Signup to receive email updates

or follow our RSS feed


Blog Archives

368 Total Posts

follow our RSS feed

Blog Banner

Over the Garden Fence

Where gardeners come to find out what's happening out in the yard.

Scouting Watch: New Tomato and Potato Disease

Posted by Sarah Navrotski -


Expect to have clients calling you about a new and devastating disease to tomatoes and potatoes. Many will have read in the newspaper recently about an outbreak in the Mid-Atlantic and eastern states of Late Blight (Phytophthora infestans)—the same disease responsible for the Irish potato famine. So this is not a new disease, just a species of Phytophthora not common to Illinois in a normal year. This disease does not overwinter here, but can "blow in" during the season from other states where it does overwinter. The cool, wet conditions this season have been very conducive to its development, allowing its movement to a larger than normal area. Like Soybean Asian Rust, it does not usually make its way here in time to cause a problem in tomatoes and potatoes because conditions were not conducive—this year is potentially different. The disease is moving westward on weather patterns and just recently a late blight-infected tomato was confirmed in Northern Illinois through the UI Plant Clinic. For this reason, I have included a link to a fact sheet on Late Blight plus a few preventative fungicide control options in preparation for calls to your office.

Homeowners have a few fungicide options for protection of plants not already showing serious signs of infection. Look for fungicides labeled for tomatoes/potatoes with one of the following active ingredients. I have included a link for one example of each active ingredient, but keep in mind other brands are available depending on your location and supplier. Spray every 5-7 days unless the label states otherwise, making sure to note the Pre Harvest Interval (when to stop spraying before harvest). If clients have been spraying regularly with one of these active ingredients for control of other common tomato/potato diseases (like Septoria or Early Blight), they should continue their program for continued protection against Late Blight this season.



Fixed copper:


Feel free to contact me with further comments or questions. The UI Plant Clinic is also available until September 15 to assist in identifying or confirming disease identity There is a fee of $15.00 for each submitted sample.



Elizabeth A. Wahle, Ph.D.
Extension Specialist - Horticulture, Fruits and Vegetables
Edwardsville Extension Center
200 University Park Drive, Ste. 280
Edwardsville, Illinois 62025-3649
Ph: 618-692-9434 ext. 21
Fax: 618-692-9808

Please share this article with your friends!
Share on Facebook Tweet on Twitter