05 March, 2010

Thyme to Think About Tomato Blight and Prepare for it Again

The planting season is still a little ways away but with 50* temps in the offing there are some chores that can be started in the garden right now. Or at least begin to think about these projects. My garden is still frozen and the compost may not thaw out until May but I am determined to keep late blight out of my garden this year. Late blight, Phythoptera infestans, is the same blight that caused the Irish potato famine. In 2009 a perfect storm gathered on three fronts that brought about economic destruction for tomato growers and home gardeners alike. First front was the infected plants sold  to mass retailers across the eastern Seaboard. The infected plants were then planted in home gardens and the fungus spread like wildfire.  The fungus that causes late blight can travel forty miles.
The second front was the economy itself which brought record numbers of vegetables gardeners into the foray adding more launch sites for the fungus. The terrible economic conditions had people doing whatever they could come up with to save money. One way to save money is to grow your own food in the backyard. Spending a little money on seeds and plants goes a long way in returning dividends. My bet is that for every $100 one spends on seeds and plants yields several hundred dollars in food.
The third front is really two part. First organic gardening is huge. The trend is gardening is towards using fewer pesticides, natural fertilizers and plants from which seeds can saved and planted the following years .Organic gardening goes hand in hand with heirlooms, old fashioned varieties, that are supposedly better tasting and are not genetically modified (also known as GMO). Victory garden fever has returned, seed saving is a new trend that leads to perfect storm scenario. Heirloom tomatoes are more susceptible to late blight than some hybrid varieties.
There was also a tremendous amount of wrong information in the media about late blight last year. First off ,many newspapers and Internet sights,said that some farmers use copper sulphate on their tomato crops. This is true. copper sulphate, an organic fungicide, is used on tomato and other crops. However it is useless on blight. They may as well have said some farmers water their plants when dry. When this "sound bite" hit the gardening world the though was the answer to blight was copper sulphate because "that's what they said in the paper". And when it was learned that copper sulphate is organic that made the news sound even better. The only fungicide that is even close to being effective is chlorothalanol which goes by the trade name Daconil.  However if not caught when the very first leaf shows signs of the disease that control is of little value.
So what do 50* temps and late blight have in common. Think of your car parked in the sun on a 50* day. Inside the temps rises to over 100*. This is a greenhouse effect. A similar technique can be used in your garden rid it of blight fungus from leftover plant debris or tomato seeds that fell to the ground. This technique is called solarization. Solarization "cooks" the top several inches of soil sterilizing it and making it free of troublesome weed seeds and the fungus that causes blight.
To solarize a section of your garden make sure there is ample moisture in the ground. This should not be a problem this year after the recent snowfall. Cover the garden area with clear plastic sheeting. The clear plastic sheeting will act as a greenhouse roof and trap warm air underneath. Seal the edges of the garden by placing timber, logs, stones etc all around the edge of the garden to prevent heat from escaping. After several days of 50* plus weather, actually 60* is ideal, your soil will have heated to temps in excess of 140* killing off many unwanted weed seeds as well as the fungus causing late blight. The benefit of solarization is that is uses no chemicals whatsoever.
I do not think we have seen the last of late blight. Cold weather does not kill off the fungus. A study of potato farmers in Michigan's upper peninsula showed the fungus over wintered well on potato debris that was left in the fields. Many tomato infected plants were sent directly to landfills last year. This leaves a great storehouse of fungus to spread yet again. Other gardeners simply tossed their diseased plants in the woods or left them in brush piles. This too provides a  great breeding ground for the blight fungus. In addition the fungus can also pass on to future generations in the seed itself.
So there you have my forecast. I think it will be at least another two years before the blight is on it's way out. But one can take precautions to lessen the impact of late blight on this years' crop. Re-consider the varieties you grow this year. Radiator Charlie's, Mortgage Lifter and other old heirlooms carry on tradition, nostalgia, as well as taste into today's garden environment. However many old standby's are like a 1956 Chevy, nice to look at, but a lot of work. If you grow heirlooms this year be prepared to keep an extra eye out for yellowing leaves and prepare to act quickly.
The best word on tomato gardening I can give is know your source when buying plants. Locally grown plants are better for the local economy as well as the environment. There is much less energy used in transporting tomato seedlings from one part of the Hudson Valley to another as opposed to shipping them from Georgia. Also if there is a problem with local material the problem stays local.
Perhaps there is a silver lining to last tomato blight's devastation of 2009. Globilization now makes it easy to get exotic products quickly and cheaply. Globalization also makes it very easy to spread illness around the globe in a matter of hours. Think how quickly the SARS virus spread from Hong Kong to Toronto. If you have never gotten ill from a virus that traveled the world you may not think twice. But last year hardly a gardener I know had many tomatoes. All this from a fungus shipped from single greenhouse in Georgia. Blight hit home last year. Had those tomatoes never been shipped from Georgia the outbreak would have been much smaller or may not have occurred at all.
Buy local, eat local grow local. It's better for all of us.

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