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Title: MAINTENANCE OF CORKY RINGSPOT DISEASE IN CROP ROTATIONS BY THE PRESENCE OF WEEDS

Author
item Boydston, Rick
item MOJTAHEDI, HASSAN - WSU, PROSSER, WA
item SANTO, GERALD - WSU, PROSSER, WA
item CROSSLIN, JAMES - WSU, PROSSER, WA
item Thomas, Peter

Submitted to: Western Society of Weed Science Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2001
Publication Date: 3/1/2002
Citation: BOYDSTON, R.A., MOJTAHEDI, H., SANTO, G.S., CROSSLIN, J.M., THOMAS, P.E. MAINTENANCE OF CORKY RINGSPOT DISEASE IN CROP ROTATIONS BY THE PRESENCE OF WEEDS. PROCEEDINGS OF WESTERN SOCIETY OF WEED SCIENCE, 55:50, #101. 2002.

Interpretive Summary: Corky ringspot (CRS) disease has increased in the Columbia Basin of Washington in recent years, and more than 5,000 acres are now contaminated. CRS disease is caused by tobacco rattle virus (TRV) and transmitted by Paratrichodorus allius nematodes in the Columbia Basin. The disease is characterized by arcs, concentric rings or diffuse extensive browning of tuber flesh that later dries into cork-like tissue, making the affected crop unsaleable. Presently, the disease is controlled by Telone II fumigant (25 gal/A), which costs about $300/A and by Temik (aldicarb) placed in the seed furrow. Several standard rotation crops, such as, wheat and corn, are hosts of both the nematode vector and the virus. We have demonstrated in greenhouse experiments that TRV can be eliminated from soils by growing alfalfa or Scotch spearmint. Although these crops are good hosts of the nematode vector, the nematode cannot acquire the virus from them. P. allius molts four times in its life cycle, and loses its virus load after each molt. Thus, it must reacquire TRV from an infected host plant before it become viruliferous again. Weeds in alfalfa and spearmint may serve as hosts for TRV and the nematode vector and may allow the disease to persist in these crops. This research identified several weed species that are hosts of the virus and the nematode vector. Black and hairy nightshade are particularly good hosts. The presence of these weeds in alfalfa or spearmint may nullify the positive effects of cleansing the nematode of TRV while growing alfalfa or spearmint.

Technical Abstract: Corky ringspot disease (CRS) is a serious disease in potato that is caused by tobacco rattle virus (TRV). TRV is transmitted by the stubby root nematode (Paratrichodorus allius) in the Pacific Northwest potato producing regions. Alfalfa has been suggested as a rotation crop to eliminate the disease from the soil. Although alfalfa is a good host of P. allius, the nematode vector cannot acquire the virus from alfalfa. Viruliferous P. allius sheds the virus with each molt, and the population is cleansed after several generations on alfalfa. We have demonstrated similar results with 770 Scotch spearmint (Mentha cardiaca, Baker). However, weeds present in these rotation crops may serve as hosts for TRV and perpetuate the disease. This research determined the host status of over thirty common weed species for TRV and P. allius. black nightshade (Solanum nigrum), hairy nightshade (Solanum sarrachoides), prickly lettuce (Lactuca serriola), henbit (Lamium amplexicaule), common chickweed (Stellaria media), and kochia (Kochia scoparia) were found to be hosts of both TRV and P. allius. In greenhouse trials, prickly lettuce grown with alfalfa and green foxtail (Setaria viridis) grown with Scotch spearmint were infected with TRV using P. allius as a vector. After removing these plants, Russet Burbank potato was planted in the same soil and the residual population of P. allius in the pots previously harboring weeds and crop plants transmitted TRV to potato tubers and caused CRS. The nematodes present in pots previously planted to alfalfa or spearmint without weeds did not transmit TRV to cause CRS on potato. The presence of weeds that serve as hosts of both TRV and P. allius may nullify the positive effects of growing alfalfa and spearmint for CRS control. Targeted control efforts on these weeds may be required to successfully eliminate CRS from fields using crop rotation as a method to eliminate the disease.