Organic and Chemical Solutions to Get Rid of Potato Scab: Symptoms, Causes, and Treatment

Potato scab is an undetected disease that most gardeners only find out when it’s time to harvest their crops. Once the scab has been removed from these potatoes, they can still be edible; nevertheless, they are in no way suitable for selling. Continue reading to learn more about potato scab disease and how you can protect your crop from it next year.

Organic and Chemical Solutions to Get Rid of Potato Scab
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Below we learn organic and chemical solutions to get rid of potato scabs, what causes potato scab, what are the symptoms of common potato scab, organic and chemical control of potato scab, and scab-resistant potatoes.

Organic and chemical solutions to get rid of potato scab

What is potato scab?

Infected potato seed tubers are a common host for the bacterium Streptomyces scabies, which can quickly spread throughout your garden. Carefully examine any potatoes you plan on bringing into the house, and stick to reputable sellers if you want to ensure quality. The wind, or even rain, can carry it in. It can enter the environment through the fresh manure you use to revitalize your spring garden since it can survive the journey through the digestive systems of animals.

When you’ve spent all season planting, hilling, watering, and weeding, the last thing you want to do at harvest is dug up a pile of scabby potatoes. The bacterium Streptomyces scabies, which causes potato scab, lives in the soil and waits for a favorable environment to reappear. It’s not appetizing, but luckily it’s simple to avoid. Fortunately, the only thing about a bad scab is how it looks. Despite their unsightliness, the potatoes are still edible.

However, you may need to peel them more thoroughly to get to the clean inside. Deeper penetration of the scab occurs in more severe outbreaks. There are several different forms of scab. Lesions are consistently spherical and may eventually join together to form a solid mass. They can be pitted into the potato, giving it a dark, corky appearance, or they can be elevated, giving the spud a rough texture. There is only one scab, and the many appearances you see are due to the different environments in which you find yourself.

How to identify potato scabs?

If a potato scab arises in your garden, knowing the signs can help you identify it. Lesions on tubers are the most noticeable sign of the disease. These lesions can be elevated, pitted, or superficial and can be brown or black. Lesions of shades of tan to brown can also appear on subterranean stems and stolons. However, distinguishing potato scab-infected crops from powdery scab-infected ones might be challenging. Samples should be saved and sent to a local agricultural extension office for testing if you want to know which disease has infected your plants.

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What causes potato scab?

The seasonal occurrence and geographical distribution of scab seem to be largely influenced by soil pH and soil moisture, although other aspects are not well known. The common scab can be devastating when potatoes are cultivated on neutral or alkaline soils (pH 7.0 and above). However, certain strains of the bacterium can cause damage to tubers at pH 5.0 or lower.

It is widely agreed that the disease can be managed well if the pH of potato soils is maintained between 5.0 and 5.2. Increasing alkalinity within pH 5.2–8.0 makes the condition more severe. Particularly at the time of greatest vulnerability to scab, the disease’s occurrence can be dramatically amplified by warm and dry soil conditions.

Organic treatment for potato scab

Seed potatoes should be purchased from reliable sources, and resistant cultivars should be sought if your garden area has a history of scab. The Norland, Viking, Gold Rush, and Russet Burbank are the most well-known and hardy varieties. It’s well knowledge that Red Pontiac and Yukon Gold are especially vulnerable. Add some peat moss to create slightly acidic soil before planting potatoes to protect them against the disease known as potato scab.

Peat is an excellent medium for growing tubers since it is airy and drains quickly. Throwing in a few spruce needles may be a nice touch as well. Avoid growing potatoes in the same spot for more than one growing season. You should put them in the same spots where beans and peas were grown last year since that’s where the nitrogen-rich legumes will have accumulated. Tomatoes, peppers, eggplants, and potatoes are all members of the Solanum family and share pests and diseases.

Perhaps a little sulfur dust will help keep this disease at bay. Wearing protective gloves, place the cut potato in a freezer bag with a pinch of sulfur and toss it as you would with a shake-and-bake recipe. Be careful not to damage any young shoots. Many gardeners highly recommend molasses. In a large mixing bowl, combine 1 cup of blackstrap with 5 gallons of warm water.

Put some of this on the soil beneath the potatoes when you plant them, and then do it again a few times while growing. The molasses, the thinking goes, will promote the growth of helpful bacteria that eventually outnumber the scab. Finally, as your potato plant begins to blossom, it is essential that you water it often (which is when the spuds start forming). Dry tubers are more susceptible to infection, so you should water them every few days after the tubers have started developing.

