When faced with blight, choose to fight


The blight-resistant Mountain Magic from Johnny's Selected Seeds. (Johnny's Selected Seeds)
Contributor October 30, 2013

If you were into themed landscapes you could have called it a Halloween garden. In the summer of 2011, my sister Anne’s tomato patch in Burlington, Vt., had almost overnight become a blackened, slimy mess, a victim of the dreaded late blight.

Unlike lesser fungal blights that plague tomatoes, such as fusarium and verticillium, late blight kills swiftly and completely, with the crop a total loss. The spores spread by wind, especially during periods of cool, wet weather. Any member of the nightshade family, the Solanaceae, might be affected, but potatoes and tomatoes suffer the most. It had become a serious threat in the United States in 2009, and in 2012 it struck Anne’s garden again.

Barbara Damrosch is a freelance writer and the author of “The Garden Primer.” View Archive

A less optimistic person would have given tomatoes a rest in 2013, or at least used a preventive fungicide. Anne took a different approach, based on her confidence that the healthier the plant the more likely it is to resist disease. She mounted an all-out campaign based on everything she had heard about good tomato care.

First, she amended the soil well with lots of compost, for fertility, good tilth and general health. What chicken soup is to people, compost is to plants. Then she bought organic tomato plants. (Starting your plants from seed is also a good precaution — the 2009 outbreak is thought to have spread from box store transplants.)

She also chose to forgo her beloved heirloom varieties in favor of modern ones with disease resistance bred in — the tomatoes with all those letters after their names, codes for the diseases they are less likely to get (the code for late blight is LB). When she set them out she mulched them with bright red plastic sheeting, which has been shown to encourage tomato growth by reflecting back the far-red spectrum of light to the plants’ phytochromes. “It looked horrible, but when the plants got bushy, it was hidden,” she says.

She transplanted her plants into large, square cages reinforced with tall bamboo poles. As they grew she removed all the lower branches below any that were setting fruit. She also pinched out every sucker that formed in the angle between the main stem and the leaf stalks. That kept the plants pruned to a single stem, which made for better air circulation and made all the parts of the plant more visible.

Anne watched for early signs of late blight, such as watery-looking spots and fuzzy white mold on the undersides of the leaves. As a precaution, she picked off every brown or spotted leaf she saw. She watered consistently, being very careful not to let soil splash onto the plants, or even onto the plastic mulch.

And she didn’t get late blight. Tomato envy among her friends was acute. “The tomatoes didn’t taste as great as heirlooms would have,” she reported, “but there were lots of them!”

Why? It’s impossible to say whether the measures she took, singly or together, did the trick. But it’s hard to argue with success.

Damrosch’s latest book is “The Four Season Farm Gardener’s Cookbook.”

Tip of the week

Jonquils are a type of daffodil with small clusters of dainty blooms that do well in hot, dry, sunny locations, making them a great choice for south-facing walkways and slopes, as well as for beach properties. Late flowering and fragrant, they are available for planting now from garden centers and mail-order catalogues. Standout varieties include Fruit Cup, Intrigue, Sailboat, Quail and Bell Song.

— Adrian Higgins

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