Cause Mesocriconema spp., ring nematodes, are ectoparasites and may feed several days at a single site. They predispose trees to other pathogens such as bacterial canker and to environmental stresses.
Symptoms Heavy feeding results in the feeder roots' death. Fine roots that remain are necrotic or grouped in short clusters. The tree's shoot or root growth may be reduced.
- Avoid sites with high soil populations of ring nematodes.
- Preplanting the future orchard site with winter wheat followed by fallow have helped reduce populations.
- Preplant soil 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.
- Dominus at 10 to 40 gal/A. Apply as a shank injection to an entire field or raised beds when soil temperatures are above 60°F but not greater than 90°F. 5-day reentry.
- Telone II at 27 to 35 gal/A broadcast or 24 fl oz/single tree planting site delivered 5 ft deep. 5-day reentry. Restricted-use pesticide.
- Ecozin Plus at 25 to 56 oz/A is registered for use after planting through a drip irrigation system. Label suggests using additives to aid penetration into the soil and to make applications in the morning. Efficacy in the Pacific Northwest is unknown. 4-hr reentry. O
- MeloCon WG (Paecilomyces lilacinus strain 251) at 2 to 4 lb/A plus a soil wetting agent can be applied to established plants, although it might be better used when applied to plants just before planting. Stable for only days at room temperature, weeks in the refrigerator or for a year if frozen. Unknown efficacy in the PNW. 4-hr reentry. O
Note Some registered products offer only suppression of this disease and thus are not recommended for use. These products include Velum Prime.
References Nyczepir, A.P., Bertrand, P.F., and Cunfer, B.M. 1996. Suitability of a wheat-sorghum, double crop rotation to manage Criconemella xenoplax in peach production. Plant Disease. 80:629-632.
Ogawa, J.M., Zehr, E.I., Bird, G.W., Ritchie, D.F., Uriu, K., and Uyemoto, J.K. 1995. Compendium of Stone Fruit Diseases. St. Paul, MN: APS Press.