On one of my zucchini plants (sicilian long zucchoni) I found one of the bottom leaves looks like this. I was wondering if this is an example of powdery mildew. If so, what caused it, and is there anything safe that can be done to treat it, prevent other plants from getting it.
It looks like classical Powdery Mildew, which is very common on cucurbits; although it's rather early for its appearance. I usually see it in late summer. You can find many treatments on the Web; I use fixed copper sprays.
Yes agreed with @vitog, this is powdery mildew. I find that lack of watering on Zucchini causes this problem at an earlier stage in it's development. I use Fungus fighter plus for this. Do make sure you do not leave fallen leaves on the ground and if possible remove any infected leaves now. Ensure futue planting is not too dense so they have good air circulation.
I had Powdery Mildew one very wet year. All the spraying did nothing. Lost cukes and similar and I think all the tomatoes. It never returned in subsequent years. Sure was destructive.
Acerholic, I don't think that you would want to use Fungus Fighter Plus on anything edible. It is a systemic fungicide containing some strange sounding chemicals that you would be ingesting if you used it on Zucchini. Fortunately, I don't think that it is available in Canada.
@vitog yes totally agree it is not organic, but can be used on vegetables. I said in my post that it is what 'I used'. It is up to the reader to make their mind up whether organic methods or not. I don't want to offend anybody by suggesting what I did, so if that happened I am 'sorry'.
Sorry, Acerholic, I just looked at some Web sites that stated that Fungus Fighter Plus is systemic, contains 5-chloro-2-methyl-isothiazol-3-one/2-methyl-isothiazol-3-one, and is used for flowers and ornamental plants. Further research shows that it is also used for cucurbits in greenhouses. I'm not an organic gardener, but I think that using systemic chemicals on edibles is not a good idea.
