Fight back against plant diseases

Jennifer Beaver

From late February through May, my garden enjoys a honeymoon period. The blooms are perky, the leaves are green and sturdy, and I convince myself that this is the year that I will have one of those always-beautiful self-sustaining gardens you read about in glossy magazines.
Well, the honeymoon is over. I found powdery mildew on my cosmos. Never mind that cosmos– a billowy, carefree wildflower– is supposed to be just that– carefree. But there it was, a white powdery substance clinging balefully to the stalks.
A fungal disease, powdery mildew plagues a wide variety of plants. Roses, zinnias, squash and cucumbers are particularly susceptible. Though it doesn’t kill, powdery mildew can disfigure by blocking sunlight needed for photosynthesis.
High humidity, overcast days, crowded conditions can bring it on. June Gloom is the perfect host.
The antidote? Simple. Mix one part skim milk to nine parts water. Shake and spray weekly until the mildew is gone. An enzyme in the milk (use 1% or 2%) combats the fungus. Whole milk will not work.
Then there are the suspicious spots on my tomato leaves. This is a Sungold, a usually trouble-free cherry that ranges happily upward bearing loads of delicious orange bite-size fruit. Generally, they grow like weeds.
But I noticed small black spots on the leaves. Though I am not an expert on tomato diseases– all of them look alike at some stage of development– my Googling and other research leads me to believe that this is Early Blight. Left unchecked, Early Blight can destroy the leaves and ruin the tomatoes. It creeps along, attacking the older leaves first.
Evidently, I’m not the only one. A friend who gardens on the other side of Long Beach brought me some spotted tomato leaves for diagnosis. They looked the same as mine, only worse.
So what should we do? I’m trying a product called Serenade Garden Disease Control, a spray-on bacterial control recommended by Pat Welsh, author of Southern California Organic Gardening. Though this is preventative rather than a cure, I’m still hopeful. Serenade is available at H&H Nursery in Lakewood and other retailers. The organic product has garnered many positive reviews and will not harm beneficial insects. Go, bees!
Plant diseases thrive on moisture. Fight back by watering the soil– not the leaves– early in the day so the sun can dry up any wayward drops.

Jennifer E. Beaver, a Wrigley resident, is a master gardener and author of Container Gardening for California and Edible Gardening for California.

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