Pest Alert for western Washington – late blight

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)

Hosts at risk: Tomato and potato

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.

2 thoughts on “Pest Alert for western Washington – late blight”

  1. Ooh, late blight. Late blight swept through veg. gardens here in MA a couple of years ago, and ruined whole tomato crops. In a wet summer season, it only takes a few short weeks, almost, to devastate a planting. Fortunately, the blight doesn’t survive our chilly winters (though I wonder about last winter, which was extremely warm), so the problem won’t necessarily recur in a second year. But while the fungus is active (we learned that it likely started here from tomatoes bought at big box stores), it can and will decimate a crop, and using the few good parts of any tomato for relishes, salsas, etc. — is usually the only way to salvage any part of the year’s production.

  2. Well, I guess one benefit of the hot and extremely dry summer we are having is a low probability of late blight. Actually, looks like a good year for tomatoes as long as I remember to water.

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