Cause Xiphinema americanum and related species. Xiphinema americanum is the vector for Tobacco ringspot virus and Tomato ringspot virus. Dagger nematodes are migratory ectoparasites and therefore found only in soil. As virus vectors, they can be damaging at very low population levels. Dagger nematode populations may be very low in late summer when other nematodes are abundant. Surveys have only found this nematode associated with blueberry fields in southern Washington and the Willamette Valley of Oregon.
Symptoms Dagger nematodes cause little direct root damage to plants unless they are present in high numbers. More important are the viruses they transmit that cause significant damage.
Sampling December through March is the best time to sample for dagger nematodes in established blueberry fields. If planting new fields, take samples during this period to increase the probability of detecting this nematode. The best way to collect soil samples is with a soil probe inserted to a depth of 12-18 inches. Remove the top few inches of mulch before putting the subsample into the bucket. Each probe-full of soil constitutes one subsample. Collect at least 20 to 30 subsamples for every 1 to 4 acres. Fields larger than four acres should be divided into sections, with separate nematode samples taken from each section. The subsamples should be drawn from sites chosen randomly throughout the field, usually by walking in a "W" pattern, and then mixed together in a clean bucket. Areas with different soil types or cropping histories should be sampled separately.
- Locate plantings on soil that has been tested and found free of dagger nematodes.
- Cover crop with tall fescue or rapeseed in the year(s) prior to planting.
- Fallow the year prior to planting. Diligently control broadleaf weeds during the fallow year to eliminate possible hosts.
- Plant virus-tested (and found to be free of all known viruses) certified stock.
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.
- Paladin at 35 to 51.3 gal/A. Buffer zone from 35 to 690 feet depending on the rate used and acreage treated. 2- to 5-day entry-restriction period. See label for details. Unknown efficacy in the PNW. Restricted-use pesticide, Washington only.
- Telone II at 27 to 35 gal/A broadcast on mineral soils in the fall before spring planting. Allow 2 to 3 weeks between treating and planting, or wait until odor has left the soil. Do not treat extremely heavy soils. 5-day reentry. Restricted-use pesticide.
References Pinkerton, J.N., Martin, R.R. 2005. Management of tomato ringspot virus in red raspberry with crop rotation. Int. J. Fruit Sci. 5:55-67.
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.