How To Fight Powdery Mildew On Cucumbers

Last updated on October 23rd, 2023 at 08:33 pm

Cucumbers grown on their own are absolutely delicious and healthy. It is not at all difficult to grow cucumbers. Only powdery mildew, which really often takes over the plants both in the greenhouse and in the open field, is a real nuisance.

What causes powdery mildew?

The pathogen is a fungus. Two species of powdery mildew fungus occur on cucumbers, Erysiphe cichoracearum and Spaerotheca fulginea. The layman can not distinguish between them, and in the end it does not matter. In summer dry weather, the disease spreads rapidly. In humid weather, powdery mildew is slowed down. However, there is no need to rejoice too soon. Humid weather favors downy mildew.

Prevention with resistant varieties

How To Fight Powdery Mildew On Cucumbers

There are now numerous varieties of both pickling and salad cucumbers that are highly resistant to downy mildew. So if you choose the right variety, powdery mildew no longer plays a role. So it is quite easy to do something against these troublesome pathogens. With resistant varieties, the disease can still break out, but the disease incidence is much lower. Resistant varieties have firmer or harder plant tissue, which makes it more difficult for pests to penetrate the plant. In resistant varieties, the plant is completely immune to pest infections. Infestation remains limited to a high degree.

Control powdery mildew on cucumbers

Powdery mildew is found on the leaf surfaces, downy mildew on the undersides of the leaves. Usually sprays are used for control, whether biological or chemical. You need to know which pathogen to control and spray on the right side or both.

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Home remedy

  • The most effective home remedy for powdery mildew is milk, skim milk to be exact. This is diluted and sprayed over the infested leaves. The process must be repeated a few times, but then you have peace.
  • Dilute skim milk 1:6 with rainwater.
  • Spray once a week
  • Skim milk diluted 1:3 strengthens the plant when watered with it
  • Watering also once a week
  • Dilute normal milk 1:9

Nettle liquid manure is also a good choice for powdery mildew. Dilute the liquid manure 1:10. Primal rock flour in the liquid manure helps against the stench. Watering can be done before the outbreak of the disease is even thought of, i.e. from the very beginning. This strengthens the plants and makes them more resistant. In addition, the liquid manure acts as a fertilizer.

  • Dilute nettle liquid manure
  • Spray over the plant if it is infested.
  • Otherwise, water normally with the liquid manure

Garlic is also said to help against powdery mildew. To do this, two cloves of garlic cut into small pieces. Over them pour half a liter of boiling water. The mixture must cool, then the garlic is filtered.

  • Pour boiling water over garlic
  • Leave to cool
  • Pour the mixture into a spray bottle and spray.
  • Spray with saline solution is also said to help against powdery mildew. Half a teaspoon of salt is dissolved in a liter of water. Then spray with it.

Another preventive measure is to plant certain plants between the cucumbers, which powdery mildew does not like at all. In this way, the cucumber plants are protected. Basil, chervil and chives should do a good job in this regard.
It is important to eliminate weeds between the cucumber plants. Powdery mildew is often transmitted by weeds.

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Chemicals against cucumber powdery mildew

Conventional means against fungal diseases are usually offered as a ready spray mixture or as a concentrate for dilution. It is important that the agents are compatible with bees. It is favorable if one treatment is sufficient and if the agent helps against several nuisances, not just one.

  • Net sulfur, e.g. Netz-Schwefelit® WG from Neudorff – spray powder against powdery mildew on outdoor cucumbers.
  • Fungisan® Rosen- und Gemüse-Pilzfrei – against many important fungal diseases, including powdery mildew and downy mildew on cucumbers in the greenhouse and outdoors, active ingredient azoxystrobin
  • Compo Ortiva Universal Pilz-frei – long-lasting effect, rather expensive, active ingredient azoxystrobin, effective against powdery and downy mildew
  • Vegetable fungus-free Saprol from Scotts Celaflor – active ingredient azoxystrobin, strengthens the plants at the same time, acts against powdery and downy mildew
  • Bayer Garten Spezial-Pilzfrei Aliette – active ingredient Fosetyl, fast-acting, cures and prevents, for watering and spraying, effective against downy mildew
  • Compo Duaxo Universal fungus-free – active ingredient difenoconazole, against powdery mildew and some other diseases, has a preventive and curative effect.


Powdery mildew on cucumbers can hardly be avoided, unless you use resistant cucumber varieties. Then you are largely protected against this disease. Those who use normal cucumber varieties should use plant strengthening agents. Against powdery mildew works spraying with a mixture of milk and water. I would try Sakhalin perennial knotweed and ELOT-VISgreen. I don’t use chemicals unless there really is no other way and there are fallback options here. Powdery mildew on cucumbers does not have to be. If you want to avoid modified vegetables and do not like to use F1 hybrids, you can rely on milk and natural control. This is also well possible.

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  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts. Jones James

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