Verticillium wilt is one of the most destructive fungal diseases affecting potato crops worldwide. This soil-borne disease can lead to significant yield losses if left unchecked. In this article, we’ll explore the symptoms, treatment, and prevention of Verticillium wilt in potato plants, along with pictures to help identify this problematic disease.
What Causes Verticillium Wilt in Potatoes?
Verticillium wilt is caused by two species of fungi – Verticillium dahliae and Verticillium albo-atrum These fungi can survive in the soil for many years through structures called microsclerotia When potato plants are infected by Verticillium fungi, the pathogens colonize the water-conducting tissues (xylem) of the plant. This blocks the movement of water and nutrients, causing the characteristic wilt symptoms.
The disease is spread by contaminated soil, infected seed tubers, and water used for irrigation. Verticillium is very hard to get rid of completely once it has spread to a field. Verticillium wilt tends to grow best in cool, wet conditions.
Recognizing Verticillium Wilt Symptoms
Identifying Verticillium wilt accurately is crucial for effective management. Here are some of the most common aboveground symptoms:
- Wilting and drooping of leaves and stems, especially during the hottest part of the day. Plants recover at night initially.
- Chlorosis (yellowing) of the lower leaves, progressing up the plant
- Early senescence and dying off of foliage.
- Stunted growth and smaller plants compared to healthy ones.
- Brown discoloration of the vascular tissue when stems are cut.
On potatoes specifically, symptoms include:
- Brown discoloration of the vascular ring when tubers are cut in half.
- Dark lesions on stolons and stems near the soil line.
- Premature death of haulms.
- Reduced tuber size and number.
Verticillium Wilt Pictures: Identifying Symptoms Visually
Here are some pictures illustrating the typical symptoms of Verticillium wilt on potato plants:
Wilted potato plant foliage
Wilting foliage is a classic symptom of Verticillium wilt. Bugwood picture by Mary Ann Hansen, Virginia Polytechnic Institute and State University org.
Lower leaf yellowing spreading up the plant Image by T. David Reed, North Carolina State University, Bugwoodorg.
Potato stem vascular discoloration
Brown vascular discoloration when stems are cut. Image by T. David Reed, North Carolina State University, Bugwood.org.
Vascular discoloration and lesions on infected tubers. Image by T. David Reed, North Carolina State University, Bugwood.org.
Treating and Preventing Verticillium Wilt
Once Verticillium wilt takes hold, there are no chemical treatments available to cure affected plants. The focus should be on preventive measures to avoid infection and spread of the disease. Here are some key tactics:
- Plant certified disease-free seed potatoes. Avoid saving your own tubers for seed.
- Practice long crop rotations, avoiding potatoes or other susceptible crops in the same field for at least 3-4 years.
- Control weeds, volunteers, and alternate hosts that can harbor the Verticillium fungi.
- Solarize soil or use other methods to reduce pathogen populations before planting.
- Maintain proper soil fertility and avoid excessive nitrogen.
- Water carefully to avoid stressing plants.
- Remove and destroy severely infected potato plants.
- Disinfect equipment regularly to prevent spreading the disease between fields.
Outlook for Verticillium Wilt Management
Verticillium wilt is hard to completely get rid of once it’s in a field, but proactive management can lessen the damage it does to potato yields. Key things are careful monitoring for early symptoms and doing things to avoid getting them.
Promising future methods may include developing potato varieties with genetic resistance to Verticillium, soil amendments to suppress the fungi, and novel biocontrol agents. Integrated pest management will be crucial to ensure potato productivity and profitability in the face of this persistent disease threat.
Verticillium wilt is a challenging potato disease, but its impacts can be minimized through vigilant monitoring, accurate diagnosis, and proactive management tactics. Avoiding the introduction of Verticillium fungi is vital. Once present, techniques like extended rotations and soil treatments can help reduce inoculum levels. Early symptom identification coupled with prompt removal of infected plants is critical. By combining preventive cultural practices, data-driven monitoring, and biotechnology solutions, potato growers can effectively manage Verticillium wilt.
Latent and mild mosaic viruses
The symptoms on the leaves of these plants range from none (latent) to very weak to a strong mosaic pattern with some leaflet distortion.
These viruses have an important economic impact since they affect yield and quality.
Latent crop infections provide a reservoir of inoculum that may infect adjacent crops.
Pink rot can be devastating, especially in hot dry years. Tubers may appear sound at loading but breakdown can begin in a matter of weeks.
