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:
- Get great close-up views of late blight tomato infections
- Images of infected plants from 2009
- Info for organic growers from CT NOFA
- Vegetable MD – tomato diseases
- Sign up for a webinar on late blight management for organic farms, planned for July 1, 2010
Don’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.