Powdery mildew on grapes

[Happy Chooks]

Last year I lost most of my grapes to what I think is powdery mildew. Is there an organic way to treat this? I prefer not to spray with chemicals.

 

[Mum]

Not sure, but, is powdery mildrew due to damp?

 

[Happy Chooks]

Hmmm, after reading up on it, I'm not sure that's what it is. The grapes grow fine, leaves appear fine, but there is a white substance that comes on the grape bunches when they are growing. We are a dry summer climate here, so I'm not sure now what it is.

 

[Happy Chooks]

It looks like this, which says it is powdery mildew.

http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=569

Maybe I'll try to improve circulation this year by pruning.

 

[Tivona]

Ah yes. Powdery mildew, I know it well. Unfortunately. It grows well on many plants here including squashes, peas, beans, roses and many others. High humidity in the spring can get it going but once it is established hot dry summers will not kill it. Best trick is to kill it before it gets going. Spray then pinch off leaves if you want. Don't use tools or gloves without washing them before and after using near powdery mildew. Yeah its a pain but stopping it early is really the easiest. Once it sets in it is a nightmare to control for the rest of the season. I like the viegar spray

A vinegar spray works fairly well. Use 2 to 4 tablespoons of vinegar, and in 1 gallon of water and spray the plant completely including underside of leaves. I also like adding a about 2 teaspoons of molasses to help it stick sometimes but be careful if you have ants in the area.

Or you can also use a baking soda spray. 1 1/2 tablespoons baking soda, 1 tablespoon vegetable oil, 1 tablespoon liquid dish soap (or Safer Insecticidal Soap...its safe for organics) in 1 gallon of water. The oil, and soap help the soda to stick to the leaves long enough for it to do its work on the powdery mildew.

Just a note, don't mix the vinegar and the soda sprays. They work because of PH level of the spray and what sort of PH the powdery mildew can tolerate. The baking soda spray has a high PH and the vinegar has a low PH. Either can kill the mildew but together they cancel each other out. Also be sure to respray promptly after a rain. And be sure to get all of the plant with the spray, leaves, top and bottom as well as stems and buds. Try not to spray open flowers unless you absolutely must to control a patch of the powdery mildew. Best to use it once a week while you see any problem.

 

[Happy Chooks]

Thanks for the information!!!

 

[Harry75]

My hubby Pruned the grapes to about 2' after they had fruit last yr (their 1st yr) soooooo i guess it will be a long time(yrs) b4 i ever get grapes again, am i right ? Hope we still live here by then i had "white " stuff on my grapes too and then realized it was bird poop, yuck, since i eat them out of the garden all the time ( well, i used to that is)

 

[kmatt87]

Ah yes. Powdery mildew, I know it well. Unfortunately. It grows well on many plants here including squashes, peas, beans, roses and many others. High humidity in the spring can get it going but once it is established hot dry summers will not kill it. Best trick is to kill it before it gets going. Spray then pinch off leaves if you want. Don't use tools or gloves without washing them before and after using near powdery mildew. Yeah its a pain but stopping it early is really the easiest. Once it sets in it is a nightmare to control for the rest of the season. I like the viegar spray

A vinegar spray works fairly well. Use 2 to 4 tablespoons of vinegar, and in 1 gallon of water and spray the plant completely including underside of leaves. I also like adding a about 2 teaspoons of molasses to help it stick sometimes but be careful if you have ants in the area.

Or you can also use a baking soda spray. 1 1/2 tablespoons baking soda, 1 tablespoon vegetable oil, 1 tablespoon liquid dish soap (or Safer Insecticidal Soap...its safe for organics) in 1 gallon of water. The oil, and soap help the soda to stick to the leaves long enough for it to do its work on the powdery mildew.

Just a note, don't mix the vinegar and the soda sprays. They work because of PH level of the spray and what sort of PH the powdery mildew can tolerate. The baking soda spray has a high PH and the vinegar has a low PH. Either can kill the mildew but together they cancel each other out. Also be sure to respray promptly after a rain. And be sure to get all of the plant with the spray, leaves, top and bottom as well as stems and buds. Try not to spray open flowers unless you absolutely must to control a patch of the powdery mildew. Best to use it once a week while you see any problem.

thanks for the tips! i didn't run into this stuff till moving out to CO, and last yr it was BAD. I think every veggies/flower i planted ended up with this junk last yr.

 

[AquaEyes]

Ah yes. Powdery mildew, I know it well. Unfortunately. It grows well on many plants here including squashes, peas, beans, roses and many others. High humidity in the spring can get it going but once it is established hot dry summers will not kill it. Best trick is to kill it before it gets going. Spray then pinch off leaves if you want. Don't use tools or gloves without washing them before and after using near powdery mildew. Yeah its a pain but stopping it early is really the easiest. Once it sets in it is a nightmare to control for the rest of the season. I like the viegar spray

A vinegar spray works fairly well. Use 2 to 4 tablespoons of vinegar, and in 1 gallon of water and spray the plant completely including underside of leaves. I also like adding a about 2 teaspoons of molasses to help it stick sometimes but be careful if you have ants in the area.

Or you can also use a baking soda spray. 1 1/2 tablespoons baking soda, 1 tablespoon vegetable oil, 1 tablespoon liquid dish soap (or Safer Insecticidal Soap...its safe for organics) in 1 gallon of water. The oil, and soap help the soda to stick to the leaves long enough for it to do its work on the powdery mildew.

Just a note, don't mix the vinegar and the soda sprays. They work because of PH level of the spray and what sort of PH the powdery mildew can tolerate. The baking soda spray has a high PH and the vinegar has a low PH. Either can kill the mildew but together they cancel each other out. Also be sure to respray promptly after a rain. And be sure to get all of the plant with the spray, leaves, top and bottom as well as stems and buds. Try not to spray open flowers unless you absolutely must to control a patch of the powdery mildew. Best to use it once a week while you see any problem.

I was about to mention the baking soda, oil and soap solution, but you beat me to it. I've never grown grapes, but the recipe you cited is the one developed by Cornell University and has been shown to be very effective. I used it on any roses that started getting mildew or black spot -- it works just as well for them. It was mentioned in most of my books on roses, but I figured it'd work on any plant.

 

[locke2121]

Would you believe milk works too? Well...for some it does, others it doesn't lol. Mixing about a 20% milk to 80% water and then spraying has given people some really great results for alot of people. Its worth a try!!!