Curse You, Powdery Mildew

Why, oh why, do my squash plants have powdery mildew?

And what, oh what, do I do about it? 

This is the first crop in my new, improved spiral garden. So needless to say I was very disappointed when I saw my pumpkin, zucchini, and cucumber vines develop powdery white spots. 

What is powdery mildew? The bane of my existence, that’s what it is. (Sorry for the outburst.) Powdery mildew is a fungal disease that starts as a few spores on the leaves, and quickly spreads.

Spores overwinter on bits of a diseased plant, and then begin asexual production. New spores are carried via wind to other parts of the plant or, gulp, to other plants close by. 

Powdery mildew spores never stop producing more spores. If the infected leaves aren’t destroyed, the situation will only become worse.

Why is it so important to get rid of powdery mildew?

Besides being ugly, the mildew eventually causes leaf drop, and stunted growth, as well as distortion and dropping of blooms, buds, fruit, and overall weakness of the plant. 

The weirdest thing I learned about powdery mildew is that it hates water. It thrives in dry conditions with temp between 60 and 80 degrees. It prefers dry, shady conditions with poor air circulation.

How to guard against powdery mildew?

You could just plant powdery mildew resistant plants or you could plant in full sun away from the shade and make sure there is plenty of air circulation in between plants. Make sure to inspect plants daily and remove leaves at the first sign of mildew.

What to do if you get the dreaded powdery mildew?

After swearing, remove infected leaves and stems and destroy. Make sure to destroy the diseased parts and do not compost them (you want to get rid of those prolific spores) 

Remedies?

I have heard that you can make a baking soda spray and use it weekly at the first signs of infection. Supposedly this protects plants against further damage. Of course plants that are badly infected should be pulled out and destroyed to keep powdery mildew from spreading.

I have also heard that, believe it or not, plain hose water can be an effective treatment in preventing and treating powdery mildew. Just spray the foliage of your plants daily with plain hose water. This method works best if your plants are sprayed in the morning so the foliage has a chance to dry out.

I will get back to you with my progress in the fight against this Evil Fungus.

Comments

[Janelle of Vacaville]

I have ended up with the same issue. My lemon cucumbers and my squash all have powdery mildew to the extent that it's affecting production. I have been removing plant parts, but so much of the plants have been affected I am ready to just pull out the summer garden and get ready for fall. (My corn failed to make silks.) UGH!

What are you doing? Any luck?

Why doesn't composting kill the spores? The city of Vacaville has a compost bin, should I just put all the plant parts in the regular garbage?

[chigiy]

HI Janelle,
Powdery mildew is hard to get rid of once your plant gets it. A friend of mine who has a vineyard says once the average daily temp goes over 70 degrees, he sprays his vineyard every 10 to 14 days with wetable sulfur or stylet oil, both of which are organic.

I am going through the same thing you are. I probably should just rip out all my infected plants but they are still producing and it's hard for me to dispatch them when there is fruit on the vine.

The spores just float around and composting wont kill them. So, yes, they vines should be placed in the trash or else the disease will spread.

good luck.