Chemical treatment for potato scab

Lime, fresh animal manure, and wood ash should not be used excessively. Don’t add more lime than is required if the soil pH is already at 5.2. Dolomitic lime should be used after potatoes in the rotation for optimal results. Sulfur applications that bring the pH of high-pH soils down to the optimal range of 5.0 to 5.2 can help decrease scab levels.

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Potato Farm
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Fertilizers that produce acid, such as ammonium sulfate, should be used. You should use several methods simultaneously to stop the spread of common scab. Compared to relying on a single kind of regulation, this is more efficient. For instance, when a registered fungicide is used with regulated irrigation, the outcomes are superior to either treatment alone. The seasonal occurrence and geographical distribution of scab seem to be largely influenced by soil pH and soil moisture, although other aspects are not well known.

The common scab can be devastating when potatoes are cultivated on neutral or alkaline soils (pH 7.0 and above). Although certain strains of the bacterium can cause damage to tubers at pH 5.0 or lower, it is widely agreed that the disease can be managed well if the pH of potato soils is maintained between 5.0 and 5.2.

Increasing alkalinity within pH 5.2–8.0 makes the condition more severe. Particularly during the time of greatest vulnerability to scab, the disease can spread rapidly when soils are warm and dry. Potato gardeners still face challenges because of the pervasive disease of common scab. This disease spreads via seeds and soil.

Although it can be controlled to some extent by cultural and chemical measures, there is currently no way to achieve long-term, reliable eradication. Researchers are still digging into the root causes of common scab and trying to determine the most effective therapy methods. Persistent efforts can reduce common scab severity in improved management.

Measures to take to prevent potato scab beforehand

During tuber initiation, soil moisture levels below 65% to 70%, or even lower, are ideal for developing potato scab. Potato scab can be avoided if the soil is kept between 80 and 85 percent wet from the time tubers are planted until the potatoes reach a length of an inch and a half. Planting green manure crops such as buckwheat, canola, millet, oat, and rye after potatoes will help reduce the incidence of potato scab.

According to scientific studies, animal manure can raise and lower the probability of potato scab. Higher rates of potato scab have been linked to high soil pH, which researchers think may be caused by animal waste. There are potato types that are resistant to scab. Growing scab-resistant potatoes may reduce the likelihood of dealing with potato scab.

The Atlantic, Dark Red Norland, Kennebec, Norchip, and Superior potato types are well-known for their resistance to common diseases. Potato scab is more prevalent in areas with alkaline soil and is more severe when it does infect a crop. Gardeners should strive to maintain the pH of their soil at or below 5.5 to reduce the likelihood of infection with potato scab and its severity. Acidifying your soil can be accomplished by adding sulfur or acidic fertilizers.

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Potato Field
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Potatoes are more susceptible to potato scab when the soil calcium-to-phosphorus ratio is high. The likelihood of potato scab infection in your crops can be reduced by increasing the amount of phosphorus in the soil or decreasing the amount of calcium in the soil. As you are planting your seed potatoes, inspect them for symptoms of potato scab; don’t use any parts with the disease. There is no assurance that seed potatoes will be free of potato scab, even if treated.

Keeping the soil around your potatoes clean and clear of invasive weeds is essential since it can serve as a food source for potato scab. Particularly troublesome are pigweed and other fleshy-rooted weed plants, and their presence near potato gardens should be minimized to the greatest extent possible.

How do you prevent potato scab organically?

In the garden, plant only certified seed potatoes that have not been exposed to scab. Do not try to grow seeds from contaminated tubers. Choose potato types with some protection against scabs, such as Norland, Russet Burbank, and Superior. Never plant potatoes in the same garden bed more than once every three years. Replace potatoes in your crop rotation with scab-resistant crops, including maize, peas, and beans.

When the soil pH drops below 5.2, scab issues also go away. Garden soils should be acidified (pH below 7) whenever possible. Maintaining a pH of about 6.5 is a happy medium for producing vegetables like potatoes and many others in home gardens. Do not use fertilizers that can raise soil pH, such as calcium, potassium nitrate, or new manure. The next step is to give your potatoes plenty of water, especially while new tubers are developing.

What can you put in soil to prevent potato scabs?

