Cause Beet western yellows virus, an increasingly significant pathogen in western Oregon. The principal vector is the green peach aphid, Myzus persicae; other aphid vectors are likely. After acquiring the virus from infected plants, aphids may have lifelong ability to transmit it. An enormous number of crop and weed species are susceptible to this virus and act as natural inoculum reservoirs. Crops commonly infected in western Oregon include beets (table and sugar), broccoli, most clover species, mustard, lettuce, pea, radish, spinach, Swiss chard, and turnip. Weeds commonly infected in western Oregon include burdock, Canada thistle, cutleaf geranium, dog fennel, groundsel, pigweed, redstem filaree, weedy clovers, and wild mustard.
Symptoms Leaves yellow prematurely, typically first at the margins and progressing in; veins and midribs tend to stay green. Oldest leaves tend to yellow first. Yellow symptoms progress up the plant, which results in reduced and abnormal growth that is unmarketable.
Cultural control The disease is very difficult to control due to the wide host range. Attempts are under way to identify varieties and breeding lines that are both suitable to the Pacific Northwest and resistant to the virus.
- Separate new plantings from infected crops by as much space and time as feasible.
Reference Hampton, R.O., Keller, K.E., and Baggett, J.R. 1998. Beet western yellows luteovirus in western Oregon. Plant Disease: 82:140-148.