I know most of you are not residents of western Washington, but this information might be of interest to gardeners everywhere.
Pest: Late blight (Phytophthora infestans)
Conditions of risk: cool, moist environment
Found: Images typical of late blight infection on tomato have been submitted from two Puget Sound area (King/Snohomish county) farms. Growing conditions were plants in field soil where the area was covered with a plastic hoop structure.
Potential impact: Significant crop losses may occur if not managed properly.
What action should be taken: Scout for evidence of the pathogen on the foliage, stems of tomato or potato, as well as the fruits of tomato. Look for black discoloration to the foliage and a halo of sporulation around the edge of the damage if conditions are moist. Keep the foliage as dry as possible. Maintain good air circulation around plants. A variety of preventative fungicides (both organic and conventional options) is available – click on the links above for tomato and potato.
Information is also available on the PNW Plant Disease Management Handbook website.