How To Stop Powdery Mildew

powdery mildew

My winter squash has what Mud Baron once described as “jock itch for plants:” powdery mildew. I’ve tried all kinds of notions and potions in the past, but this year I decided to see what the science says about powdery mildew. Our climate where I live in Los Angeles is, unfortunately, ideal for producing this vexing fungus.

IPM
Let’s begin with some condensed advice from UC Davis’ Integrated Pest Management page:

Preventative measures:

  • grow resistant varieties
  • find a sunnier spot for the vegetable garden
  • back off on nitrogen

Non-chemical approaches

  • sprinkle plants with water mid morning–add soap for more effectiveness
  • remove infected leaves promptly and dispose of them

Fungicides:

  • apply horticultural oil, neem oil or jojoba oil if the temperature is under 90° F. Do not apply any of these oils if you have used sulfur.

DIY Options
For home remedies I turned to advice from Washington State University horticulturalist Linda Chalker-Scott.

How about milk, widely touted as a powdery mildew treatment? According to Chalker-Scott the answer is yes it might work, but you may need to apply milk before powdery mildew appears. And the studies were done with whole milk, so the effectiveness of other kinds of milk have not been tested. Milk has not worked for me in the past, probably because I applied it too late.

How about baking soda? Chalker-Scott is skeptical. Baking soda has never worked for me.

Compost tea? I hate to bring it up as the topic is insanely controversial. I discovered a tempest in a compost tea pot when I tried to write a non-partisan magazine article about it. Let’s just say I ended up leaning towards the skeptical side when I looked at the evidence. Let me know if you think I’m wrong on this, especially if you can leave a link to a peer reviewed study.

Conclusions
What has definitely worked for me in the past is seeking out resistant varieties. I wasn’t smart enough to remember this fact so I’m going to try the soapy water approach and step up to something stronger if I have to. Part of my problem might also be too much nitrogen–my infected squash is in our straw bale garden and I had to apply a lot of blood meal to get it going. More sun would also help but that would involve cutting down a very large tree. I’ll update this post later in the season.

Let’s hear from you . . .
What powdery mildew treatment have you tried and how did it work? Leave a comment and join the conversation!

And I put the question out on the Root Simple twitter feed and got a few divergent opinions:

Christopher Kennedy ‏@ckpfunk Bonide’s Copper Fungicide for organic gardening. I spray every 14 days this time of year instead of every other w/ baking soda.

Alec ‏@Alec I’ve tried horsetail tea, sea-crop, baking soda, compost tea, and neem oil on mildew, but none compare to milk.

Alissa Walker ‏@gelatobaby I just sprayed with a baking soda solution seems to have done the trick so far. And removed all damaged leaves.

Alex Mitchell ‏@alexmitchelleg give the plants some air, water the ground not the leaves. Could spray diluted milk with water on leaves – never worked for me

What is Killing the Bees?

bees and poppies

What’s the cause of colony collapse disorder (CCD)? We may be getting closer with the release of a study from the University of Maryland about fungicides and other chemicals used in agriculture.

This study is more interesting than many others I’ve seen. It looked at how pesticides interfere with honeybee’s resistance to a common parasite Nosema ceranae. Bees exposed to a widely used agricultural fungicide, chlorothonatil, were more likely to succumb to nosema. The most provocative result for me was that bees exposed to fluvalinate, a miticide used by beekeepers on their own bees, were also likely to get nosema.

Perhaps the villain in CCD is the beekepers themselves. Don’t get me wrong, pesticides probably play a role in CCD. But we must also remember that commercial beekeepers:

  • Treat their bees with pesticides to control mites and these chemicals, as the study points out, harm the bee’s immune systems.
  • Move hives thousands of miles every year to provide pollination services.
  • Place their hives in monocropped areas where their bees can forage on only one kind of nectar/pollen such as almonds in California and citrus in Florida.
  • Use foundation (sometimes made of plastic sometimes made of wax that may be contaminated with pesticides) that does not allow the bees to build their own comb.
  • Regulate (through the use of foundation) the amount of drones the queen can make. Drones may be a sacrificial first defense against mites.
  • Use queen excluders to prevent the queen from moving freely through the hive.
  • Kill the queen and re-queen every year, often using artificially inseminated queens.
  • Import hives from other climates.
  • Feed hives high fructose corn syrup.

