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pinksand
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Powdery Mildew Solution

I know this question has been asked numerous times but I'm mostly seeing responses about stressed plants that aren't getting enough water succumbing.

I have 3 zucchini plants that survived our bunnies and groundhogs. One is significantly smaller because it had been entirely nipped to the ground multiple times but the leaves are powdery mildew free. The other two are huge, lush, have plenty more room to grow (not overcrowded) and covered in baby zucchinis so seem to be getting pollinated well. The bed is mulched with grass clippings that seem to keep the soil moist and I water the ground around the base of the plants, avoiding the leaves best I can, each morning. The biggest one, with highest production of zucchini, and the most air circulation is having the worst problem with the mildew. I've lost a lot of the lowermost leaves and it seems to be spreading up the plant. The other large one has the beginning signs on the lower leaves, while the tiny one with only a couple blooms and no signs of actual fruit is unaffected.

Besides removal of infected leaves, what more can I do to help preserve the health of the plants? I know I've seen hydrogen peroxide mentioned... Do I put it in a spray bottle and spray it straight on the affected leaves? Is there a best time of day to do this?

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rainbowgardener
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Yes, you can use hydrogen peroxide straight from the bottle (it comes as a 3% solution). Or you can use baking soda solution: 1 teaspoon baking soda to 1 quart of water, plus a few drops of liquid dish soap. Or diluted milk: dilute the milk any where from 1:10 to 50:50 with water. Let it sit at room temperature for a few hours to culture, then spray on. Only use one of these at a time, but since it will have to be repeated every week or two, you can alternate them.

Spraying is best done early in the AM.

Ksk
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Rainbow Gardne: What time of day do you recommend to spray in a hot climate? Early AM or PM- Dusk? I want to try this but don't want plant to burn up the plant.

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rainbowgardener
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rainbowgardener wrote:Yes, you can use hydrogen peroxide straight from the bottle (it comes as a 3% solution). Or you can use baking soda solution: 1 teaspoon baking soda to 1 quart of water, plus a few drops of liquid dish soap. Or diluted milk: dilute the milk any where from 1:10 to 50:50 with water. Let it sit at room temperature for a few hours to culture, then spray on. Only use one of these at a time, but since it will have to be repeated every week or two, you can alternate them.

Spraying is best done early in the AM.

jeff84
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an aact spray would also be good.

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pinksand
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Thanks everyone! Looks like I'll have to pick one and start spraying this weekend.

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Gary350
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Grocery store vinegar kills mold on contact. Spray plants with 5% vinegar wait about 3 minutes then rinse it off.

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pinksand
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Unfortunately all of my zucchini plants succumbed to vine borers :( My family was watering the plants while I was away on vacation and told me they were looking really wilted. When I got home all of the basal leaves that had the powdery mildew were crispy and wilted and all the new healthy leaves were nibbled by either bunnies or groundhogs. I went to remove the damaged leaves and saw signs of the borers. When I cut one of the stems at the base I found them squirming away in there.... soooooo nasty! I ended up just ripping out all the plants because it was clear they were all infested.

Does anyone have a solution and/or prevention for these guys in the future? I wonder if they borers were impacting the health of the plants and that's why they got the mildew?

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rainbowgardener
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RE: Does anyone have a solution and/or prevention for these guys in the future? I wonder if they borers were impacting the health of the plants and that's why they got the mildew?

The borers would certainly weaken the plant and make it more susceptible to disease. But zucchini is very susceptible to powdery mildew anyway so who knows? :?:

My prevention for the vine borers is not to grow zucchini or other summer squash. I just gave up. It makes me crazy that people say zucchini is so easy to grow and their only problem is how to get rid of them all. (But I think more of those people are in the western half of the country where they don't have the vine borers and low humidity reduces the vulnerability to mildew). So summer squash gets the borers, it gets the mildew, it gets squash bugs which often carry wilt diseases themselves... Just too vulnerable. So I only grow winter squash which the borers don't attack.

But if you insist on zucchini, here's some things to try:
  • Grow your zukes under row cover from the beginning, tightly fastened to the ground. That means you will have to hand pollinate.
    OR try to make the base of the stem where the borers get in impermeable. Keep it coated with Neem oil and/or bury it in the ground and keep burying it as more stem grows and/or keep it coated with kaolin clay and/or keep it coated with sticky Tanglefoot.
Best Wishes!!

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In my humid climate, most of the squashes and pumpkins get powdery mildew. I can delay it with fungicides but I cannot stop it. Usually, I just try to get it to live long enough to fruit. I also select for varieties that are more powdery and downy mildew tolerant. It got Tigress and Parthenon zucchini and they seem to be holding up to the mildew fairly well. I still have to spray them in humid conditions but so far, I only had to take out one leaf. Fruit flies are another story. I have to start covering the fruit, they are all being stung. I prefer sulfur for a preventive fungicide. It has be applied weekly in humid weather and reapplied within a day after it rains. I am experimenting with cinnamon. It helps with soil fungi on orchids, but I am thinking to try it on the squash as well. It should not hurt and it is not temperature sensitive.

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I think so, far, the best strategy has been to choose the earliest maturing possible -- like 55 days -- start them early by pre-germinating and pre-sprouting, then plant early in a mounded or raised bed in the part of the garden that warms up the earliest. Some sacrificial plants should be planted in another part of the garden where they will grow slower and weaker to attract the SVB's. They will likely get infested first, so don't count on them to produce, but if they do, great.

Last year, I harvested something like 2 fruits each from the sacrificial 3 plants before they went down, and the primary 3 plants went down a week or so later, just when I was starting to think I might be harvesting too many yellow squash.

It was just as well because right about then, the cucumbers shifted into full production....

I'm trying late-sowing which is supposed to miss the laying window of the SVB moths, but I'm not counting on them.

There are a few non-C.pepo squash that are said to be good to eat "like" summer squash --immature. I've tried tromboncino, and it IS tasty, but one problem I've ran into is that they are late maturing and take forever to tart blooming. So I'm looking around some more. I've read that butternut squash is good, too, and there ARE several early varieties.

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pinksand
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Ugh, I'm glad to at least know that I'm not alone in this lol but not feeling terribly hopeful about the situation. I'll try neem oil on the stem next year and try to grow more overall. I essentially did grow some sacrificial plants in a shadier garden where their growth was slower, just because I ended up with too many plants for the prime spots. However, those plants were first to get devoured by either the groundhog and/or bunnies... still sacrificial I guess, just to another pest in my garden.

I probably got about 10 beautiful zukes before they declined. My cukes on the other hand are still thriving and producing like absolute mad! I eat them more often so I'd honestly be more upset if it was the other way around. Still disappointing though :(

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rainbowgardener
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You did well to get ten zukes. I usually get a big beautiful plant that produces one or two zucchinis and then melts away to nothing.

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pinksand
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rainbowgardener wrote:You did well to get ten zukes. I usually get a big beautiful plant that produces one or two zucchinis and then melts away to nothing.
I'll count it as a win then!

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rainbowgardener
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I'm thinking about planting some summer squash NOW. I still have about three months until frost ( :) !). The point of the experiment is that maybe by the time they are producing the borers will have finished their life cycle and be gone. However, it is strictly an experiment, because I think here in the South, the borers have two generations in one season. :twisted:

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pinksand
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Definitely sounds like it's worth a shot! You never know, maybe you'll time it just right :)

I'm with you in hearing constantly from people how easy summer squash are! My neighbors have had good luck, although last I checked in with them I was as well so maybe their plants have had issues as well. I have other friends that can't even begin to keep up with their squash plants growing out of control. Meanwhile mine whither away and die :(



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