Watch out For Blight!
I got a very sad email the other day from Don Kretschmann, the farmer who runs the CSA I belong to:
“Late blight is here and is devestating the tomatoes just as we are making the first major picking of our largest field. the slightly smaller second field is now also showing signs of phytophthora infestans. We’ve experienced late blight before, but never this early in the season. It’s very discouraging to look forward toa nearly tomato-less season. But we are not alone. the wet 2009 season has provided nearly perfect conditions for the fungus….”
What exactly is this fungus? If I’d been paying closer attention to the Post-Gazette on July 11, I would have seen this column by Sandy Feather and I would already have known that “the fungus Phytopthora infestans, late blight[,] is highly contagious and can wipe out tomato and potato crops in short order. It is the disease responsible for the potato famine in Ireland in the mid-1800s.”
Scary stuff, especially since “During moist weather, the spores can survive and be transported up to 50 miles on air currents to infect other plantings of tomatoes and potatoes. During favorable weather conditions, unprotected foliage can be infected in three to six hours; symptoms can appear within a week. Those symptoms can expand rapidly during cool, wet weather and cause entire plantings to die within two weeks of infection.”
Unfortunately, the only foolproof way to fight it, according to Ms. Feather, is fungicide application, a procedure that I will not institute in my garden. I suppose I should take Ms. Feather’s advice and both trim and bury any infected portions I discover on my plants; though I wonder how burying the leaves will necessarily be any safer than sending them to the landfill: I’m just as likely to dig up that spot in my yard at some point in the future to garden there.
I suppose it’s too late to hope for hot and dry weather this year. I guess I’ll just play defense and hope to get a few more tomatoes from my yard, even if I won’t be making any huge batches of soup.
I have an email in to Ms. Feather and anotehr in to Don Kretschmann asking if either can suggest some more sustainable measures than fungicide applications to control the disease; in the meantime, if anyone else has some tips to help us get the most out of our gardens, please let us know!
August 14th, 2009 at 12:36 pm
Thanks to Farmer Troy for a great link to a late blight FAQ:
http://www.umassgreeninfo.org/homegarden/pdf/late_blight_faq_09.pdf
August 14th, 2009 at 12:40 pm
And from Sandy Feather:
There are products that are labeled for organic production such as copper-based fungicides, biological fungicides such as Serenade and even potassium bicarbonate.
If you are not willing to spray even these materials, when we have outbreaks of disease such as late blight on tomatoes and potatoes or downy mildew on cucurbit crops, you are at risk for losing the entire crop.
[Other strategies include] selecting resistant varieties when available; practicing crop rotation, even in a small area; fertilizing based on soil test results; and protecting crops from drought stress and insect damage as the most important cultural controls. Late blight can only overwinter in our climate on potatoes that were infected and overlooked during harvest. It does not overwinter in your garden if you only grow tomatoes.
Best regards,
Sandy
August 14th, 2009 at 2:34 pm
Jesse,
According to my Penn State Extension Agent, do not bury (or compost) any infected plant materials. Instead remove the infected plants carefully and put them into a plastic garbage bag, and put them out with the trash. Otherwise you may run the risk of spreading the microbes into the surrounding soil.
August 14th, 2009 at 3:37 pm
& from Don Kretschmann:
I’d just take the science and research for what it says, prophylactic is the
only way. It is problematic for us organic growers because the copper
organic spray is one of the most harsh we can use, perhaps worse than the
chemical fungicides. If we don’t have a problem, why use it at all. If we
wait for the problem (late blight) it’s already too late to use the spray.
Catch 22. So far my experience this hear says that the preventative spray
has helped. The other field where I waited, is almost totally infected.
–Don
August 16th, 2009 at 10:02 am
Story in today’s Post Gazette about Late-Blight . . .
http://www.post-gazette.com/pg/09228/991203-455.stm
I hyper-linked it into my name (above) for quick linking . . .
Farmer Troy