Salem Community Gardens

UMass Extension Agriculture and Landscape Program, June 29, 2009:

Late Blight on Tomato and Potatoes [and Eggplant]

Garden retailers and landscapers should be aware of Late Blight caused by Phytophthora infestans – a very destructive and very infectious disease that kills tomato and potato plants in gardens and on commercial farms in the eastern U.S.

Late blight is the same disease that caused the Irish Potato Famine in the 1840s. It has been in the US for over a century, but it has never occurred this early and this widespread. It not only threatens home gardens, but also the thousands of acres of commercial potatoes and tomatoes that are grown in Massachusetts and across New England. The disease has been diagnosed on tomato transplants throughout the Northeast. Infected plants were distributed throughout the region by several plant retailers this spring. This disease is not seed borne however, it is exceptionally contagious, and can spread to tomato plants on retail shelves not involved in the original and initial source of the inoculum.

Late blight, affects both potato and tomato crops. It produces spores very rapidly and these move very easily from one garden or field to others, because the spores are easily carried in wind currents to infect susceptible plants in even the most remote area in our region.  All tomato and potato plants grown in home gardens and in commercial fields are susceptible to late blight! 

What to Look For

The most common early symptoms on tomato transplants are brown lesions on stems, with white fungal growth developing under moist conditions.

Symptoms appear as large (at least nickel-sized) olive-green to brown spots on leaves with slightly fuzzy white fungal growth on the underside when conditions have been humid or wet. Sometimes the lesion border is yellow or has a water-soaked appearance. Leaf lesions begin as tiny, irregularly shaped brown spots. Brown to blackish lesions also develop on upper stems. Firm, brown spots develop on tomato fruit. Late blight can be confused with early blight and Septoria leaf spot, two common diseases found in home gardens.  If the lesion has a yellow border and is occurring on the bottom of the plant, it is likely due to infection of either early blight or Septoria leaf spot.

Photo gallery of what to look for:

http://www.hort.cornell.edu/department/Facilities/lihrec/vegpath/photos/lateblight_tomato.htm
http://blogs.cornell.edu/hort/2009/06/26/late-blight-a-serious-disease-killing-tomatoes-and-potatoes-this-year/

In an effort to improve communication and maintain a positive environment for all gardeners, SCG board has created the position of garden captain. These volunteers serve on the SCG board and have a plot in the garden that they represent. They watch for abandoned gardens, and should be made aware of any issues, concerns, or suggestions you may have pertaining to the gardens. This year’s garden captains are: Shannon Bott at Mack Park, and William Hanger at Palmer Cove. You can reach then by e-mail, phone, or leave them a note in the garden mailbox.
Shannon Bott (Mack Park) 978-375-1953  This e-mail address is being protected from spambots. You need JavaScript enabled to view it
William Hanger (Palmer Cove) 978-594-0855  This e-mail address is being protected from spambots. You need JavaScript enabled to view it

In response to record-long waiting lists and an ever-growing interest, Salem Community Gardens is seeking to establish new gardens for next summer. Potential sites include Collins Cove and Forest River Park (see map at right). We are excited about the prospect but there is much work to be done! If you would like to become involved with the planning and organization or would just like to express your interest and enthusiasm, please contact Lisa ( This e-mail address is being protected from spambots. You need JavaScript enabled to view it ) or Leslie ( This e-mail address is being protected from spambots. You need JavaScript enabled to view it ).