Externally the infection front has a dark edge but this is not the case on the internal cut surface. Initially the affected flesh might appear more white or light grey than the natural flesh tone but within an hour the cut surface can turn pink and later dark brown to black.
Advanced infections lead to complete tuber breakdown and secondary infections.
Potato Virus Y (PVY)
Symptoms range from mild mosaic to severe foliar necrosis to plant death, depending on the virus strain and type of potato.
The most obvious tuber symptom associated with potato viruses is Potato Tuber Necrotic Ring Disease associated with infection of susceptible varieties with PVYNTN type isolates.
Powdery scab is a fungal blemish disease. Symptoms can be confused with Common scab. Powdery scab lesions are more uniform in shape and are usually small, round bumps that show up on the skin and stay out of the way. The powder is comprised of spore balls that are released into the soil and can survive up to ten years. These release motile zoospores that infect root hairs.
Powdery scab is also a vector of Potato Mop Top Virus, a cause of spraing.
Notifiable disease
Ring rot is caused by the bacterium Clavibacter michiganensis subsp. sepedonicus.
The disease is favoured by cooler climates. Already established in northern and Eastern Europe, the disease could readily establish under UK conditions. Symptoms are much more likely to be seen in tubers and are somewhat similar to those of brown rot.
Silver scurf is a blemish disease caused by the fungus Helminthosporium solani.
Infection can originate from seed tubers, the soil or from spores remaining in store. Symptoms are normally present at harvest but the disease develops in store.
Affected skin is weakened, prone to scuffing and can wrinkle due to moisture loss.
Skin spot is a blemish disease caused by the fungus Polyscytalum pustulans. Symptoms develop after approximately two months of storage, when the infected tissue begins to show spots on some varieties.
The blemish reduces market value, and even processing crops might require extra peeling to remove well developed symptoms.
Verticillium Wilt: Potatoes
FAQ
How do you treat Verticillium wilt in potatoes?
There’s no direct cure for Verticillium wilt in potatoes, but several management strategies can help control the disease and minimize its impact.
What are the first signs of Verticillium wilt?
Some of the most common signs of verticillium wilt are sudden wilting and yellowing of leaves, leaf scorch, browning (FIGURE 2), and death of leaves, branches that don’t leaf out in the spring, few or no leaves, and the death of part or all of a tree.
What kills Verticillium wilt?
Depending on where you live, you may be able to control verticillium wilt through professional soil fumigation or other means. In warm climates, plastic-covered soil may reach temperatures high enough to suppress the fungi at fault.
Can plants recover from Verticillium wilt?
Partially wilting plants are only partially infected. Partially wilted plants may recover at night till the fungus spreads through more of the plant.
What is verticillium wilt of potatoes?
Compare to good rotation on right. Verticillium wilt of potatoes is a fungal disease caused by either of two species of Verticillium. The disease is found in Maine and in all potato-producing areas of the United States. Verticillium wilt can cause yield losses by a reduction in tuber size.
What is verticillium wilt?
Verticillium wilt is a fungal disease of the vascular tissue of potato and most commercial cultivars are susceptible. The disease usually shows up as splotchy areas in a field and can cause plants to grow shorter, die early, and produce less. Plants may lose turgor and wilt, especially on hot sunny days.
What are the symptoms of Verticillium wilt in potato tubers?
Potato tubers with Verticillium wilt symptoms. Tuber Symptoms: When a cross section of an infected tuber is cut from the stem end, the vascular ring may have brown or black discoloration. The discoloration may extend throughout the tuber but usually is present only part way through the tuber.
Can verticillium wilt cause tuber rot?
Verticillium spp. do not cause tuber rot. However, some potato varieties may turn pink around the eyes or show pinkish brown blotches on other parts of the tuber when infected with Verticillium spp. Pinkeye is frequently associated with Verticillium wilt, but is not a Verticillium wilt symptom.
Do potato viruses cause foliar necrosis?
Depending on virus strain and potato variety, symptoms vary from mild mosaic to severe foliar necrosis to plant death. The most obvious tuber symptom associated with potato viruses is Potato Tuber Necrotic Ring Disease associated with infection of susceptible varieties with PVYNTN type isolates.
How do I get rid of Verticillium wilt?
Use high quality seed from fields without a history of Verticillium wilt problems. Avoid repeated planting of fields to potatoes. Repeated planting of potatoes will increase the incidence of the disease. A crop rotation management plan is the best long-term solution to combating Verticillium wilt.