My neighbor has a medium sized tree right against our common fence that had a bad case of powdery mildew, so he decided to cut it down today. We have plants on the other side of the fence, and a lot of the powder was in the air, and a few of the branches fell on our side of the fence, spreading even more of it.

Should I be worried about effects on other plants? We don't have the same tree, but we have a lot of other trees and veggies, including a Goji plant that gets something similar.

Also, is it dangerous to be around the powder? We both wore masks while he was cutting it. I sprayed the area with water to wash it off the fence and plants - hopefully that was OK. Our weather has been sunny and hot lately, if that matters.

Thanks for any help or suggestions.


Powdery mildew is a collective term for related and common fungal infections on many plants; some are more likely to occur when the weather is dry and very warm. It does reproduce and spread spores in the air at certain times, but may be spread by insects too. Some plants are more susceptible than others, but it's best to treat the mildew as soon as it appears, or before it appears if you know you have certain, vulnerable plants. The milk remedy is as good as many commercial fungicides, but regular spraying is necessary - the mix varies, but is most usually 1 or 2 parts cows milk to 9 or 8 parts water, sprayed till run off on all leaves. Because the spores of various fungi are always in the air, they are something you breathe in every day without being aware of it, and breathing in a few powdery mildew spores should not cause you any serious health problems unless you are particularly allergic to fungal spores. Further information here https://www.rhs.org.uk/advice/profile?pid=253

  • Thanks a lot for the info, especially the milk mixture. I think my wife has used milk, but having a formula is useful, as I may be able to dial it into a hose-end sprayer for a large area. The rhs.org link looks especially useful - straightforward, understandable, without going overboard. – Marty Fried May 12 '19 at 16:34
  • To stress more about Bamboo answer: powdery mildew is species or gender specific. If you see it in one plant, it will indicates that the climate is good for it, but very probably it will not cause infection to other species. So keep it as warning: you are in a zone with powdery mildew danger. The good: powered mildew is one of the few diseases which can be cured (not just blocked). – Giacomo Catenazzi May 13 '19 at 6:32

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