Powdery leaf mildew

emorems0(PA - 6a)February 16, 2014

Is there anything I can do to prevent it? For the last two years my zucchini plants have suffered through it. I spray with baking soda water and remove the affected leaves. I stake it and tie it up as it grows so it isn't laying on the ground. I lost two pumpkin plants to it the first year (they were just spreading out on the ground and it took a while to figure out what it was that was killing them). My zucchini did okay last year in spite of the powdery mildew, but they could produce so much better and it's such a hassle to keep on top of it.

I'm planting a different variety of zucchini this year, but I'm trading seeds with my sister, so I don't know what specific variety it is or whether it is resistant to powdery leaf mildew.

Is there anything I can do proactively to avoid it this year? I can't really move my zucchini to a different part of the garden without putting some other squash in its place - we rent and I have very limited garden space.

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Yes. Actually, that's the key --- to start treating for it before you SEE symptoms. So, whatever your choice of fungicide( baking soda, potassium bicarbonate, milk, neem oil, etc.), you want to start applying it after you transplant to garden from day 1.

Air circulation is also important and try to plant in the most sunny part of the garden.

Rotation isn't really an important thing for PM, since it needs live tissue to survive. Zucchini usually trucks on through PM, just remove any affected leaves to the vine. It's usually OTHER cucurbits that struggle with it for me.


    Bookmark   February 16, 2014 at 3:12PM
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emorems0(PA - 6a)

My cucumbers get planted right next to the zucchini, so I should treat them too, right? They didn't really seem very affected last year. Maybe because they were more affected by some sort of yellow wilting that I didn't notice much powdery mildew.

Can you tell me more about treatments? I've used baking soda/water because that's what I read can help it and I had it on hand... but it's harsh on the leaves so I tried to only use it where it was already slightly affected by the mildew (really bad leaves were just removed, the baking soda was only on the ones I was trying to save).

I'm trying to keep organic or, more importantly, non-toxic since my little girls like to help in the garden too. Is there a better alternative to baking soda that isn't so harsh to the leaves, but is also non-toxic?

    Bookmark   February 16, 2014 at 4:03PM
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All of the above that I mentioned are organic. I've tried the baking soda and milk before and didn't have too much luck but that was before I knew that proactive treatments were necessary for keeping PM at bay.

Neem works good, but in the summer when it's over 80F or the sum of the temps AND humidity is >140, then you shouldn't use pesticides et al. If you do use, wait until at dusk.

Potassium bicarbonate works well also. And for the money, is economical. I still lost my cantaloupes to PM last year but that was because summer came early here and I didn't practice what I preach by treating from day 1. It won't happen again! You can buy it online but wine and brewer's shops have it also. The brew shops wanted too much but I found a wine shop that sells it for $6/lb. So, shop around. Use at a rate of 4 tsp/gallon of water.

Yep. treat any cucurbit(cukes, squashes, melons) since they tend to be the most susceptible. I did see some on my maters last year, but not bad enough to inhibit production. Peas can also have a problem with PM, but it usually doesn't affect it until they're about done for the season anyway.

As far as the milk treatment, I've heard some rave about it. I also have heard some wide ranging ratios. From 10:1 to 4:1, from fat free to whole. Dunno.

Regarding toxicity, the harshness you mention may have been too much baking soda mixed with water. Try it about the same ratio as the potassium bicarbonate. It may have also been the whole temp thing I mentioned. With any treatment, do at dusk, and if it's going to be a scorcher and/or very bright(sun) the next day, rinse off in the morning. Good idea for any pesticide et al in the dead of summer..

Good luck.


This post was edited by woohooman on Sun, Feb 16, 14 at 21:13

    Bookmark   February 16, 2014 at 8:44PM
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