Cause Pratylenchus penetrans, P. thornei and P. neglectus have been found in established blueberry fields. Root-lesion nematodes are migratory endoparasites with part of the population in soil and part in the roots at all times. Blueberry is not considered a host for these species, which are likely surviving on weed hosts.
The root-lesion nematode species of concern in the Pacific Northwest is Pratylenchus crenatus. The impact that this nematode has on blueberry establishment and productivity has not been determined.
Symptoms A nonspecific decline with poor growth and yellowish foliage are the most likely symptoms. Diagnosis is possible only by comparing nematode densities in root and soil samples of sick and healthy plants.
Sampling If plants are present, always include both soil and roots in samples sent for nematode analysis. Take samples any time if the numbers are interpreted in relation to nematode population dynamics. In most crops, populations are relatively low through winter and spring but increase rapidly through summer. July and August are good times to sample for these nematodes in blueberries and in fields that will be planted to blueberries.
Cultural control
- Plant in fields with low population densities.
- Fallow the year prior to planting. Diligently control broadleaf weeds during the fallow year to eliminate possible hosts.
- Remove diseased plants and fumigate infested area.
Chemical control At this time there are no products with proven postplant efficacy registered for use on blueberry. Preplant assessment of nematode levels is necessary to determine if preplant fumigation is required.
- 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 on mineral soils in the fall before spring planting. Leave the soil undisturbed for at least 7 days after application. A longer interval, such as 2-3 weeks, is required if soils are cold or wet, or the site will be replanted with deep rooted trees, shrubs or vines. Odor indicates fumigant presence; do not plant until odor leaves the soil. Do not treat extremely heavy soils. 5-day reentry. Restricted-use pesticide.
Biological control
- 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
Reference Zasada, I.A., Pinkerton, J.N. and Forge, T.A. 2010. Plant-parasitic nematodes associated with highbush blueberries (Vaccinium corymbosum) in the Pacific Northwest of North America. International Journal of Fruit Science 10:123-133.