Cause Xiphinema americanum and related species are vectors of Tomato ringspot virus (ToRSV). Xiphinema bakeri, another dagger nematode, has not been shown to transmit viruses. Dagger nematodes are migratory ectoparasites found only in soil. As virus vectors, they can be damaging at very low population levels. Dagger nematode populations are low in late summer when other nematodes are abundant. Highest populations are found during the winter and are correlated with rainfall. They only have one generation per year in western Washington. Transmission of the virus is suspected to occur in the early fall and spring when soil moisture and temperature are optimal for nematode activity. Transmission is slow and generally to adjacent plants; however, new foci can develop if soil, which contains nematodes, is moved within a field.
Symptoms Feeding by X. bakeri causes swellings and fishhook-like curling of the root tips. Stunting of the roots leads to reduced cane growth. The decline is similar to that described for plants attacked by the root-lesion nematode. In the absence of Tomato ringspot virus, X. americanum group nematodes cause little direct root damage.
Sampling Best sampling time for dagger nematodes is December to April. Take samples far enough ahead of planting to allow time to implement control tactics if necessary. Sample all potential planting sites. Divide large areas to be sampled into 5-acre blocks or less.
- Use certified planting stock.
- Plant in soil that has been tested and found free of dagger nematodes.
- If the nematode is detected, plant a shallow-rooted grass crop for 2 years. The shallow roots bring the nematodes to the upper portion of the soil profile, where they are more easily controlled with fumigants. Planting a non-host crop reduces virus inoculum because the nematodes cannot reacquire the virus.
- Remove infected plants and treat the soil with a fumigant to limit virus spread.
- Weed control is important since many broadleaf weeds (such as dandelion) are hosts for the nematode as well as the virus.
- Preplant soil fumigation the fall before spring planting is necessary to control dagger nematodes. Growing a shallow-rooted grass crop for 1 to 2 years will bring nematodes to upper soil levels where fumigation more easily controls them.
- Basamid G. Avoid application when soil is over 90°F. Do not apply within 3 to 4 feet of growing plants. Do not harvest within one year of application. 5-day reentry. Restricted-use pesticide.
- Telone II at 27 to 35 gal/A broadcast on mineral soils. 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.
- Vapam HL at 37.5 to 75 gal/A. Immediately after application roll the soil and follow up with tarps or a light watering. May apply through an irrigation system. 5-day reentry Restricted-use pesticide.
- Velum Prime at 6.5 to 6.84 fl oz/A can be used after planting using drip, trickle of micro-sprinklers. Can be applied day of harvest. Group 7 fungicide. 12-hr reentry.
- Vydate L at 2 quarts/A can be used after planting on non-bearing plants. Apply 0.25 to 0.5 inches water (or rainfall) to wet the top 2 inches of soil after application. For western Washington only SLN WA-120005. 48-hr reentry. Restricted-use pesticide.
Note Some registered products offer only suppression of this disease and thus are not recommended for use. These products include Majestene.
Reference Pinkerton, J.N., Kraus, J., Martin, R.R., and Schreiner, R.P. 2008. Epidemiology of Xiphinema americanum and Tomato ringspot virus on red raspberry, Rubus idaeus. Plant Disease 92:364-371.