Criconemella spp.) and sometimes dagger nematodes (Xiphinema spp.). The consensus is that replant is caused by a complex of organisms, thus symptoms of this disease are varied and no truly diagnostic symptom distinguishes replant disease from other maladies that cause decline or poor growth.
In replant sites, soils should be tested for known causal organisms (if possible) and for pH; low pH is known to exacerbate the disease. Cultural methods that reduce replant disease include planting new trees in the drive alley or digging holes the autumn prior to planting to expose the causal organisms to harsh conditions. Pre-plant soil fumigation, particularly with methyl bromide, metam sodium, or chloropicrin, is often effective in minimizing losses due to replant disease.
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