Late Blight – The Sequel

It’s baaack … Connecticut Agricultural Experiment Station (CAES)recently issued the following:

-Alert for Late Blight of Tomato and Potato-

Late blight was identified on tomato plants from New Haven County on Thursday, 17 June 2010.  If you think you have seen late blight in your greenhouse, garden, or on volunteer potato plants, please contact The Plant Disease Information Office (203.974.8601).  You can also send or bring in samples for diagnosis.

Here’s a quick synopsis of the CAES late blight fact sheet:

This year tomatoes and potatoes are at high risk for  Phytophthora infestans (phyto is Greek for plant and phthora means destroyer), aka late blight, because of 2009’s widespread outbreak throughout Connecticut and the northeast. P. infestans overwinters in potato tubers.  Heavy rains, overhead watering, and soil disruption transports the pathogen to new plants. Infection becomes visible in 3 to 5 days and continues to grow at an alarming rate. Each individual lesion produces from 100,000 to 300,000 sporangia per day and each of these tiny buggers can go on to infect anew. Late blight can also infect other Solanaceae plants (eggplant and peppers for example) and ornamental hybrid petunias. Wind-blown sporangia can travel many, many miles.

CT’s Ag Station says the pathogen does not survive in soil, plant debris, or in tomato seeds. But when I listened in on a  2009 late blight teleconference by Cornell scientists they said late blight can survive in soils for as long as 8 years.  Either way, this is one plant destroya that lives up to its name – late blight is not to be messed with. Stopping/controlling it requires daily plant inspections and immediate removal and destruction (in sealed plastic bags) of all plant material. DO NOT COMPOST infected plants or fruit. I have not yet found a clear answer as to whether it is ok to burn infected plants in an outdoor fire pit. Please respond here if you know the answer.

Olive brown lesions on plant stems, 1/2 to 3/4 inch olive brown lesions – some with yellow margins – on leaves, and dark brown, rapidly expanding lesions on fruit are all signs of late blight. Similar fungal diseases on tomatoes  include Septoria lycopersici leaf spot, usually on lower leaves which then turn yellow and drop off, (I have leaf spot every year) and early blight, Alternaria solani, which causes dark brown/black 1/2 inch dead spots that enlarge to concentric rings (a bull’s eye). Follow this link for photos of tomatoes infected with late blight, Septoria, and early blight, and to read the entire tomato blight fact sheet.

More late blight info:

tomato1Don’t think you are safe because you missed last year’s outbreak and grew your plants from seed. An alert from CT NOFA (Northeast Organic Farming Association) confirms late blight in a backyard garden with no previous late blight problems and in tomatoes home-grown from seed. After a quick check in my gardens I can breath a brief sigh of relief – my tomatoes, so far, look healthy. Cherry tomatoes are beginning to fruit, and Pruden’s Purple, Roma, and Manyel plants are all in flower. But you can be sure I will check them daily for signs of late blight.

5 comments for “Late Blight – The Sequel

  1. June 25, 2010 at 8:56 am

    Thanks for the update…sounds like deja vu all over again. Unfortunately.

  2. June 28, 2010 at 9:04 pm

    It’s so frustrating to hear that late blight is back again this year; we had almost no tomatoes here last year. I think it’s particularly problematic when late blight is in back yard gardens because many back yard gardeners may not recognize it, know what to do about it, or understand that the infection can spread some distance to other gardens and farms. It only takes one gardener who decides to ignore the problem with their tomato plants to wipe out the crop in an entire community.

  3. joenesgarden
    June 29, 2010 at 7:13 am

    You are, of course, correct Jean. The only way to spread the info is to continue to mention it on blogs, through the media, and word-of-mouth.

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