Potato (Solanum tuberosum) -- Verticillium Wilt (Potato Early Dying)
Cause:
A fungus, Verticillium dahliae, which survives in soil or infected plant parts. It infects through roots and invades the plant's water-conducting tissues. Disease severity is proportionate to the inoculum density of the fungus in the soil. 'BelRus', 'Shepody', 'Russet Norkotah ', and 'Superior' are a few of many susceptible cultivars. 'Russet Burbank' is considered moderately resistant. 'Ranger Russet' is more resistant.
Symptoms:
Vines prematurely yellow and die. Early symptoms are characterized by unilateral leaf yellowing. Later, wilted and/or died plants stand upright. In cross section, particularly at or below the soil line, damage plants exhibit a darkened vascular system. This disease can greatly reduce yield from the onset of disease symptoms.
Note the wilted, chlorotic, dying leaves.
Vascular discoloration is associated with Verticillium wilt.
Note the tiny, dark microsclerotia produced by the fungus.
Sampling:
Send soil samples to any of various public and private labs throughout the Pacific Northwest to determine the number of Verticillium propagules per unit of soil.
Cultural
control:
Rotate with weed- and volunteer-free alfalfa or cereals.
Optimum rates of nitrogen fertilizer reduce symptoms' severity.
Irrigation management early in the growing season can help reduce disease severity. Keep soil water availability from 75 to 100% before tuber initiation.
Plant resistant cultivars.
In Idaho, green manure treatments of sudan grass or corn helped suppress disease.
Chemical
control: Soil fumigation gives economic control or suppression. Some labels call the disease "early maturity disease."
For control of Verticillium and Columbia root-knot nematode (Meloidogyne chitwoodi), or stubby-root nematode (Paratrichodurus spp.) as a vector of tobacco rattle virus (causal agent of corky ringspot disease), use metam sodium or metam potassium in combination with Telone II. See label for details.
Telone C-17 at 24 to 27.5 gal/A is registered for white potatoes. 5-day reentry. Restricted-use pesticide.
Apply a minimum of 38 (up to 75) gal/A of metam sodium 42% (Busan, Nemasol, Sectagon, Soil Prep, Vapam HL, etc.) through sprinkler irrigation systems in sufficient water to penetrate to the desired treatment depth. Meter continuously into the irrigation system throughout the entire application period. Soil temperature should be in the range of 40 to 90°F in the treatment zone. Soil moisture immediately prior to treatment must be 50 to 80% of field capacity down to the 24-inch level. Soil condition must facilitate even water penetration without runoff.
Metam sodium can also be injected into soil using shanks, blades, fertilizer wheels, plows, etc. Follow immediately with a roller/packer to smooth and compact the soil surface to help prevent escape of fumigant. See specimen label for specific uses, rates and application methods. For optimum control of Verticillium, injectors should be placed 4 to 6 inches below the soil surface and 5 to 6 inches apart. If nematodes are targeted, an additional injection at 12 inches (and perhaps an additional 18 inches) is necessary. Metam sodium may also be applied at the rate of 50 to 75 gal/A using a Noble Plow Blade set to 12 to 14 inches deep with spray nozzles spaced every 6 inches apart to give uniform coverage, plus a surface application using a disk to immediately incorporate the surface application. Reduced rates of metam sodium can be used when used in combination with Telone II. See label for details. 48-hr reentry.
Metam potassium (54%) can be used in a similar fashion to metam sodium at rates of 30 to 60 gal/A.
References: Powelson, ML. and Rowe, RC. 1994. Potato early dying: Causes and management tactics in the eastern and western United States. In: Zehnder, G.W. et al. 1994. Advances in Potato Pest Biology and Management. St. Paul, MN: APS Press.
Content edited by:
R. Ingham and C.M. Ocamb on
January 1, 2010
