How to recognize and treat brown rot

the essentials in brief

• The disease occurs not only in potatoes, but also in tomatoes and other nightshades.
• It is caused by the harmful fungus Phytophthora infestans and occurs mainly after damp weather.
• The dreaded tuber rot does not necessarily occur together with late blight, as only the above-ground parts of the plant can be affected.
• Choose potato varieties that are as resistant as possible for a crop, whereby early potatoes are generally less susceptible.

Causes and Spread

In warm, humid weather, potatoes are mainly grown in the period between the beginning of July and the end of August - and until late autumn in - from the dreaded late blight and tuber rot (also called potato rot, even if the disease affects not only potatoes) infected. The disease usually only occurs in connection with rain, in dry weather there is usually no danger. The causative agent of this fungal disease is the harmful fungus Phytophthora infestans, which is usually transmitted by wind, unclean garden tools, infected seeds or poor hygiene. It adheres to the moist leaves and can penetrate these surfaces - because they are swollen and soft - more easily into the plant.

Phytophthora infestans often overwinters in those left behind or stored in the field Potatoes, which in turn - used as seed potatoes the following year - are another source of infection represent. The fungal spores form at temperatures of around 16 ° C and in damp weather for more than ten hours. They are then transmitted by the wind, for example to neighboring plants. Incidentally, the fungus can also survive in the ground after its spores have infiltrated there with the rainwater. For this reason, a permanently moist surface can also lead to an outbreak of the disease.

Damage image

The first sign of potato rot is the twisting of the leaves

Potato rot infection is manifested by the following symptoms:

• Yellowing of the leaves at the beginning of the infection
• then formation of gray or brown leaf spots
• Formation of white-gray fungal lawns on the undersides of the leaves
• All potatoes die off within a few days
• Infestation of the tubers does not always occur at the same time as late blight
• Affected tubers have gray, sunken spots
• Browning of the tubers under the skin

The treacherous thing about tuber rot is that infected potatoes look healthy for a long time and only start to rot if they are stored for a long time. For this reason, you should not set up earth rents and the like in the vicinity of the cultivation areas, and no tubers should remain in the field after the harvest.

Fight potato rot

If the potato rot has attacked the plants, cut the leaves off immediately and dispose of them. Under no circumstances should you throw the infected parts of the plant onto the compost, as fungal spores can stay there for a very long time. In the next year, these may cause a new infection. It is better to dispose of the leaves in the general waste. The tubers themselves can remain in the soil for at least three weeks after the leaves have been removed.

Digression

Plant potatoes in a different place every year

Effectively prevent potato rot

If possible, the potato tops should not be wetted when watering

However, the most important measure to combat potato rot is effective prevention. The following tips will help you contain the disease:

• It is essential that you adhere to the recommended planting distances and do not plant the potatoes too close together.
• Do not plant potatoes and tomatoes (or any other nightshade family) in close proximity to one another.
• Change the area under cultivation annually and keep the crop rotation.
• Never pour from above, always pour directly onto the ground.
• If possible, water in the early morning so that the moisture can dry off quickly afterwards.
• Watering in the evening, on the other hand, promotes fungal infestation.
• Fertilize Do it moderately and in particular avoid over-fertilization with nitrogen.
• Support the defense system of the plants with self-made Herbal manure (e.g. B. Field horsetail or garlic tea) and Rock flour.(€ 12.33 at Amazon *)

Incidentally, the pre-germination of the tubers that you already have in the Position in shallow bowls or egg cartons in a light and frost-free place in early spring can. Under the influence of light, short, green germs sprout from the bulbs' eyes after just a few weeks. This pre-germination gives the plants a head start in terms of growth, so that they mature earlier and the infestation with the fungal disease can be prevented at an early stage.

Digression

These potato varieties are resistant to potato rot

frequently asked Questions

Can you still eat tubers infected with potato rot?

Potatoes infected with potato rot should not be eaten

Since the fungus that causes the disease, Phytophthora infestans, is carcinogenic in its metabolism Toxins produced is from using even slightly infested potato tubers not advised. Cutting out brown areas is also of no use in this case, as invisible threads of fungus still pull through the potatoes. Therefore, remove and dispose of infected tubers and do not eat them. These should not be fed to animals either.

Is the potato rot and the late blight and brown rot that occurs in tomatoes the same disease?

In fact, late blight, brown rot and potato rot that occur in tomatoes are caused by the same fungal pathogen Phytophthora infestans. This means that it is the same disease, which is why you should not grow nightshade plants in close proximity to one another or one after the other in the same bed.

Tip Piling up the potatoes also protects a certain amount of weeds from rotting. It is best to do this step in early summer.