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How to control Downy Mildew in greenhouses? 

Downy mildew - just like powdery mildew - is the collective name for a group of fungi that affect green plant parts in various crops. The fungus develops under moist conditions and when the temperature is high enough. The fungal fluff of downy mildew is on the underside of the leaf, unlike powdery mildew, which is also on top of the leaf.
Downey mildew, how to control in greenhouses
Leonie van Rooijen
Product specialist Crop Protection | November 29, 2022 | 4 min. reading time

Identifying Downy Mildew

Downy mildew can be recognized by the gray fungal fluff on the underside of the leaf. In addition, the fungus causes yellow spots on the top of the leaf that sometimes turn brown. These stains are not easy to wipe off. The fungus eventually causes the leaf to die and the fruits to be affected or also to die. Not sure if you have powdery mildew or downy mildew? The biggest difference is the location of the infestation. With powdery mildew, the fungus often grows on the upper side of the leaf, while with downy mildew it is often on the underside of the leaf and in the leaf.

Downy Mildew - Symptoms

  • More severely affected leaves die.
  • Growth and development are impaired when the assimilation surface on the leaves is restricted. In edible species, this affects the yield, in ornamental species, the aesthetics is reduced.
  • The infection can spread to buds, flowers and other above-ground organs.
  • In some species, e.g. lettuce, the base of the shoot is affected first (reduced). The result is the overturning and loss of plants.

Development of  Downy Mildew

Conditions favoring downy mildew are generally high humidity (air and substrate), long-lasting moisture on plants and moderate temperatures (for some pathogens approx. 15ºC, for others 20ºC). The disease develops better at a stable temperature, without large fluctuations. The pathogen overwinters mainly in fallen leaves.

Downy Mildew prevention 

Prevention of downy mildew is always better than cure. To prevent downy mildew you can take the following measures:
  • Make sure that crops can dry quickly. Keep the soil free of weeds and make sure that no water remains on the plots;
  • Do not water the crop over the leaves and do not work in the crop when it is wet. Crop dries faster during the day, so watering in the morning will help it dry faster;
  • Make sure that the crops are not planted too close together, so that they get enough air;
  • Dust the plants with a copper sulfide-based product;
  • When plants are in the right place and can absorb sufficient nutrients, they will suffer less from mildew; 
  • Provide extra water during dry periods so that the plants do not weaken.
If you do discover the fungal disease, remove as many affected leaves as possible. If the soil is also affected by downy mildew, you should change the soil before planting mildew-sensitive plants.

Controlling Downy mildew

Controlling Downy Mildew is done with chemical or biological crop protection agents For an overview of all permitted products for your crop, you can use the Spray Advice Guide.

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Can't find your answer? Fill out the contact form and our specialist Leonie van Rooijen will get back to you. On weekdays, even within 24 hours.
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How to control Downy Mildew in greenhouses? 

Downy mildew - just like powdery mildew - is the collective name for a group of fungi that affect green plant parts in various crops. The fungus develops under moist conditions and when the temperature is high enough. The fungal fluff of downy mildew is on the underside of the leaf, unlike powdery mildew, which is also on top of the leaf.
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Leonie van Rooijen, product specialist crop protection
Leonie van Rooijen
Product specialist Crop Protection | November 29, 2022 | 4 min. reading time
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Downey mildew, how to control in greenhouses
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Identifying Downy Mildew

Downy mildew can be recognized by the gray fungal fluff on the underside of the leaf. In addition, the fungus causes yellow spots on the top of the leaf that sometimes turn brown. These stains are not easy to wipe off. The fungus eventually causes the leaf to die and the fruits to be affected or also to die. Not sure if you have powdery mildew or downy mildew? The biggest difference is the location of the infestation. With powdery mildew, the fungus often grows on the upper side of the leaf, while with downy mildew it is often on the underside of the leaf and in the leaf.

Downy Mildew - Symptoms

  • More severely affected leaves die.
  • Growth and development are impaired when the assimilation surface on the leaves is restricted. In edible species, this affects the yield, in ornamental species, the aesthetics is reduced.
  • The infection can spread to buds, flowers and other above-ground organs.
  • In some species, e.g. lettuce, the base of the shoot is affected first (reduced). The result is the overturning and loss of plants.

Development of  Downy Mildew

Conditions favoring downy mildew are generally high humidity (air and substrate), long-lasting moisture on plants and moderate temperatures (for some pathogens approx. 15ºC, for others 20ºC). The disease develops better at a stable temperature, without large fluctuations. The pathogen overwinters mainly in fallen leaves.

Downy Mildew prevention 

Prevention of downy mildew is always better than cure. To prevent downy mildew you can take the following measures:
  • Make sure that crops can dry quickly. Keep the soil free of weeds and make sure that no water remains on the plots;
  • Do not water the crop over the leaves and do not work in the crop when it is wet. Crop dries faster during the day, so watering in the morning will help it dry faster;
  • Make sure that the crops are not planted too close together, so that they get enough air;
  • Dust the plants with a copper sulfide-based product;
  • When plants are in the right place and can absorb sufficient nutrients, they will suffer less from mildew; 
  • Provide extra water during dry periods so that the plants do not weaken.
If you do discover the fungal disease, remove as many affected leaves as possible. If the soil is also affected by downy mildew, you should change the soil before planting mildew-sensitive plants.

Controlling Downy mildew

Controlling Downy Mildew is done with chemical or biological crop protection agents For an overview of all permitted products for your crop, you can use the Spray Advice Guide.

Contact form
Can't find your answer? Fill out the contact form and our specialist Leonie van Rooijen will get back to you. On weekdays, even within 24 hours.
Leonie van Rooijen, product specialist crop protection
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