Prepare soil for planting, managing soil-borne pests and disease

Q: Black scurf

A fungus called Rhizoctonia solani causes a disease known as black scurf of potato. It can be found in all potato growing areas in the UK, particularly in cold and wet soils. If you have noticed small, black or brown irregular lumps on your potatoes which look like soil and can be scratched off, it could be black scurf. Black scurf of potato symptoms and damageWhile signs of black scurf are often visible on tuber skins, the most damaging effects of the disease take place underground. The fungus attacks potato seed sprouts and can weaken or kill them before they emerge. Later in the growing season, the fungus attacks stolons and brown lesions develop, which are known as stem cankers. Superficial lesions don’t interfere too much with plant growth, however large, severe lesions can affect the functioning of stolons and stems, preventing them from moving starch from the leaves to the tubers. Stolon cankers can also reduce tuber numbers and size, as well as causing tubers to be misshapen. This has an inevitable impact on marketable yield. Controlling Black scurf of potato An integrated approach is best for protecting your potato crop against black scurf. Applying a fungicide to seed potatoes is the key to successful black scurf treatment. Planting seed potatoes in warm, well drained seed beds can help reduce the risk of infection as can longer rotations.

Q: Silver scurf

What is silver scurf in potatoes?Silver scurf is a seed-borne disease of potato tubers caused by the fungus Helminthosporium solani. Symptoms of silver scurf include tan or grey lesions which start at the stem end of the tuber surface, making it appear ‘shiny’ when wet. Infection can originate in infested soil, infected seed potatoes, or infected tubers in storage. The disease usually spreads when rain or irrigation disperses fungal spores through the soil. Once in storage, high temperatures and humidity encourage the disease to develop.Silver scurf damageSilver scurf infection damages the skin of potato tubers. This affects their quality and appearance, sometimes making them unmarketable. Silver scurf control Early lifting can reduce the risk of silver scurf infection as can getting out in the field and checking tubers for signs of the disease. Treating tubers with a fungicide before planting or at harvest when they are in store can prevent infection. Keeping stores clean and well-ventilated can also help.

Q: Common scab

Common scab in potatoes is caused by Streptomyces scabiei bacteria. The bacteria are soil-borne, thrive in dry soils, and invade through the tuber skin during early development. If bacteria are present, a common scab potato will have an unpleasant looking brown discolouration of the tuber skin. This may appear as raised spots or it can cover the entire tuber surface. Common scab damageThe disease won’t have much of an effect on yield or storability, however quality can be affected due to the scab lesions. Controlling common scab Maintain soil moisture levels and plant scab-free tubers, ideally resistant varieties. Apply a seed treatment like MAXIM 100FS to combat the disease in the field.

Q: Rhizoctonia

What is Rhizoctonia fungus?Rhizoctonia solani is a common seed- and soil-borne fungus. It’s responsible for causing black scurf on tubers and stem and stolon canker on underground stems and stolons. The fungus thrives in cold and wet soils, and it will grow faster than potato plants in these conditions. Rhizoctonia solani symptoms include reddish-brown lesions on stems near ground level. In some cases, the lesions are present on stolons and can pinch off sprouts before the plants emerge, which can result in the loss of the tuber. Another tell-tale sign of the presence of Rhizoctonia in potatoes is black scurf. You’ll see sclerotia (hard black masses) form on the skin which won’t easily wash off. Rhizoctonia damage Rhizoctonia can cause yield losses due to stunted plants. Quality is also affected because the disease causes the tubers to become discoloured and/or misshapen. Controlling Rhizoctonia in potatoes Management of Rhizoctonia requires an integrated approach. To reduce incidence of disease, plant shallow into warm soil, starting with coarse-textured soil. Increasing the amount of soil organic matter can reduce the risk of disease as can treating tubers with a fungicide such as AMISTAR.

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Managing soil-borne pests and diseases

for a healthy potato crop

Soil pests along with seed and soil-borne diseases can be economically damaging for potato growers because of the impact they have on crop health, yield, and quality. Crop protection is a vital part of your integrated pest management plan, and we offer targeted solutions that consistently protect your crops.

