Apple (Malus spp.) - Replant Disease
Cause A complex of biological and environmental factors that varies by geographic region. Although more research has been done on apple replant disease, cherry replant disease is considered to be very similar in its overall epidemiology. Contributing factors in cherry replant disease include Pratylenchus penetrans (root-lesion nematode), inadequate soil or orchard management, and winter injury. Additionally, Cytospora canker, Mesocriconema sp. (ring nematode), and Pseudomonas syringae (bacterial canker) are typically associated with Peach Tree Shortlife and may be also be factors. Limited evidence also suggests that cherry replant disease may also occur when planting back into old pome fruit orchards. The role of soil microbial pathogens in cherry replant disease remains unknown. However, studies of apple replant disease suggest that oomycetes, Rhizoctonia, and Ilyonectria may be involved.
Replant disease affected orchards often have acid soils below pH 6.5. Acidic soil can reduce the availability of certain soil mineral nutrients, such as calcium, magnesium and phosphorous, while making metals, like aluminum and iron, more available. This can lead to nutrient deficiencies or heavy-metal toxicities that reduce overall plant growth and health. In addition, acidic soil conditions favor the growth and colonization of fungi, oomycetes, and pathogenic bacteria that are associated with apple replant disease, while inhibiting the growth of beneficial bacteria and mycorrhizal fungi.
Compacted soils from repeated tractor and implement use have greater bulk densities and reduced pore space, which can restrict root growth, reduce accessibility of nutrients by roots, reduce soil drainage and aerations, and decrease soil nutrient transformations. Compaction in heavy clay soils can drastically restrict root growth and cause "wet feet". Compacted soil with low oxygen will favor soil pathogens, like oomycetes.
Symptoms Replant disease has no definite symptoms other than poor tree growth the first few years after transplanting. Vigorous young trees planted in a problem site stop growing in early summer. Affected trees leaf out each spring but produce little or no shoot growth. Few new lateral or feeder roots are produced, and existing roots discolor and deteriorate.
- Avoid by not planting Prunus sp. on ground where old Prunus or pome fruit orchards have recently been removed. Rotations of 5 to 8 years are recommended in the absence of other tactics.
- Correct soil physical characteristics that are detrimental to growing cherry trees. Adjust soil pH to 6.5 to 7 using agricultural lime and adding organic matter, such as mulch or compost, to improve the buffering capacity of the soil.
- Plant a non-woody cover crop for 3-5 years before planting a new orchard can reduce disease pressure. Mixtures of brassicas, grasses and/or legumes are the most commonly planted cover crops but may require irrigation, especially during establishment in dry areas, and fertilizer applications. Use of a summer rotation with 'Piper' sudangrass was helpful in California but not as good as fumigation.
- Anaerobic Soil Disinfestation may be helpful even in the PNW. Rice bran is incorporated into the soil followed by irrigated to near field capacity. Then place clear oxygen impermeable plastic (such as anti-condensation film) on the prepared ground. Use in combination with other techniques.
Chemical control Preplant fumigation. Consult or hire a professional applicator to be sure it is done safely and effectively.
- Basamid G. Avoid application when soil is over 90°F. Do not apply within 3 to 4 feet of growing plants or closer than the drip line of larger plants. Do not harvest within one year of application. 5-day reentry. Restricted-use pesticide.
- Metam-sodium products such as Metam CLR (42%), Sectagon 42 or Vapam HL. Vapam HL can be used at 56 to 75 gal/A. Use in enough water to penetrate only 3 ft. or 6 ft for individual tree treatment. Remove as much tree root debris as possible before application. Trees adjacent to the treatment site may be injured. 48-hr reentry. Restricted-use pesticide.
- Telone C-17 at 32.4 to 42 gal/A depending on soil type and depth of penetration. 5-day reentry. Restricted-use pesticide.
References Browne, G.T., Lampinen, B.D., Holtz, B.A., Doll, D.A., Upadhyaya, S.K., Schmidt, L.S., Bhat, R.G., Udompetaikul, V., Coates, R.W., Hanson, B.D., Klonsky, K.M., Gao, S., Wang, E., Gills, M., Gerik, J.S., and Johnson, R.S. 2013. Managing the almond and stone fruit replant disease complex with less soil fumigant. California Agriculture 67:128-138.
Browne, G., Ott, N., Poret-Peterson, A., Gouran, H., and Lampinen, B. 2018. Efficacy of anaerobic soil disinfestation for control of Prunus replant disease. Plant Disease 102:209-219.
Melakeberhan, H., Jones, A.L., Sobiczewski, P., and Bird, G.W. 1993. Factors associated with decline of sweet cherry trees in Michigan: Nematodes, bacterial canker, nutrition, soil pH, and winter injury. Plant Disease 77:266-271.