Zucchini is one of the most popular vegetables to grow in the garden. The culture isn’t complicated either, and even a beginner can easily handle it. Only mildew causes problems for the plants and thus also for the gardeners. A distinction is made between real and downy mildew. Both are fungal diseases. You have to recognize them in time and fight them as quickly as possible. In the worst case, the entire plant can die.

Characteristics of powdery mildew

  • White, mealy spots on the surface of leaves, stems, and fruits
  • Initially, the stains are easily wiped off
  • The white spots merge with each other over time and cover more or less the entire leaf, stems and fruit
  • Leaves turn brown and eventually die
  • Fair-weather fungus – usually occurs during long periods of drought and heat
  • Mainly caused by two different types of fungi
  • Can occur individually, but also together on a plant
  • Fungal spores survive on plant debris
  • Transmission through the air
  • Spores can only survive on living plants, so combating them is much easier than with downy mildew
  • Too much nitrogen favors the infestation

Characteristics of downy mildew

  • Whitish to brownish, velvety coating on the underside of the leaf
  • Additional brown or yellowish spots on the upper side of the leaf
  • Coating can also occur on stems, buds and flowers
  • Bad weather fungus – usually occurs in rainy and cool weather
  • Mainly occurring in spring and autumn
  • The spores float on a film of water on the leaves and penetrate the plant through stomata. The mushroom lawn cannot be wiped off.
  • If left untreated, the fungus will spread. The plant parts eventually die off
  • At the end of the year, permanent bodies are formed, which cause new infestations in the spring

Control powdery mildew on zucchini plants

No matter what mildew it is, it is important to check the plants regularly and to intervene as soon as the first symptoms are detected. The affected leaves and plant parts should be cut out immediately. In the case of a severe infestation, it is even advisable to rip out the entire plant and dispose of it so that the fungal spores cannot spread further.

Tip : It is recommended to use a plant strengthener. An infusion of horsetail is ideal for this. It is mainly preventative. The contained silicic acid strengthens the surface, making it more difficult for fungal spores to penetrate.

Ingredients for this :

  • Soak 300 g fresh or 30 g dried plant parts in 10 liters of water for 24 hours
  • Heat everything up and simmer for 15 minutes
  • Let cool down
  • Dilute with water in a ratio of 1:5
  • Spray the plants thoroughly from all sides
  • Repeat several times a few days apart

You can also use fungicides preventively, but you should make sure that they are approved for growing vegetables.

Combat powdery mildew

Fight the disease as early as possible, at the beginning of the disease, with Celaflor® vegetable fungus-free Saprol® = a systemic spray that penetrates the plant and spreads throughout it. But it also acts superficially as a contact poison. This remedy can be used up to 3 days before harvesting the zucchini. The active ingredient azoxystrobin is a synthetically modified substance from the group of strobilurins. Their toxicity is very low for humans and animals. The substances are also rapidly degraded in soil and water. It is important to follow the instructions for use.

  • Baking powder, rapeseed oil and water spray – 3 packs of baking powder to 5 liters of water and 3 to 4 tablespoons of oil. Spray the white spots thoroughly from all sides. Repeat treatment after rain.
  • Mix milk or whey with water in a ratio of 1:5 and spray well
  • Plant garlic, chervil, or chives among the zucchini to help ward off powdery mildew
  • Ladybugs and sawflies love the fungus lawn and will eat it up, so should be encouraged
  • Thin out leaves to ensure good ventilation

Combat downy mildew

Downy mildew is more difficult to control than real mildew. It is therefore advisable to take preventive measures from the start. It helps, for example, never to water the leaves, i.e. not to get them wet. If it cannot be avoided, it is better to water in the morning and not in the evening so that the leaves do not get wet in the cooler night. Experts recommend destroying rather than fighting a plant affected by downy mildew so the spores can’t spread.

  • Strengthen plants to prevent
  • Garlic or onion infusion
  • Large planting distances, ventilation is important. The leaves and plant parts must dry quickly after getting wet
  • Moderate watering and fertilizing
  • Don’t water the leaves
  • Do not fertilize too much nitrogen
  • Better fertilize with potassium
  • If infested, remove as many infested parts of the plant as possible
  • Dispose of all parts in household waste
  • Also remove weeds, they serve as carriers
  • Pesticides help if they are used early enough

Frequently Asked Questions

Is it safe to eat zucchini infected with powdery mildew?
If it’s powdery mildew, then yes. It is not harmful to human health because it does not produce any toxins. What can happen is that inhaling the spores can cause allergic reactions in sensitive people. I would no longer eat zucchini infected with downy mildew, because the fungus has invaded.

Are there any zucchini varieties that are resistant to powdery mildew?
Very resilient and healthy are:

  • Dundoo – dark green, glossy fruits, cylindrical shape, especially early variety, said to be resistant to all diseases
  • Excalibur – slightly fruity taste, good mildew resistance
  • Mastil F1 – green variety, ideal as raw food, very compact and robust, resistant to powdery mildew and viral diseases
  • Mirza F1 – green fruits, grafted variety, very compact, resistant to powdery mildew, yellow spot and mosaic virus
  • Radiant F1 – dark green, glossy fruits, very compact, resistant to powdery mildew and yellow mosaic virus

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