Zucchini and Powdery Mildew

Friday, 22 August 2008 01:07

Zucchini and Powdery Mildew

Written by Jason

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Powdery mildew is a fungal disease which affects many types of plants. Cucurbits like zucchini, squash, pumpkins, melons and gourds are all succeptable to powdery mildew. It usually appears on leaves as small round white powdery spots which quickly spread and cover the entire leaf. In our garden here at the yardstead we've lost many zucchini, squash and pumpkin plants to powdery mildew. This year powdery mildew killed all of our zucchini and most of our paty pan sqash and yellow squash.
It is usually easy to identify powdery mildew by its appearance on the top of the leaves. It usually looks like white powder on the leaves. Infected leaves usually turn yellow and wilt after just a few days. Powdery mildew usually appears in our garden on one or two plants then quickly spreads to all the other zucchini and squash plants. The infected plants usually don't die completely and frequently send out new leaves and flowers. We have been able to recover from powdery mildew in the garden a few times, when we caught it early and sprayed all the plants with neem oil.
On a few other occasions I applied the funigicide ...........

....too late, after to many plants had spots and lost most of the plants. This year we were planning on spraying our plants with a homemade remedy for powdery mildew (see recipe below), but procrastinated and let them go. We did get several weeks of good fruiting and put several gallons of squash and zucchini in the freezer. We would probably have had a few more good weeks of fruitng if the plants had stayed healthy.
In my experience the best way to deal with powdery mildew is to apply a fungicide as soon as the first signs appear. Once the powdery white spots are spread throught your garden, its probably to late to get good results from a fungicide. Although leaves with spots usually die, new stalks and leaves can continue to grow from the stem, but rarely get large enough to fruit. Most infected plants in our garden stop fruiting shortly after the white spots are visible, although it may take several more days for the leaves to wilt and turn brown. Neem Oil is a good natural fungicide which we have used in the past. It works well if you apply it as soon as the first white spots appear.

Lately we have been using a home made mixture of 1 part milk to 9 parts water, apllied with a spray bottle to the top and bottom sides of the leaves. It seems to work just as well as the commercial products, as long it's applied as soon as the white spots are discovered.

Read 21521 times Last modified on Friday, 16 September 2011 03:53

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9 comments

Comment Link Monday, 05 September 2011 03:34 posted by vicki
help, I think I have this all over my zucchini and paty pan plants...tomotoes next to it ok but pumpkins starting to get it. How do I treat soil so I dont get next year?
Comment Link Thursday, 16 June 2011 14:52 posted by jason
[quote name="kim"]Cut off and get rid of the effected leaves. Then start spraying your plants with milk mixed with water, make sure to get bottom of leaves. Sounds crazy but it works![/quote]
We found some early stage powdery mildew on a few leaves zucchini plants, so we are doing this right now. Will let you know how it goes. We cut off the wilted leaves and sprayed the rest.
Comment Link Saturday, 16 April 2011 22:15 posted by kim
Cut off and get rid of the effected leaves. Then start spraying your plants with milk mixed with water, make sure to get bottom of leaves. Sounds crazy but it works!
Comment Link Saturday, 25 September 2010 07:28 posted by Richard
i just trim the bad leaves off as close as i can to the bottom of the plants. at first they don't look good after the trim, but new ones grow in no time.
Comment Link Saturday, 07 August 2010 14:33 posted by Amy
I read that corn (and corn meal) attracts a good fungus (a type of Trichoderma fungus) which kills off disease causing fungus. So you can either mix in cornmeal into your soil before planting or do crop rotation and plant corn where you had your squash before. (Work 2 pounds of cornmeal into the soil for every 100 square feet. Water well, good for one season.)
The lot I am growing a garden in has just exploded with this fungus on the squash, pumpkin and cucumber, (which are planted in a grassy area). Yesterday I noticed it spread to some flowers and weeds growing around them and I am hoping! hoping! hoping!! that it doesn't spread to my eggplant, peppers and tomatoes which are right beside them only separated by a piece of wood. arg.
I found the info about fungus and corn here:
http://gardening.about.com/od/naturalorganiccontrol/qt/Cornmeal.htm
Comment Link Thursday, 29 July 2010 18:46 posted by jason
There are many different fungi which cause powdery mildew, so it is not impossible, but I have had severe powdery mildew infections on squash and zucchini plants, right next to tomatoes and peppers, and it has never transferred or spread. The powdery mildew has however, spread in my garden from zucchini to other cucurbits such as pumpkins and gourds.
Comment Link Sunday, 25 July 2010 01:58 posted by Jill
Can this spread to like my tomato and pepper plants and kills those?
Comment Link Saturday, 17 April 2010 11:50 posted by Lyle
Fungal diseases like powdery mildew are all too common here in humid Florida. Neem oil can be effective is there is time for it to work. However, all too often, the infection is wide spread before you have time to notice it.
In those cases, I find a light dusting of horticultural sulfur is the most effective method with the least detrimental side effects,
Even so, I use it sparingly because I wonder if it may harm earthworms. I do not know it if does and would love to hear from someone who knew how sulfur affects earthworms.
PS - I love the site
Comment Link Sunday, 28 June 2009 14:00 posted by Tracie
I have been trying to figure out what was happening to my zucchini and squash plants for the past couple of years. It did not matter what I did they would yellow and die. I believe you hit it right on the nose, thank you. It is still early enough for my plants so I will spray them and hope that the situation improves.