By K. Frost and C. M. Ocamb
Cause Tobacco rattle virus (TRV) is transmitted by the soilborne nematodes, Trichodorus spp. and Paratrichodorus spp. The presence of TRV, coincident with its nematode vector, is widely scattered in the Pacific Northwest and the resulting disease can cause extensive damage. Corky ringspot has been more severe when potatoes follow mint. All currently grown varieties can be infected by TRV but there is variation in the incidence and severity of tuber necrosis among varieties infected with TRV.
Symptoms There usually is no apparent foliage symptom under field conditions. Internal symptoms are generally necrotic arcs or brown spots but larger necrotic areas can sometimes be seen. Tuber symptoms caused by TRV can be confused with symptoms caused by Potato Mop-Top virus and Potato virus Y. Arcs on the surface of tubers can be sometimes seen in smooth skin varieties.
- Do not plant potatoes in fields with a known corky ringspot history without proper chemical control of nematode vectors. Fields with unknown history should be sampled for the presence of the nematode (stubby root) and then assayed for the virus. Failure to adequately control this disease can result in complete loss.
- Control nightshade, pigweed, and purslane while rotating out of potatoes to reduce the virus reservoir.
Chemical control Control of the nematode vector is mandatory if the field has a history of the disease.
- Use Telone II as a preplant fumigant at recommended rates. Restricted-use pesticide.
- Vydate C-LV at recommended rates at planting and on recommended intervals during the crop season will suppress nematode populations. Restricted-use pesticide.