Wednesday, July 13, 2011

How my garden grows - Powdery mildew on my zucchini plants!

The leaves on my zucchini plants are covered with a powdery mildew and they are dying.   It’s upsetting because the plants were hearty and vivid and now this. 

Almost no type of plant is immune, however some are more susceptible than others . . . like my zucchini plants. 

Although powdery mildew is unattractive, it is rarely fatal. However it does stress the plant and severe or repetitive infections will weaken the plant. If enough of the leaf surface becomes covered with powdery mildew, photosynthesis is impaired. Infected leaves often fall prematurely. This can be a particular problem on edible crops, since insufficient photosynthesis can diminish the flavor of the fruit or vegetable. If buds become infected, they may not open and mature at all.

The spores are in the ground.  They can be transferred to the plant by wind, insects and splashing water.

Unfortunately, the all the recent rain followed by high humidity encourage this mildew.  Once spores have germinated they continue to grow even in very dry weather. Unchecked, this disease can spread rapidly and significantly reduce crops.

You can prevent the spread of the mildew by removing and destroying the infected parts.  This isn’t an option for me since a large part of my plant is infected . . . I don’t think
k the plant would survive that much amputation. 

It is suggested that you don’t fertilized until the problem is corrected because the mildew favors new growth.  And, it also helps to not water from above . . . which I don’t do in any case.

You can use a chemical fungicide.  However, I found an organic solution which is the preferred method in our community garden.   Milk . . . it is believed that the antibiotic qualities of pasteurized milk impede the germination of powdery mildew spores.

Dilute one part organic cows milk with between five to ten parts water. Stronger solutions can encourage other fungi, like sooty mould, to develop. Spray the solution during the cool of the morning to reduce the risk of foliage being burned in intense sunshine before it dries. Wet both sides of leaves and stems until it begins to drip off. Reapply after rain or irrigation, which rinses this non-persistent solution off. It is most effective when applied in the early stages of infection.

 Fortunately, we have some fruit growing and I'm looking forward to many more.


  1. So now I know what can be the solution in my problem. I also have those powdery dust on my zucchini plants and I just hope that those cow milk will work. Thanks for this blog.

  2. I will try the organic milk solution on my zucchini, vegetable spaghetti and Lebanese cucumber plants also. Will stop watering them from the top too. Thanks for the info.