Nassim Nicholas Taleb’s new book Antifragile: Things That Gain from Disorder warns about what happens when we prop up and interfere with complex systems like beehives or the economy. When we don’t allow failure (such as trying to prevent mites with chemicals) we set ourselves up for bigger disasters down the road. It’s very convenient to be able to point the finger at the pesticides farmers use. But just like Ben Bernanke, the big beekeepers can’t see the foolishness of their own practices. Point this out at most local beekeeping association meetings and you’ll be shown the door.

This cluelessness is why I recommend new beekeepers avoid most state beekeeping organizations. For a practical and wholistic approach to beekeeping see Michael Bush’s website, The Practical Beekeeper and look at the videos at the Backwards Beekeepers.

Are you part of a natural, no-treatment beekeeping group? Or is your local beekeeping club open to alternative methods? If so, leave a comment . . .

Saturday Linkages: Sidewalk Koi, Papercrete, Jaywalking and How to Grow Fresh Air

Wendy Tremayne and Mikey Sklar's papercrete

Wendy Tremayne and Mikey Sklar’s papercrete masterpiece.

Interventions
Sidewalk Koi http://greenroofgrowers.blogspot.com/2013/08/sidewalk-koi.html …

Worker sent to remove graffiti finds image of himself on the same wall hours later http://fw.to/wOjTzDJ

Let’s Build A Traditional City (And Make A Profit) http://www.andrewalexanderprice.com/blog20130330.php …

Building
Tiny Tea House on Wheels http://feedproxy.google.com/~r/lloydkahn/~3/D2Xib4vOfeY/tiny-tea-house-on-wheels.html …

Straatlokaal Dumpster Structures http://tinyhouseblog.com/construction-articles/straatlokaal-dumpster-structures/ …

Building with Papercrete at the Good Life Lab : http://wp.me/p22K2I-1mgi 

Straw Bale Dome Home in France http://www.naturalbuildingblog.com/straw-bale-dome-home-in-france/ …

Do-it-yourself Pole-barn Building http://www.naturalbuildingblog.com/do-it-yourself-pole-barn-building/ …

Fitness
Healthy Design: 3 Core Engaging Chairs http://www.apartmenttherapy.com/three-unusual-ergonomic-task-chairs-191874 …

Gardening
How to Grow Fresh Air http://www.naturalbuildingblog.com/how-to-grow-fresh-air/ …

Secret Garden of Survival – How to Grow a Camouflaged Food Forest http://www.naturalbuildingblog.com/secret-garden-of-survival-how-to-grow-a-camouflaged-food-forest/ …

How Flora Grubb and an Airport DJ Saved My Soul by Allen Bush http://gardenrant.com/2013/07/how-flora-grubb-and-an-airport-dj-saved-my-soul.html?utm_source=feedly …

Troubles
On Rooftops, a Rival for Utilities http://nyti.ms/15luRcD

The Invention of Jaywalking Was a Massive Shaming Campaign http://paleofuture.gizmodo.com/the-invention-of-jaywalking-was-a-massive-shaming-campa-858926923 …

For these links and more, follow Root Simple on Twitter:

LA Cracks Down On Parkway Vegetable Gardens


Our clueless, incompetent and backwards city government here in Los Angeles apparently has nothing better to do than crack down on parkway vegetable gardens two years after hassling Ron Finley. Steve Lopez, a columnist for the Los Angeles Times, wrote a great column about this ridiculous situation, “L.A. still saying parkway vegetable gardens must go.” And above you can hear Lopez joined by Finley and Councilman Bernard Parks (who sounds like the president of an excuse factory) discuss the situation.

Please Tweet, Facebook, email and otherwise spread the word. My hometown government needs some international ridicule.