Late blight first appeared in Washington in 1947, near Prosser. It was next reported in the area in 1974, near Hermiston. It struck crops during seven of the next 16 years and every year since 1990. Late blight is kept in check by good management practices based on research and extension work. Johnson also has a research program aimed at development of resistant plants.
Potatoes are Washington's third most valuable crop.
The line will operate through October.