Verticillium Wilt

Pathogen:Verticillium dahliae

Symptoms

The disease causes stunting, wilting, early senescence and total plant death. There is chlorosis on one side of the leaf between the main veins, which develops into necrosis at the edges, causing the leaf to die. Occurrence is usually noticed on one side of the plant. Brown discoloration becomes apparent in the vascular bundles of the stem and tubers. Small dark sclerotia are formed on desiccated stems and roots.

Damage

A considerable decrease in yield, but without damage to visual quality. Seed tubers carry the pathogen in their vascular bundles and can transmit the disease. Infested potato plants that have dried out infest the soil with micro-sclerotia, which can survive for long periods (10-14 years).

Conditions for Development

The fungus penetrates through plant roots, becomes established in the vascular bundles, and spreads systemically. Disease severity can be enhanced by the presence of free nematodes (Pratylenchus) in the soil or of Erwinia (the pathogen responsible for black foot disease) in the mother tubers, or by irrigating with saline water. The disease is most severe during autumn-winter.

Control

Varieties: Tolerant varieties exist.

Pesticides: Soil fumigation with high concentrations of metham-sodium or methyl-bromide eradicates the fungus. Treatment with low dosages of nematicides can also be partially effective.

Management: Use of disease-free seed tubers; crop rotation; use of disease-free manure.

Aerial Stem Rot
Black Dot, Colletotrichum coccodes
Blackleg and Tuber Soft Rot
Black Scurf, Rhizoctonia Canker
Common Scab, Streptomyces scabies
Early Blight, Alternaria solani
Deep Pitted Scab, Streptomyces spp
Leak, Pythium ultimum
PLRV, Potato Leafroll Virus
Powdery Scab, Spongospora subterranea
PVX, Potato Virus X
PVY, Potato Virus Y
Verticillium Wilt, Verticillium dahliae