Soil pest management for healthy yields

Ensuring potatoes get off to a good start is essential for a healthy yield. Treatment is an ongoing process, with solutions that target specific soil pests at different stages of the potato lifecycle from pre-planting though to the completion of the canopy.

Here we detail the most important soil pests and pathogens affecting potatoes, the damage they cause, and how you can manage them so you can take steps to protect your crop.

Soil pest control

Learn more about soil pest management strategies and their impact on your potato crop.

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Potato Cyst Nematode (PCN)

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What is potato cyst nematode?

PCN, a parasitic worm-like organism, is the most challenging soil-borne pest for potato production. There are two species of PCN, Globodera rostochiensis and Globodera pallida. The latter is the most difficult to control and it has become more widespread due to favourable weather conditions and the cultivation of potato varieties that are more susceptible to infestation.

Potato cyst nematode damage to potato crops

PCN damages crops at various stages of its life cycle. The PCN cyst is the dead body of a female nematode, and it contains around 600 eggs. Each egg produces a juvenile. Juveniles develop and moult within the egg and become second stage juveniles. They then invade the roots of the plant, stunting root growth, and settle in the important vessels which help the plant take up nutrients and water from the soil. This causes considerable yield losses.

Potato cyst nematode control

To control PCN and protect your potato crop, incorporate a granular nematicide such as NEMATHORIN^®10G into your integrated pest management plan. Granular nematicides have been shown to reduce the multiplication of post-cropping populations of both species of PCN as well as reducing yield losses.

The process of applying granular nematicides should follow the guidelines set out in the Nematicide Stewardship Programme (NSP), of which Syngenta is a member. The programme provides industry approved best practise to ensure accurate application whilst reducing risk to the environment. Without this stewardship, legislative bodies will not continue to register nematicides for use.

More information on the correct application can be found here.

Free Living Nematode (FLN)

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What are free living nematodes?

FLNs are parasitic soil borne pests which feed on the roots of potato crops, reducing crop yield quality. They can also transmit viruses. FLNs are most often found in sandy and light open-textured soils, and they reproduce very quickly when soil temperatures are between 15°C and 30°C.

Free-living nematode damage to potato crops

FLNs are particularly damaging to potatoes because they transmit a virus called Tobacco rattle virus (TRV), causing spraing, a tuber disorder. As spraing affects tuber quality, it can make potatoes unsaleable. If spraing is present, you will notice brown flecks, circles or lines through the tuber as well as short stems and discoloured leaves.

Free-living nematode control

To reduce the threat of FLNs to your potato crop, take an integrated approach to soil pest management. As well as using soil testing to monitor FLN populations, use NEMATHORIN to control spraing transmitted by free living nematodes in potatoes.

Wireworm

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What are wireworms?

Wireworms are the larvae of click beetles. They are soil pests which feed on and burrow into plant roots and tubers all-year round for 4-5 years before they pupate. Even relatively low populations can cause significant damage to potato crops.

Wireworm damage in potatoes

If there are wireworms in potatoes, there will be small, round holes on the surface of potato tubers which lead to narrow tunnels. This damage can result in yield loss, seedling death, and a considerably less marketable potato crop.

Wireworm control

To prevent wireworm damage in potatoes, there are several things you can do.

Control weeds as they can be an extra food source for wireworms.
Consider lifting your potato crop early if you expect a problem with wireworms.
Use soil sampling to get an idea of the population size.
Use a proven treatment such as NEMATHORIN, which reduces wireworm tuber damage.

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PROTECTING POTATO CROPS FROM SEED AND SOIL-BORNE PATHOGENS

Black scurf

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A fungus called Rhizoctonia solani causes a disease known as black scurf of potato. It can be found in all potato growing areas in the UK, particularly in cold and wet soils. If you have noticed small, black or brown irregular lumps on your potatoes which look like soil and can be scratched off, it could be black scurf.

Black scurf of potato symptoms and damage

While signs of black scurf are often visible on tuber skins, the most damaging effects of the disease take place underground. The fungus attacks potato seed sprouts and can weaken or kill them before they emerge. Later in the growing season, the fungus attacks stolons and brown lesions develop, which are known as stem cankers. Superficial lesions don’t interfere too much with plant growth, however large, severe lesions can affect the functioning of stolons and stems, preventing them from moving starch from the leaves to the tubers. Stolon cankers can also reduce tuber numbers and size, as well as causing tubers to be misshapen. This has an inevitable impact on marketable yield.

