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managing powdery mildew  RSS feed

 
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I've got a growing problem in my yard with powdery mildew, largely due I think to the ever-increasing lupin population (I broadcast some a few years back and they seem to be particularly susceptible "carriers" without really suffering much as far as their numbers go).

My brother suggested reading Mycelium Running by Paul Stamets in the hope that something in there might address it, but I can't yet find mention of powdery mildew. However, the idea of mitigating fungal disease with beneficial fungus (or rhizobacteria, or other natural agents) intrigues me.

Any thoughts on this or suggestions for further places to look? Thank you for any help you can offer. Last year I about had it when it got all over my cucurbits, and I don't want a repeat this year.
 
Posts: 245
Location: Northern New Mexico, Latitude:35 degrees N, Elevation:6000'
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I think people have been using compost tea successfully to manage/eradicate powdery mildew from their garden plants.?  I really don't know for sure, I've never used it for powdery mildew and it's been a while since I've read information on this subject.

Beneficial microorganisims/effective microorganisims, may be worth looking into as well.?
 
pollinator
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Location: Big Island, Hawaii (2300' elevation, 60" avg. annual rainfall, temp range 55-80 degrees F)
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I don't have a solution for you. Powdery mildew is a big problem for me and I've tried a number of things with no great success yet.

1- remove leaves as they show signs of infection. Boost the plant growth with compost teas or lightly dug in composted manure. The idea is to reduce the infective spores by removing leaves before the fungus on them releases fresh spores while at the same time  promoting rapid regrowth of fresh leaves. I've tried this with squashes, kale, and tomatoes. It helped with the winter squashes so that the plant lived long enough to produce fruits. Some of my gourds actually kept growing for a full year using this method.  Failed with summer squashes. Partial failure with kale. Partial failure with tomatoes (depended upon the variety). I concluded that this wasn't working for me.

2- spray milk or diluted milk solution onto the leaves. I've tried all sorts of dilution rates, sprayed the entire plants top & bottom. Unless sprayed daily, it didn't seem to do anything. Sprayed daily it helped keep it in check long enough for the tomatoes and squashes to produce fruits.

3- baking soda sprays. Worked just about as well as milk solutions, but still not a good solution for me. Required daily full plant spraying.

4- diluted urine sprays. Same as milk solutions. I had to spray daily.

So far I haven't found a cure for it once mildew show up. So this year I'm trying a few new strategies.
1- grow varieties that have some resistance to powdery mildew
2- try compost tea sprays as a preventative and treatment
3- harvest kale as young plants (before mildew traditionally shows up) and plan on succession plantings

Controlling powdery mildew looks to be a daily job for me. I'd like to find a solution that is less time consuming.
 
pollinator
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Mold spores are often laying there on the ground, just waiting to be splashed up onto the underside of leaves when water is carelessly sprayed around the garden.  One way to minimize this is to put a clean layer of mildew-spore-free mulch down around the growing plants.  A bale of fresh wheat/oat straw is perfect for this, but I've also used wood chips (both fresh and aged).  If I've got a bale of straw (I scavenge them after Halloween parties and Thanksgiving displays at stores), I put down a fresh layer of straw mulch about every 6 weeks throughout the growing season.  It tends to disappear quickly as decomposition is pretty rapid in my bacterial and fungal dominated soil.

When you water, carefully try to keep splash-back to a minimum.  Just turn down the pressure so its not blasting everywhere.

Over the years, I'm finding less and less powdery mildew on my plants --- I think that the soil itself has gotten healthier or that there is some other agent at work in the healthy soil that makes the mildew less robust.  Perhaps its a different fungi that has pushed out the powdery mildew fungi.  It's not anything specific that I did to counteract the powdery mildew, other than just continually improving my soil through mulch (mostly wood chips), cover cropping, and multi-species planting.  This past summer was the best I've ever had -- not hardly any P.M. at all.
 
pollinator
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​If you are having powdery mildew regularly, observing patterns might be useful. For example, Istanbul is hit by humid hot air in the second half of July every single year. It creates the perfect environment for powdery mildew. I use season extension techniques to grow pumpkins, to let them to have another month to grow. When powdery mildew becomes unmanageable (like second week of august), pumpkins are about to get harvested.
​Balanced soil and well established fungal network makes a huge difference in my opinion. Does the plants look like they are devoured? Yes. Are they totally covered with mildew? Yes. But they continue to produce. Production is not epic maybe, but they do not shiver and die. They fight back and continue to produce.
 
pollinator
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What has worked for me is a lactic acid bacteria culture diluted and sprayed on the leaves. As with the compost tea, the goal is to establish a probiotic culture on the leaves that makes them an unsuitable habitat for the mildew.
The serum can be obtained from things like yogurt, buttermilk, sauerkraut. Spray new leaves when they emerge and remove damaged leaves. The lactic acid seems to stop the formation of spores but some may have formed before the spray was applied.
 
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Location: Zone 5b Ontario
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I have had good luck with spraying horsetail tea, it didn't get rid of the powdery mildew but the plants stayed healthy and producing through a very damp summer.
 
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Location: North of Seattle
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I've had very good results with a baking soda spray as long as I catch it early enough. 1Tbsp baking soda to 4 Cups water and a squirt of dish soap. I usually only have to spray once every week or two to knock it out. The best though has been watering with a drip system or soaker hoses, eliminates the splashing into the plants and they don't get mildewy to begin with. Good luck!
 
pollinator
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Firstly, over the long term, increasing the available silica in your soil will do wonders for fungal resistance. There are spray products you can buy, there are also silica rich rock dusts you can amend with, my thoughts are that the amendments in conjunction with a horsetail tea (anaerobic to feed the soil, aerobic to spray on the leaves) will do the most to get silica into your soil and available to your plants. As for dealing with an outbreak, I would go with a spray of high ph water followed a day or two later with a culture of bacillus subtilis. You can get it from products called Serenade or Companion (the former is cheaper, I personally have seen better results from the latter) and probably others. My preventative go to these days has become a quick aerated tea (aerated as little as 2 hours, and I would guess you would get some of the effect just from a vigorous few minutes of stirring the ingredients together) of worm castings, insect frass, and bokashi. Sprayed up to once a week throughout the growing season I find that the positive colonization of this microbially rich tea seems to stave off the worst of the powdery. Good luck.
 
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Location: Portland OR
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I've had great success with a product called Neem Ninja, it is 70/30 neem/karanja oils, preemulsified in a ready to use concentrate. Just dilute 1oz Neem Ninja to 1 gallon water, shake and spray on the foliage AND drench the roots. You could simply buy neem and karanja oils and mix and emulsify themselves, but the point is to add karanja because it is a synergist of neem and gets really mind blowing results. It's systemic, safe, works on a massive spectrum of phytopathogenic insects, fungi and nematodes. Your powdery mildew won't stand a chance.
 
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