The Importance of Choosing the Best Fungicide for Powdery Mildew Treatment

Powdery Mildew is a common fungus that attacks a wide variety of plants; it is easily recognizable and virtually no plants are immune to it.

Signs and Symptoms

Powdery MildewPowdery Mildew appears as light gray or white powdery splotches on infected plants. While initially there are few visible spores, the fungus can quickly spread and coat leaves, stems, buds and fruit.

In fruit and vegetable-producing plants, Powdery Mildew will weaken the taste and quality of the produce. It can also stunt plant growth and distort the shape of buds, blooms and fruit. If left untreated, it can cause leaves to turn yellow and drop prematurely. It will eventually kill the infected plants.

Some plants are more susceptible to Powdery Mildew than others. Lilacs, crab apples, roses, grapes, squash and cucumber are particularly frequent targets of the fungal disease. However, it seems to be everywhere.

Powdery Mildew fungi overwinter in plant debris and start producing spores in the spring. The spores are then spread by wind, insects and splashing water. Eventually, they land on plants and under the right circumstances grow and spread.

Conditions that encourage the growth and spread of powdery mildew include humidity, dampness, poor air circulation and crowded planting.

Powdery Mildew Treatment and Management

Powdery Mildew infection is often possible to prevent. It is essential to choose healthy plants, especially resistant cultivars if possible. If disease-resistant varieties of desired crops aren’t available, it’s recommended susceptible plants not be grown in shady areas.

Maintaining good air circulation by first spacing plants properly and then thinning and pruning regularly will also help stave off the conditions Powdery Mildew thrive under.

Should plants be stricken with the disease, there are several steps involved in Powdery Mildew treatment. First, remove and destroy all infected plant parts. After doing so, sanitize garden tools to prevent them from carrying the spores elsewhere.

In addition, while treating Powdery Mildew, do not water from above or fertilize infected plants. The fungus thrives in damp conditions and flourishes on young, succulent plants. Consequently, these actions provide an ideal environment for disease.

Powdery Mildew Fungicide

Application of an environmentally friendly Powdery Mildew fungicide such as OxiDate is also effective in disease prevention and control. It can be applied as a soil drench, pre-planting dip or surface disinfectant.

While there are many fungicides available, OxiDate is especially popular due to it’s rapid effectiveness in treating Powdery Mildew. Because the spores can spread so quickly, a product that works quickly is important.

Powdery mildew treatment – is it working?

We had an inquiry from a customer applying our OxiDate RTS on powdery mildew at a rate of 1:50 and and was not sure if it was killing it. His questions were: should the mildew change color or change visually in any other way? How would he know if it is working or not?

Once powdery mildew sets in, it’s difficult to have an effective control. Hence, preventative applications are recommended early in the season rather than late season applications.

Results Identification

Powdery MildewSymptoms of powdery mildew are white powdery mass of spores on the upper side of leaves. In chemical trials, the effect of a chemical treatment is normally measured by calculating the number of active spore colonies (white spore masses on leaves) on the leaves before and after treatment. The difference in number of active colonies are not observed right after first application and are normally measured at the end of the treatment cycle which involve 6-7 applications.

A grower should able to find differences in white spore mass after a few applications. With chemical control, white spore mass will get discolored over time and the number of active colonies should be reduced. This requires sampling of 10-15 leaves from different plants and counting the colonies before and after treatment.


The recommended curative treatment for Powdery Mildew is 3 consecutive daily applications of OxiDate RTS, at a 1:25 rate (This rate should be ok but ensure by spraying on few leaves for 3 consecutive days and observe for any phytotoxicity over a 48 hr period time after the 3rd application). Subsequent sprays should be at 1:50 rate once every 5-7 days. We also recommend adding a spreader-sticker to the OxiDate solution to help it adhere to the leaves. Nufilm P works well (it actually has some fungicidal properties as well) and should be added @ 0.125%. OxiDate can also be tank-mixed with other natural spreader-stickers like molasses or orange oil.

Applications to treat Powdery Mildew with our agricultural concentrate OxiDate should follow the recommended label rates and instructions.