A couple of summers ago, gardeners in many areas of the East were devastated to find their once healthy tomato plants dying within a matter of days. What started as a few water-soaked spots on the leaves and stems spread rapidly until the entire plant collapsed in a heap. The cause of all this devastation was late blight, a disease caused by the fungus-like pathogen Phytopthera infestans, which strikes potatoes as well. It was late blight that decimated the potato crops in Ireland in the mid-1800's, leading to the famine that caused so much suffering and led to the immigration of so many of the Irish to our shores.
Late blight can be a serious problem just about anywhere in the country if weather conditions are right. That's why the USDA has set up the website www.USAblight.org. Led by a team of 25 university scientists throughout the county, the site offers a wealth of information about late blight, including color photos to help with identification and information specifically for home gardeners.
There is an occurrence map showing where confirmed outbreaks have happened -- in Florida, California, and North Carolina so far this year -- and a place to report new outbreaks. Tips for managing late blight are provided, with links to additional state-specific information for a number of states. There is also a link to the Cornell University Potato/Tomato Late Blight Decision Support System, set up to help commercial growers decide when the application of preventative fungicide applications is warranted.