Potatoes are actually quite robust plants. However, they are susceptible to various diseases and parasites. Read here what they are and how to fight them.
Many hobby gardeners who have some space in their garden grow potatoes. These also taste much better from your own garden than from the supermarket next door.
But if you grow your own vegetables, you have to expect that various diseases and parasites can spread.
Potatoes are particularly susceptible to pests when the soil is too dry in summer. But fungi in particular also have an easy time on a substrate that is too damp.
Today we will briefly present the most important potato diseases and provide information on how you can recognize and combat them.
The 5 most common potato diseases
1. Late blight
This late blight is the most common in potatoes. It destroys up to 30 percent of the potato harvest in our latitudes. Good ware potatoes are particularly sensitive, the crop failure can even be up to 50 percent. This fungal disease is a very old disease. More than 150 years ago, entire stocks of this fungus were destroyed in many places. The tubers rotted and many people starved to death.
The fungus needs a moist environment to spread. There is already a risk of infection when the leaves are formed, and the spread is particularly rapid in warm, humid weather.
Recognize
You can see brown, slightly sunken spots on the leaves, and there is a white coating on the underside of the leaves. In the summer, when it's warm and humid, the spores of the fungus disperse very quickly.
Fighting
In summer, fighting is almost impossible. If the herb of the potato plant dies, the fungus also dies. But in the meantime it has long settled on other potato plants. So you can only prevent late blight. Even when planting the potatoes, you should pay attention to resistant varieties, which are inferior varietiessignificantly more susceptible to fungal infections.
An optimal fertilization of the potato plants is also extremely important, the plants are much more susceptible to too much nitrogen. If the weather is very humid in late summer, you can hardly avoid using chemical agents.
2. The potato scab
In contrast to tuber blight, potato scab is not caused by fungi but by bacteria. These bacteria called Streptomyces scabies are found in all areas of Germany. However, they mainly affect potatoes grown on a light sandy soil. The pathogens penetrate the growing tubers, and infection occurs particularly during the first 14 days of tuber formation. Especially when the soil is very dry due to high temperatures.
Since the pathogen depends on a lot of oxygen, it has a particularly easy time in loose soil. The bacteria also develop more easily at higher pH values, so at a value of less than 5.5 there is rarely an infestation with potato scab. Basically, the scab is nothing bad, there is hardly any loss of harvest and the taste of the tubers does not suffer either. The only problem with such scabbed areas is the fact that other parasites can penetrate there particularly easily. If you store these potatoes later, they will shrivel faster.
Recognize
You don't recognize potato scab early on, because you can't see anything on the cabbage. Only the tubers are attacked. Brown spots with cracks can be seen there. If the infestation increases, these merge into larger areas that are scabbed over. Sometimes the appearances remain superficial, but the scab can also work its way into the tuber.
Control
You cannot control this disease directly, appropriate pesticides are not available. You should therefore definitely grow resistant varieties. Previous green manuring with rye, vetches or lucerne is also helpful. You should not plant beets after the potatoes, because this crop rotation also promotes an infestation.
The plants should be irrigated while the tubers are developing, if possible you should not work the soil to prevent loosening. Potato scab is not a serious infection in private gardens because it does not make the tubers inedible.
3. Blacklegs
These tooBlackleg can be more common in potato plants. Like tuber wet rot, blackleg is also caused by bacteria. You only have to reckon with harvest losses from a certain degree of infestation. Infection is particularly common on heavy soil, as waterlogging easily occurs. There are also certain potato varieties that are much more likely to be affected, including Satina, Adretta and Nicola.
Recognize
Parts of the plant wither, turn yellowish and eventually die. Above all, the stem is damaged, at the base of which the typical black discoloration can be seen. The plants are easy to pull out of the ground, and there is a pungent smell.
Fight
Fighting blackleg is hardly possible, so prevention is the top priority. This begins with the selection of varieties that are as resistant as possible.
You should hold back on watering in summer. This is only indicated if the drought persists. Wait two to three weeks after the above-ground parts of the plant have withered before harvesting, only then will the skin of the tubers be sufficiently hard. You should absolutely avoid fertilizing with stable manure with potatoes.
» Tip: Annual crop rotation can be a good preventive measure.
4. Early BlightThe early blight is also a fungal infection. The potato plants are attacked primarily in dry, warm weather in summer, and tomatoes are also affected.
Recognize
Especially on the underside of the leaves small brown spots can be seen, which also have concentric rings. The spots are also often outlined in yellow.
The disease can not only manifest itself on the leaves, but also spread to the tubers. The wind and rain ensure that the fungal spores are distributed, they can then survive the winter in the dead plant parts and then cause a renewed infection in the coming year.
Fight
Affected leaves should be removed immediately and the potato plants should be well ventilated. Sometimes there is no avoiding the use of chemical pesticides. The tomato and fungus protection Consento or the copper fungus protection from Gesal are helpful, for example.
5. The potato crab
A fungus is also responsible for potato cancer, namely Synhytrium endobioticum. The infestation occurs onStem base and tubers open.
Recognize
The name of the infection is no coincidence, because growths occur that are reminiscent of cancerous tumors that look like cauliflowers. These cell proliferations can vary in size and can reach the size of a fist. At first they are still light, but as they progress they take on a dark colour, and then a black powder emerges.
» Note: Even if the potatoes are stored later, the infection can continue to progress. The upper parts of the plant can be perfectly he althy while the tubers are already rotting. Potato canker is a notifiable disease, cultivation may only be resumed on the affected area after it has been proven that it is free of infestation.
Fight
The infestation can be very severe, especially in cooler, damp areas. Combating potato cancer is not possible, and chemical agents are not available either. You can only prevent by using resistant seedlings and paying attention to crop rotation. Potatoes should therefore only be grown in the same place every four to five years.