I have recently heard from a number of farmers concerned about late blight infestation of tomato and potato crops, and wanted to share with you a valuable new tool available from USPest.org.
Simply go to http://uspest.org/risk/tom_pot_map to find a map of the US which tracks infestation risk in thousands of local areas (see example below).
It takes a little time to load, so be patient.
Information is regularly updated. And from this map you can zoom in on your particular area to get a more detailed analysis of the latest plant disease forecasts based on models which consider degree days and rainfall, to estimate spore formation.
USPest.org also has lots of other great information on identification, forecasting, and control of a wide variety of agricultural pests.