I have quite a problem with powdery mildew come our "monsoon" season here in Southern AZ. Once the rains come, PM spreads through the squash and melons (watermelon and muskmelon) pretty quickly. I've tried a few things, sulfur spray, Neem, and a 10% milk mixture, but, so far, the mildew doesn't suffer too much. I do get decent yields sometimes--we had a ton of Waltham Butternuts this past summer despite the PM, but it'd be nice to find a solution to the problem, whether it be an effective fungicide or resistant varieties. Any suggestions?
Powdery Mildew
Most of the modern squash hybrids (winter or summer) have Powdery mildew resistance. Also true for melons, Primo or Yuma Grand may be good varieties for you. Don't have problems with PM on watermelons so I only know a couple of PM varieties. Lemon Krush, Red Delicious
Don't have the link where I got it, but:
"Mix 1 heaping teaspoon of baking soda, 1 tablespoon of dormant oil, and 1/2 teaspoon of insecticidal or dish soap in one gallon of water as a PM spray. Plants should be well hydrated prior to spraying; irrigate a couple of days in advance of spraying."
Quote from WillyFromAZ :
I have quite a problem with powdery mildew come our "monsoon" season here in Southern AZ. Once the rains come, PM spreads through the squash and melons (watermelon and muskmelon) pretty quickly. I've tried a few things, sulfur spray, Neem, and a 10% milk mixture, but, so far, the mildew doesn't suffer too much. I do get decent yields sometimes--we had a ton of Waltham Butternuts this past summer despite the PM, but it'd be nice to find a solution to the problem, whether it be an effective fungicide or resistant varieties. Any suggestions?
This is an informative link: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7406.html
Helps to know the life cycle and what to do when!
Dawn dishwashing liquid is said to work, but I don't remember the recipe.
Buster, thanks for the link. I do believe one of my major errors is not catching the mildew quickly enough. I also know that Neem and the milk solution remedy (from OG mag, also from Mike McGrath of "You Bet Your Garden") don't cure the problem once it's established. They may slow it down, but they ain't a 100% remedy. I can also say that bright sun and temps above 90°F don't bother the PM strain(s) that bother me. I will try resistant varieties this year and keep a closer watch. Any other suggestions are still welcome, folks, so don't be shy!
Daconil is effective with powdery mildew and has low toxicity. It's the only non-organicically certified chemical we use in our garden and is a last "gun" though I don't know why because most of the organics we use are at least as toxic. Farmerdill's suggestion of hybrids are worth a try. He always gives good advice. So try some Walthams and his suggested hybrids side by side. Walthams are my favorite. I'd rather spray if needed. It's not needed every year.
I'd not dream of putting home brew insecticides or fungicides that were gleaned off of an internet site. If you have a good yield leave it alone. That is the goal. Try spacing a bit further apart or ground watering early to delay the PM onslaught. I've used milk and Neem. Both help but if you live in a climate that has a season/weeks of continuous rain, you can't spray often enough to prevent the problem. You need to re-spray every time the plants get wet and that's impossible when you have a rainy season. Tried it and failed.
The mechanism behind milk spray effectiveness, according to my understanding, is it requires sun to inhibit and ultimately kill the action of fungal spores. If it's raining constantly that would obviate the result.
Laurel
We have heavy dew every morning and PM is a constant problem. Catching it early is the key. I watch the fruit, they will show signs before there are any spots on the leaves. I have used the milk spray (more a preventative), neem (be careful, it can burn leaves), Organicide (also burns leaves, not very effective) and copper/sulfur mix. I think alternating is good. We are organic, but if I were to buy a fungicide and use it, Daconil would be my spray of choice.
I have been using row covers more and more. The plants growing under those don't get mildew as badly as the ones not covered.
WillyFromAZ - I'm sorry to say this, but when I lived in South Florida, PM was so bad, I gave up growing melons/squash/cucumbers after the first couple of seasons!
What is dormant oil? I use Murphy Oil Soap in the garden. It smells great and works well. Be sure to spray really, really early in the AM or late in the PM so the leaves don't burn.
Stepanietx--Dormant oil, aka horticultural oil, is an oil based spray that is typically sprayed on dormant fruit trees to kill overwintering insects; I'm sure there are other uses. It is used by organic folks--it's even discussed and recommended in Organic Gardening mag books. The stuff I've used is Volck Oil Spray (by Ortho, I'm sure there are others) and is available from most any complete nursery. As used by TX_gardener, above, it is probably (I'm guessing) in the mixture to help with adherence to the plant leaves.
Thanks for the info. I have just never heard it referred to as that. Will keep an eye out for it.
I was reading about Safer's Soap the other day. It is recommended for PM, but haven't tried it.
I haven't tried it yet, but I've read good things about horsetail tea:
Quoting:
. Horsetail Tea (Equisetum arvense)
The common horsetail plant, which is very invasive, is rich in silicon and helps plants to resist fungal diseases via increasing their light absorbing capabilities. Use on peach trees to control peach leaf curl. Use on most plants to combat powdery fungi, and on vegetables and roses to control mildew. You can use this on seedlings and plants in closed environments too! Great in greenhouses! Prevents damping off. Horsetail is one of the ingredients in Golden Harvest Fertilizer.
To make:
In a glass or stainless steel pot, mix 1/8 cup of dried leaves in 1 gallon of unchlorinated water. Bring to a boil, then let simmer for at least 1/2 hr. Cool and strain.
Store extra concentrate in a glass container. Will keep for a month.
Dilute this mix, adding 5-10 parts of unchlorinated water to one part concentrate. Spray plants that show any symptoms of fungal type disease once every 4 days. Spray your seed starting mixtures to prevent damping off.
http://www.ghorganics.com/page15.html
That's just one recipe. I've seen other that call for using horsetail ash, which was interesting.
Just be sure to used the right species. Equisetum arvense is the frilly horsetail, not the straight & smooth one.
TX_gardener, I think that is the Cornell recipe for PM and blackspot on roses. It is a well tested tool to fight those problems. I just printed off the recipe and tacked it to my shed/greenhouse wall so I can remember to just make it and not buy it (it is available comercially). I swear I could just for get my head lately!
Have a difficult time deciding if I'm unfocused or ... oh well can't remember what I was gonna say. I'm probably just trying to do too many things! :)
Ohhhh, I think I'm just gettin' old ='. But maybe its just that I spend too much time here at work. Somehow I think that might be it.....I used to be able to remember all of these little things. Just came naturally to me. Sigh! Yes, yes, that must be it--the 50 hour work weeks! Not old, not old....
NOT OLD!!!
I'm OLD - that's my excuse and I'm sticking to it!
(Actually, too much sugar in one's diet will cause "fuzzy thinking")
OK--so how does one go about getting horsetail....?
It's a native plant and it's range is the whole US, so you might get lucky & find it in a field somewhere. According to the USDA it can be found in either wetlands or non wetlands.
http://plants.usda.gov/java/profile?symbol=eqar
Since it's known to be useful as a natural/ herbal remedy, there are enterprising people packaging & selling it in various forms, either on the web or in natural food stores.
I have it in my field. It's very primitive looking when it first comes up.
Oh, TX_gardener, I hope I didn't upset you. I'm the one who is getting old! I've just had to get trifocals =8~O! I wasn't implying anything about anyone else!
t_e -- no offense! The all caps were for emphasis and I was talking to myself, as in "I am not old" ......... :)
Mary
=+D Cool! That's what I was hoping, but sometimes its hard to tell when no faces are involved.