Powdery mildew on cucumbers: how to get rid of it

Both powdery mildew and downy mildew can bring the cucumber harvest to an abrupt end. The fact that they attack the popular plant can never be completely avoided. It is all the more important to effectively destroy the fungal pathogens. With our instructions, you can do this in an environmentally friendly way.

Check cucumber plants regularly

For successful control, it is crucial that you discover powdery mildew as early as possible. Both plants outside in the bed and in the greenhouse are affected. Check your cucumber plants regularly for symptoms of these fungal diseases. Both species can be easily recognized and distinguished from each other, although the distinction is not decisive for control. Below is an overview of the typical symptoms:

Powdery mildew (Erysiphaceae)

• Powdery mildew loves hot and dry summer weather
• is also known as the fair-weather mushroom
• a mealy-white fungus lawn can be seen on the upper side of the leaves
• the spots are small at first, but quickly become larger
• Leaves turn brown and dry up
• the whole plant dies

Downy mildew (Peronosporaceae)

• Downy mildew loves moisture and rain
• as well as cooler temperatures (10-18 °C)
• The undersides of the leaves first show watery, angular spots
• they are increasingly covered with a gray to violet mushroom lawn
• Cucumber leaves turn yellow within a few days
• they die off, starting from the edge of the leaf
• the whole plant dies

Act early, discard late

If a cucumber plant is badly affected, you should not waste time with useless measures. Instead, remove them completely from the bed or greenhouse so that the fungal pathogens do not spread to other cucumber plants or overwinter in the ground. Otherwise, you should start fighting immediately, because the fungal pathogens spread quickly.

Tip: Plants affected by powdery mildew do not belong in the compost. The pathogens would survive in it and return to the beds together with the mature compost. Put all plant parts in the residual waste bin or the municipal organic waste bin.

Remove badly affected leaves

Sometimes not the entire plant is covered with a fungus lawn, but some leaves or tendrils are strong. You should cut away and dispose of these and only then take further control measures. Clean the scissors before and after cutting to avoid spreading to other plants.

Injections with natural agents

Natural pesticides help against both types of mildew and are environmentally friendly. They can therefore be used several times without hesitation, so that the powdery mildew is really completely defeated. In addition, they are readily available and almost free. Spray the cucumbers preferably in the evening, never in the blazing sun. Do not leave out any parts of the plant.

baking powder

The baking powder is the main ingredient, but there are other ingredients as well. Adjust the recipe below to get the amount you need:

• 100 grams of baking powder
• 100 ml rapeseed oil
• 1 tbsp washing-up liquid
• 10 liters of lukewarm water

nettle manure

Nettle manure is routinely produced every year in many home gardens. Diluted 1:10 it can also be used as a spray against powdery mildew. If you don't have ready-made nettle manure at hand, use another method to avoid wasting time.

garlic tea

Cut four cloves of garlic into small pieces and pour 1 liter of boiling water over them. After the brew has completely cooled, it is filtered and is immediately ready for use.

milk

Mix skimmed milk with rainwater in a ratio of 1:6. Sprinkle all the cucumber leaves with it. This solution, which is considered the most effective against powdery mildew, is also suitable for watering the plants.

Sakhalin knotweed infusion

The Sakhalin knotweed, scientifically Reynoutria sachalinensis, is considered a problematic neophyte, so it should not be specifically settled. However, if you have access to a plant, it can be useful against cucumber powdery mildew. For this purpose, 10 g of dried leaves are poured over with 1 l of hot water, filtered after several hours and sprayed onto infested cucumber plants.

saline solution

If the fight has to be quick, you can also use salt, which is available in every household. Dissolve half a teaspoon of it in a liter of water and spray the cucumber plants with it. However, do not repeat this spraying as often as the salt will get into the soil.

Chemicals

Several chemical agents against powdery mildew are waiting on the store shelves. Since their use is questionable, check carefully whether and which one you want to use, especially since the household remedies described above are good for mildew. If it has to be a fungicide, choose the least evil that is effective in small quantities and spares the pollinating insects. If necessary, ask the specialist store what the current supply situation is.

Prevent cucumber powdery mildew

• Observe crop rotation of four years
• Use plant strengtheners
• Plant basil, chervil or chives between cucumbers
• Consistently remove weeds from the bed (carrier)
• Ventilate the greenhouse in the mornings and evenings

Grow resistant cucumber varieties

Growers know the problem with cucumber powdery mildew. They have therefore developed many varieties that are tolerant or resistant to powdery mildew and downy mildew. Here are a few F1 hybrids:

pickled cucumbers:

• capra
• Excelsior
• dragon-fly
• Othello
• restina
• Schubert
• zircon

cucumbers:

• Burpless Tasty Green
• Dominica
• Euphya
• jazzer
• solvent earth
• Styx (hothouse cucumber)
• Sudica

mini cucumbers:

• passandra
• Printro

Learn more about plant diseases