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.

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