Pacific Northwest 1998 An Online Guide to Plant Disease Control

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OSU Extension Office
 
Grape -- Nematode (Root-knot)
 
Cause: Meloidogyne hapla (northern root-knot nematode), a sedentary endoparasite (see Nematodes), and only second-stage juveniles (the infective stage) and adult males (which may be rare) are present in soil. Spread to new areas usually is due to planting infected, rooted plants or moving infested soil. Root-knot nematode was found in 10% of the Oregon vineyards surveyed and in 66% of Washington vineyards. In eastern Washington, root-knot nematodes may be more problematic in vineyards planted on sites previously cropped to potato or alfalfa.
Symptoms: Small distinct galls on roots; poor growth; shortened lifespan of the vine; reduced yield. Affected plants generally are in circular or oval areas in the field. Other problems, such as Armillaria root rot or phylloxera, can cause a similar damage pattern.
Sampling: Take soil samples well before planting to implement management procedures if necessary. It may be several weeks before crops can be planted after soil fumigation. Fall sampling for crops to be planted the following spring is an excellent strategy.

The best time to sample is at the end of the growing season when populations are highest. Take samples 1 ft from the vine and in the vine row. Remove the top 2 to 3 inches of soil and sample 1 ft deep with a 1 inch diameter soil tube. Take 10 to 20 sub-samples in a given area and combine into one sample. Include roots as well as soil. Yield loss in eastern Washington has been associated with population densities around 200 to 300 per 250 cc soil.

Cultural control:

  1. Use clean root stock.
Chemical control: The key in managing nematodes on perennial crops such as grape is to protect new roots from nematode feeding. This allows roots to establish to the point that they can tolerate nematode feeding after the chemical's effects dissipate.

  1. Preplant fumigation.
    1. 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. 24-hr reentry plus ventilation.
    2. Metam sodium products such as Vapam. 48-hr reentry.
    3. Telone II up to 55 gal/A in mineral soils. Soil conditions where grapes are grown are often not conducive for optimum performance of this fumigant. Check label for proper ground preparation before application. 5 day reentry. Restriced Use Pesticide.
  2. Enzone can be used through low volume irrigation systems. Use 5 to 30 gal/A/treatment for established vineyards or 20 to 60 gal/A/treatment before planting. Soil temperature must be above 58°F at 6 inches and plants must be established for at least 1 year before treatment. Several applications to an existing vineyard are recommended on the label. Do not apply within 2 weeks of harvest. Oregon and Washington only. 4-day reentry.
Content edited by: John Pinkerton and Jay W. Pscheidt on January 1, 2009
 
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