Plant Disease Control Article from Oregon State University


The easiest way to control plant disease

By Judy Scott, 541-737-1386
Source: Jay Pscheidt, 541-737-3472Tomato  Blight

CORVALLIS. Ore.— Fall is a good time to look around at what flourished this year in the garden and yard and what succumbed to disease. You’ll save yourself heartache and money next year if you choose disease-resistant varieties.

“Planting resistant varieties is the easiest means of disease control,” according to Jay Pscheidt, plant pathologist with the Oregon State University Extension Service. “Roses, fruit trees and many vegetables such as tomatoes are susceptible to a variety of diseases caused by fungi and viruses. Choose those marked ‘disease resistant’ or ‘certified virus-free’ whenever possible.”

For example, tomato seed packages and start tags often are marked with the letters V, N, T or F. V signifies resistance to Verticillium, a fungal disease causing premature wilt and reduced production. N stands for a nematode-resistant variety. Nematodes are small wormlike pests that puncture root cells. T indicates resistance to tobacco mosaic virus, which causes mottled leaves. An F means the variety is resistant to Fusarium, another fungal disease that causes wilt.

Tomato varieties known to be resistant to all of these diseases include Carmen, Carnival, Casino Royal, Cavalier, Celebrity, First Lady, Milagro and President.

Other vegetables also have disease-resistant or disease-tolerant varieties, including green beans, peas, cucumbers, peppers and spinach.

The fungal diseases rust, powdery mildew and blackspot are common in rose gardens in the Pacific Northwest. Roses known to be resistant to these diseases include the hybrid teas Electron, Keepsake and Las Vegas; the floribundas Europeana, Liverpool Echo and Play Girl; and climbers Dortmund and Dublin Bay.

Apples are susceptible to several diseases including apple scab, fire blight and powdery mildew. Varieties that grow well, have shown good scab resistance and are of good quality include Akane (Tokyo Rose), Chehalis, Liberty, Prima and Tydeman Red.

Crab apples have the same problems, and Pscheidt recommends planting disease-resistant crab apple cultivars David, Indian Summer, Red Jewel or White Angel.

Consult catalogs and local nurseries for other disease-resistant varieties, as new ones come out each year and some of the old ones get discontinued.

For more information about disease resistance call the Master Gardener Program at your local county office of the OSU Extension Service. Online at

About Garden News from OSU Extension Service: The Extension Service’s “Gardening Encyclopedia” web page,, links to a broad spectrum of information on Oregon gardening, such as news, calendars, how-to publications, audio programs, the Master Gardener program and “Northwest Gardeners e-News.”

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