powdery mildew

[Michelle Silva]

Anyone ever have an issue with white powdery mildew on their plants?? I am noticing it on some of the lettuce, mostly the red variety. I'm planning to spray with milk/water (1:4 ratio) as I read that is supposed to help, but I want to learn what causes it.

[TCLynx]

I once tried an experiment with milk against powdery mildew on pumpkin plants.  I don't think it worked and some one told me that powdery mildew tends to attack plants that are lacking potassium.

 

Milk or lime water are used against downy mildew since changing the pH on the surface of the leaf will help against that.

 

Maxicrop spray might be a better choice if the powdery mildew is actually caused by a lack of potassium.  I would dilute as directed on the bottle.

[Michelle Silva]

Thanks TC. I was hoping to first try something I have on hand. Has anyone added banana peels just to the fish tanks? I don't have gravel beds incorporated into system yet, but may be doing that soon..is that where they are normally added?

TCLynx said:

I once tried an experiment with milk against powdery mildew on pumpkin plants.  I don't think it worked and some one told me that powdery mildew tends to attack plants that are lacking potassium.

 

Milk or lime water are used against downy mildew since changing the pH on the surface of the leaf will help against that.

 

Maxicrop spray might be a better choice if the powdery mildew is actually caused by a lack of potassium.  I would dilute as directed on the bottle.

[Sylvia Bernstein]

Hey Michelle.  I've heard of adding banana peels to a media bed and letting the worms break them down, but never to a DWC system.

I'm using Neem to treat powdery mildew on a chard plant right now.  Seems to be doing a good job.  Not sure about the potassium theory as this is the only plant on a 300 gallon, 4 bed system that has powdery mildew.

[Michelle Silva]

Hi Sylvia, Thanks,yeah, that's the only way I've heard about it too, was just wondering if anyone tried it in fish tanks. I would probably only leave it in for few days, so not sure if it would even be worth it, (4000 +gal) may not even do anything,lol... not sure about that idea.

I've decided to add some gravel beds at the intake into the raft systems so I can have the worms incorporated i/o a separate vermacomposter..should be happening this week.

Sylvia Bernstein said:

Hey Michelle.  I've heard of adding banana peels to a media bed and letting the worms break them down, but never to a DWC system.

I'm using Neem to treat powdery mildew on a chard plant right now.  Seems to be doing a good job.  Not sure about the potassium theory as this is the only plant on a 300 gallon, 4 bed system that has powdery mildew.

[Molly Stanek]

 

From what I've gathered, high humidity and reduced air circulation can contribute to the growth of powdery mildew.  There does seem to be a connection between potassium and plant health in general - maybe the PM is kept in check by a plant with a healthy defense system.

 

For control, you might want to check out this article:

http://attra.ncat.org/attra-pub/bakingsoda.html

 

Keeping in mind the potassium point mentioned above, potassium bicarbonate would seem like a good choice.  We have had good luck with a product containing it at Sweet Water this past summer when our cucumber plants all started coming down with white spots.  Two spray treatments pretty much cleared them up!

[Michelle Silva]

Thank you!

Molly Stanek said:

 

From what I've gathered, high humidity and reduced air circulation can contribute to the growth of powdery mildew.  There does seem to be a connection between potassium and plant health in general - maybe the PM is kept in check by a plant with a healthy defense system.

 

For control, you might want to check out this article:

http://attra.ncat.org/attra-pub/bakingsoda.html

 

Keeping in mind the potassium point mentioned above, potassium bicarbonate would seem like a good choice.  We have had good luck with a product containing it at Sweet Water this past summer when our cucumber plants all started coming down with white spots.  Two spray treatments pretty much cleared them up!

[Chris Smith]

I recently has an outbreak of powdery mildew on some of my lettuce. I needed to spraying Dipel for caterpillars so I added come kelp extract to the mix because of the high potassium. One day after applying the mildew disappeared from all areas that had contact with the spray. I could see where I did not get good coverage with the spray because the mildew was still there. One more application cured the problem completely.

[Kobus Jooste]

I must say, I have also always associated powdery mildew with humidity issues.  In my closed system, I could never keep it off my pumpkins or tomatoes, while everything else was fine.  Before I opened the system up, I tried an organic recipy I found on a gardening site - soak a small amount (two tablespoons per half liter I think) of corn starch in water overnightm then drain of the water (without the starch) and use this as a foliar spray.  Something related to the effect of weat germ was supposed to control the mildew, but it could only hold the mildew off for a day or two at best.  Since I opened the system up, I can grow pumpkin and tomato and cucumber without mildew.

[Chris Smith]

The plants in my covered system were the only ones affected and it is likely due to more humidity under the cover. I designed the cover so it was off the ground and open ends so it would minimize the heat/humidity buildup, but it still traps some. I would rather deal with some minor mildew issues than have crop damage or loss due to heavy rain.

 

I am running an experiment where I am spraying kelp extract every week on one trough and compare it to the others to see if there is a significant difference.

[Sylvia Bernstein]

Chris, I've had good luck with neem oil spray and a fan to increase air movement.

[Raychel A Watkins]

Hey Chris

Where did you get your kelp extract and in what form is it.  Another thing where did you get the uv resistant plastic for your roof.  I have the same problem with the rain.

[Kobus Jooste]

My system also still have the roof up for rain capture, and two of the four sides - I took two sides of the plastic off (the gables have always been shade netting) and the mildew went away.  I had pumpkin and tomato in the very same bed as the pic taken below, and they were constantly full of mildew.  Sides came off, and look now!