Late Blight Gardener Alert

Late Blight Information for Every Gardener in Maine

An effort of the Maine Late Blight Task Force, a cooperative effort of the University of Maine, the Maine Department of Agriculture, Food and Rural resources, and the Maine Potato Board.

Potato and Tomato Late Blight:

  • Is a community disease, as an infected garden can spread spores and affect commercial potato fields miles away.
  • Can cause severe losses in commercial potato production.
  • Has forced commercial potato growers out of farming. This closes a business and stresses rural families and the local economy.

Before planting, home gardeners can:

  • Use healthy tomato transplants and certified seed potatoes, NOT potatoes from a grocery store.
  • Discard potato seed that has sunken blemishes on the surface with rusty, granular discoloration in the flesh underneath.

After planting, home gardeners can:

  • Allow sufficient space between plants to allow the tops of the plants to remain dry.
  • Protect the growing potato and tomato plants with products containing mancozeb, maneb, or chlorothalonil. These are available at garden centers and should be applied at seven-day intervals or as directed on the label. Local potato growers can also provide advice on spray timing.
  • Check the plants regularly for the disease. If symptoms appear, pull the diseased plant and place it in a plastic bag. Discard the bag without opening it. DO NOT place the diseased plant into a compost pile or leave it in the garden. Both tomato fruit and potato tubers are quickly broken down when late blight attacks them. Noninfected potato tubers or tomato fruits, even if the plant is diseased, are usable.
  • Check the harvested tomato fruit and potato tubers regularly as the disease can progress quickly. Discard infected fruit, plants or tubers in a sealed plastic bag.

For further information, contact:

  • University of Maine Cooperative Extension: 1.800.287.1462
  • Maine Potato Board: 1.800.553.5516