Late Blight Is Back In Northeast!

Devastating tomato/potato disease first confirmed in New York.

Published on: Jul 30, 2010

On Wednesday, Cornell University plant pathologists confirmed late blight (Phytophthora infestans) on tomatoes and potatoes in home gardens in Western and Central New York. That's how this devastating disease started last year and spread across the Northeast.

Weather has been very favorable for this fungal disease across much of the Northeast. Late blight proliferates with substantial rainfall, and long dew periods, reports Carol MacNeil, Cornell Extension vegetable specialist. It has a high risk of overwintering in potato tubers in compost piles and garden soil from last year's epidemic.

If commercial growers have suspicious samples, contact Extension vegetable specialists. Only turgid, green leaves and stems and tomato fruit with suspicious spots can be used to identify the blight.

Late blight symptoms, such as this on potatoes can destroy a crop within two weeks.
Late blight symptoms, such as this on potatoes can destroy a crop within two weeks.

Scout fields carefully, especially edges near trees, where potato "volunteers" from last year emerged, etc. twice a week. Make sure no potatoes are poking out of compost or cull piles!

For one forecasting site, go to the New York State IPM Program's Network for Environment and Weather Applications.

Check out late blight images online. Beginning and keeping up a regular schedule of fungicide applications can protect against infection by air-borne blight spores. Labels for some protective fungicides for homeowner use are available at the Bonide website. Make sure that tomatoes and/or potatoes plus the late blight disease are listed on the label.

Organic growers should use only fungicides approved by their certifier, but may find the following helpful Integrated Pest Management. Commercial growers can check www.nysaes.cornell.edu/recommends/.

Current resources about LB have been summarized by the NYS IPM Program. And check out these webinars for organic gardens and farms.