Controlling Black scurf of potato

An integrated approach is best for protecting your potato crop against black scurf. Applying a fungicide to seed potatoes is the key to successful black scurf treatment. Planting seed potatoes in warm, well drained seed beds can help reduce the risk of infection as can longer rotations.

Silver scurf

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What is silver scurf in potatoes?

Silver scurf is a seed-borne disease of potato tubers caused by the fungus Helminthosporium solani. Symptoms of silver scurf include tan or grey lesions which start at the stem end of the tuber surface, making it appear ‘shiny’ when wet. Infection can originate in infested soil, infected seed potatoes, or infected tubers in storage. The disease usually spreads when rain or irrigation disperses fungal spores through the soil. Once in storage, high temperatures and humidity encourage the disease to develop.

Silver scurf damage

Silver scurf infection damages the skin of potato tubers. This affects their quality and appearance, sometimes making them unmarketable.

Silver scurf control

Early lifting can reduce the risk of silver scurf infection as can getting out in the field and checking tubers for signs of the disease. Treating tubers with a fungicide before planting or at harvest when they are in store can prevent infection. Keeping stores clean and well-ventilated can also help.

Black Dot

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Black dot is a soil-borne and tuber-borne disease caused by the fungus Colletotrichum coccodes. The fungus enters potato plants through injured leaves or stems, or via underground stems. Black dot is often mistaken for early blight as it shares similar symptoms, namely wilting and nutrient deficiencies. It is more likely that it is black dot in your potato crop if you see mid-late summer yellowing and wilting of the top leaves in the canopy and tiny sclerotia on stems, tubers, stolons, and roots. At the end of the season, you can identify black dot on your potato crop by checking lower stems and petioles for silvery black lesions.

Black dot in potatoes damage

While black dot is a mild disease which won’t kill potato plants, it does have an impact on plant health by making them vulnerable to other diseases. Black dot can also affect tuber size, weight, and crop yield quality.

Controlling black dot in potatoes

An integrated approach which includes the management of crop pests is the best way to prevent black dot infections. An early-season application of a fungicide, focusing on the plant stems plus planting in well-drained soils can help. You should rely on the principles of good crop management to protect your potatoes; carry out visual checks out in the field, ensure crops have enough nutrients and water, and manage other pests.

Common scab

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Common scab in potatoes is caused by Streptomyces scabiei bacteria. The bacteria are soil-borne, thrive in dry soils, and invade through the tuber skin during early development. If bacteria are present, a common scab potato will have an unpleasant looking brown discolouration of the tuber skin. This may appear as raised spots or it can cover the entire tuber surface.

Common scab damage

The disease won’t have much of an effect on yield or storability, however quality can be affected due to the scab lesions.

Controlling common scab

Maintain soil moisture levels and plant scab-free tubers, ideally resistant varieties. Apply a seed treatment like MAXIM 100FS to combat the disease in the field.

Rhizoctonia

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What is Rhizoctonia fungus?

Rhizoctonia solani is a common seed- and soil-borne fungus. It’s responsible for causing black scurf on tubers and stem and stolon canker on underground stems and stolons. The fungus thrives in cold and wet soils, and it will grow faster than potato plants in these conditions. Rhizoctonia solani symptoms include reddish-brown lesions on stems near ground level. In some cases, the lesions are present on stolons and can pinch off sprouts before the plants emerge, which can result in the loss of the tuber. Another tell-tale sign of the presence of Rhizoctonia in potatoes is black scurf. You’ll see sclerotia (hard black masses) form on the skin which won’t easily wash off.

Rhizoctonia damage

Rhizoctonia can cause yield losses due to stunted plants. Quality is also affected because the disease causes the tubers to become discoloured and/or misshapen.

Controlling Rhizoctonia in potatoes

Management of Rhizoctonia requires an integrated approach. To reduce incidence of disease, plant shallow into warm soil, starting with coarse-textured soil. Increasing the amount of soil organic matter can reduce the risk of disease as can treating tubers with a fungicide such as AMISTAR.