To prevent the occurrence of potato scabs, amend the soil with peat moss before planting potatoes. Because of its porosity and rapid drainage, peat is an excellent substrate for cultivating tubers. Some spruce needles can also be an excellent addition. If possible, avoid planting potatoes in the same area for consecutive years. Plant them in the same locations as last year’s beans and peas since this is where the most nitrogen-rich legumes will be accumulated.

As fellow members of the Solanum family, tomatoes, peppers, eggplants, and potatoes all share the same pests and diseases. Perhaps a little dusting with sulfur dust can help keep sickness at bay. Toss the diced potato with a sprinkle of sulfur and a little olive oil in a freezer bag and shake it as you would with a shake-and-bake recipe, but be sure to use protective hands. Take care not to sever any tender stems.

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Potato Plantation
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How do you get rid of scabs in soil?

If possible, watering the soil again between four and six weeks after planting while the tubers are being set can assist the soil in retaining an acceptable amount of moisture. It has been claimed that bringing the level of soil moisture up to 80–85 percent at the commencement of tuber growth and continuing until the tubers reach a size of 1–1.5 inches can lower the occurrence of common scab.

Does manure cause scab on potatoes?

Scab infections are more likely to be successful in soils with a fine texture and a high percentage of organic matter. Because streptomyces is often engaged in decomposing organic materials in the soil, their presence is suggested to boost the growth of streptomyces. It’s possible that spreading manure over potato crops can make scab infections more widespread.

Gravelly or eroded parts of gardens that tend to dry out quickly are typically places of severe scab infection. This is because coarse-textured soils are favorable to scab, perhaps because of their ability to store moisture.

Which potatoes are resistant to scab?

Russet Burbank, Nooksack, Superior, and Dark Red Norland are examples of some of the varieties that have some resistance to scab. There are a few types of fingerling potatoes that are resistant to the disease as well. Some more likely to develop scab lines are Yukon Gold, Norwis, Shepody, Russet Norkotah, Kennebec, Katahdin, and Defender. Other lines that are vulnerable include Russet Norkotah and Shepody.

Compared to other methods, such as soil fumigation, chemical controls are not very successful. The most effective control method is planting a certified seed inspected and found free of scab lesions. It has been recommended that seed that contains a trace amount of scab contamination be treated with mancozeb. Increase the acidity of the soil by adding amendments. Utilize fertilizers that will acidify the soil, and utilize gypsum instead of lime.

How do you acidify soil for potatoes?

A fertilizer spreader applied 1.5 pounds of horticultural sulfur per 100 square feet of plant space lowers pH by one point. For example, if you have garden soil with a pH of 7.0, the pH will decrease after one application to about 6.0. Since sulfur application rates can vary by manufacturer, double-check those specified on the box. A fractional sulfur treatment will do the trick if you just need to bring the pH down by half a point.

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Potato Harvest
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Utilizing a tiller, add the amendment into the soil to approximately 8 inches. A little sprinkle of water can be used to facilitate the amendment’s dissolution and subsequent addition to the garden soil. To give the amendment enough time to affect a change in pH, the soil should be allowed to sit dormant until the next growing season. While the present treatment is in effect, the high concentration of sulfur in the modified soil makes it unsafe for planting.

If the soil pH has to be lowered by 1.0, repeat the soil test and amendment treatment during the next growing season. A sulfur half-treatment should do the trick if you just need to get the pH down by half a point. Leave the soil alone for a year, then take another pH reading in the spring to ensure it’s in the ideal range of 5.2 to 6.0. Repeat the process yearly to lower the pH to where potatoes can be grown. Don’t plant anything in the garden until the pH level is right.

Are scabby potatoes safe to eat?

Even if they are unattractive, scabby potato tubers can still be eaten. Before being used, infected potatoes need to have their skins removed. Keep tubers that have scab in a cool, dark, and dry location to prevent the scabby regions from getting infected with soft rot bacteria, resulting in the tubers’ complete decomposition.


It has also been shown that heavy irrigation during the development of the tuber is protective; however, you will need to maintain the soil wet for up to six weeks to achieve this result. To succeed with this method, you will need extreme caution; the soil should be kept damp but not soaked. Potatoes grown on soils that are too saturated with water are more likely to experience new issues. If potato scab disease is prevalent in your garden despite your best efforts, you may want to consider planting any potatoes resistant to the disease.


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