Advice to fight tomato blight
by C.L. Fornari
In the summer of 2009, tomato growers in Boston, New York, Philadelphia and Washington, D.C., were hit with a fungus-like disease called late blight. Stems, leaves and fruit developed dark lesions and entire plants collapsed and died quickly, leaving home gardeners disappointed and commercial growers devastated.
Northeast residents commonly deal with two other tomato diseases: leaf spot and early blight. All three problems can prevent us from having what we most desire in the summertime: a tasty, homegrown tomato.
So whether growing tomatoes in pots on the deck, raised beds or in the ground, the question on everyone's mind is how to avoid - or cope with - tomato-leaf diseases this season.
Whether your tomatoes were infected with early blight, late blight or leaf spot, a few simple practices will help to control pathogens this year. Starting with healthy plants is essential. Don't buy seedlings with speckled foliage because these may already have leaf spot.
If you had late blight in your garden last year, don't use seed from those tomatoes to grow this year's plants. In addition, don't plant potatoes from last season's garden; potatoes are in the same family as tomatoes and can harbor disease.
When planting young tomatoes, remove leaves that touch the ground. Early blight fungus lives in the soil, and can more easily infect young plants if they touch the dirt anywhere but their stems. Therefore, it's also smart to mulch around the plants as soon as you put them in the garden. A layer of hay or other mulch will stop rain from splashing fungal spores from soil to leaf.
Begin spraying your plants with a copper fungicide, a natural product, as soon as they are in the garden, being sure to coat the underside of the leaves. Studies show that frequent applications, done according to directions on the bottle, are more effective than infrequent treatments, probably because more of the plant's surfaces are coated.
Many organic growers also apply a natural bacterium, Bacillus subtilis, in between sprayings with copper. B. subtilis is available to home gardeners as Serenade, and it helps to suppress blights and leaf spot.
Although we can't control frequent rain or high humidity, which foster tomato diseases, we can manage how we water our gardens. Water in the morning so that plants have the day to dry, and use soaker hoses whenever possible so that leaves don't get wet. A deep soak less often is better than a little each day.
Inspect plants frequently and promptly remove any spotted foliage, throwing these leaves in the garbage instead of dropping them in the compost or garden. If your plants are infected despite your efforts, continuing with the spraying helps suppress the pathogens enough so that you might harvest the fruit, which is still edible.
One last strategy gardeners can use: the exceedingly wet summer of 2009 helped late blight to flourish, so perhaps a prayer for predominately sunny skies will help!
C.L. Fornari is a writer, gardening expert, professional speaker and radio host who is dedicated to getting you into the garden. The Osterville, Mass., resident is a member of the Perennial Plant Association, American Plant Propagators Society, National Speakers Association and Garden Writers of America.