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Mildew is caused by a variety of different fungi on almost every crop However, the disease can be identified in every crop by white, powdery spots a few millimeters across the leaf, generally starting with the lower leaves. At first, they're easy to wipe off. When the fungus expands, it can cover the entire surface of the leaf, eventually causing the leaf tissue to become yellow and die. There can also be growth arrest, leaves can curl and in the worst case parts of the plant die. Mildew can also grow on the underside of leaves in cases of heavy infestations. The death of the plants is a huge loss and therefore also a loss of production in the greenhouses.

Besides powdery mildew, there is also downy mildew. The difference between powdery mildew and downy mildew is the location of the infestation. With powdery mildew the mold grows on the upper side of the leaves; with downy mildew the mold grows on the underside of the leaves (the discoloration can be visible on the upper side, but the fungus growth occurs on the underside). 

​​​​Downy mildew in cucumber plant​​​​

​​​​Powdery mildew in cucumber plant​​​​

There are several ways to prevent mildew:

• Use resistant crops (if possible). 
• Ensure that the crop never stays wet for too long and that it can dry quickly.
• Increasing the strength of the plant cell, makes it more difficult for the fungi to penetrate. 
• Avoid nitrogen as much as possible, because this promotes the growth of mildew.
• Remove fallen leaves and infected plant parts to prevent the fungus from spreading. 
• It is important to avoid excessive air movement in the greenhouse, since ventilation windows that are wide open can create air into the greenhouse. This is one of the main reasons for the appearance of powdery mildew.

The best way to prevent powdery mildew is to increase crop resilience. 

Powdery mildew control is done by chemical pesticides or by biological pesticides. You can also use a Sulphur Burners to control for powdery mildew. Powdery mildew is combated with sulfur in horticulture, especially since fungicides are decreasing. Sulfur mainly has a preventive effect against mildew. Sulfur disrupts the energy balance in the fungus, causing the fungus to die. Because sulfur has a contact effect, it is important that the sulfur is distributed as well as possible over the crop. You can use a sulfur evaporator for this. You can also choose to use sulfur preventively to prevent damage. In this way, mildew effects are combated in the crop.

Our specialists will be happy to advise you on the various options for controlling mildew. 

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