- The disease may be caused by two species of fungi:
- Verticillium albo-atrum
- Verticillium dahliae
- Verticillium wilt may reduce tuber yield by as much as 70 %. More …
- Verticillium wilt may occur in crops showing patches of early senescence.
- Propagules may occur in soil as microsclerotia of V. dahliae or resting mycelium of V. albo-atrum.
- Propagules may be moved within fields or between fields by:
- soil on machinery
- blowing dust
- irrigation water
- Propagules may be introduced in soil on seed tubers but mycelium within infected seed tubers is considered to be of relatively minor importance.
- Propagules may remain viable for several years.
Symptoms of Verticillium wilt
- Verticillium infects through the roots, hyphae grow into the vascular system and leaf area of infected stems may be restricted.
- As the disease develops, lower leaves wilt, become chlorotic and finally necrotic. Symptoms progress up the stem until the stem becomes desiccated and dies.
- One or more stems on a plant may be infected while other stems on the same plant show no symptoms.
- Symptoms may occur on only one side of a stem or leaf.
- If infected stems are peeled or cut at a sharp angle at ground level, tan or light brown coloration of the xylem may be seen.
- Severe infection may result in premature crop senescence.
- Tubers on infected plants may show signs of vascular browning.
- The symptoms may be confused with those of the following diseases, which may also be confused with each other:
- stem canker (Rhizoctonia)
- Fusarium wilt
- pink rot (Phytophthora erythroseptica)
- black leg (Pectobacterium)
- ring rot (Cornynebacterium)
- brown rot (Ralstonia solanacearum)
- Positive identification may require isolation of the fungus.
- Agricultural and horticultural crops including:
- Weeds including:
- Chenopodium album
- Capsella bursa-pastoris
- Taraxacum spp.
- Equisetum arvense
- Many species of trees.
- Non-susceptible crops include:
- It is often suggested that Verticillium wilt is exacerbated by nematode infection (free-living and potato cyst nematodes).
Soil test for Verticillium
- There is a test for V. dahliae available which was developed for the strawberry industry and is performed by FERA.
- A 2 kg soil sample, comprising 50 sub-samples, should be taken with uniform distribution from an area of 1 ha.
- There is circumstantial evidence that crops may be at risk of early senescence if soil contains > 4 propagules / g soil.
Control of Verticillium
- Experiments with soil applied chemicals have resulted in only small reductions in infection. More …
- Plants which are infected with Verticillium may be more susceptible to black dot.
- Application of azoxystrobin (“Amistar”) to soil has been shown to reduce black dot while having little affect on Verticillium infection.
- Other experiments have shown some reductions in Verticillium after soil amendment with organic materials. More … and more …
- Flaming of potato haulm has also been shown to result in some reductions in Verticillium populations.
- Long rotations with non-host crops and good control of weeds can help to minimise build up of Verticillium in soil.
Verticillium wilt notes
Verticillium wilt 2017 (Symptoms; biology; alternative hosts; influence of soil conditions; soil test)
Verticillium wilt 2005 (Population change during crop growth; experiments on chemical applications to soil)
Verticillium wilt 2001 (Verticillium species; yield loss; effects of soil amendments)