If you live in the northeastern United States, you've probably noticed the lack of field-grown tomatoes at your local market. You may also have heard that this lack is the result of a particularly bad spell of late blight, a strain of the same potato- and tomato-targeting fungus that caused Ireland's famine in the mid-19th century.
Dan Barber (chef & owner at Blue Hill and Blue Hill at Stone Barns) had a great op-ed piece in Sunday's New York Times explaining the origin of this year's particularly nasty case of late blight. Turns out the summer of 2009 has been a sort of perfect storm of nature, economics, culture, agriculture and good intentions, providing perfect conditions for late blight to flourish like crazy.
First of all, late blight loves cool, wet weather. This summer has been remarkably moderate in temperature and generous with water, so it's no surprise that late blight has made itself at home. Next, you have the economy and current food culture, both of which are encouraging people to grow more of their own food. This is a great trend - food you grow at home is indeed far cheaper, and often better than what you can get in the store.
But since so many people buy their tomato plants from large chains like Home Depot, rather than from small, local nurseries, they're increasing the chance late blight has to hop from plant to plant before making the journey to the home garden. Plants raised in smaller batches can be more closely observed for blight before sale, and have less chance of spreading the disease amongst themselves.
I highly recommend you take a look at Barber's piece, which goes on to suggest some improvements to agricultural training and awareness for professional and amateur farmers alike. In no way does he encourage us to walk back from the current trend for home cultivation, but he does remind us that engaging in agriculture means we should learn a bit about the larger ecosystem in which we're now participating.