The Fungus Among Us


I only wish this were a column about morels or puffballs or other tasty and wonderful fungi, but it’s not.  It’s about the late blight in the gardens.

I cut seven tomato plants out of the row on low supports–they were all but one of my Principe Borgheses.  I’m thinking that the blight came on one of the volunteer plants that I transplanted into that row–but really, there’s hardly a tomato or potato plant in the garden that doesn’t have at least a few spots.

A few of the peppers and eggplant have been affected too–I also took out four sweet pepper plants while I was on my clean-up detail and I pulled a few affected leaves off the eggplants as well.

I’d been trying to figure out what I could use to help control the less severe cases–some sort of fungicide that’s not a horrible chemical I wouldn’t want on my food. So, I looked in my medicine box in the bathroom thinking about fungicides–and I found tea tree oil there.

Did a quick internet search on whether this has been tried on plants and found it has been used by grape-growers to control powdery mildew.  Good enough.

Once the severely infected plants were cut out and disposed of, I cleaned out my sprayer and mixed about a tablespoon of tea tree oil with a gallon and a half of water.  Then I sprayed down all of the plants in the row I’d taken plants out of, plus the landscape fabric beneath them, and some of the pepper and eggplant as well–especially around the areas I’d taken out plants.

I’m really not sure this will work (be warned before you try this yourself), but we’ll see.  I’m going to go in early next week and dig out all the affected potatoes as well–Australian Crescents and French Fingerlings.

Notably, the Purple Peruvian fingerlings have not had any problems with blight at all, and neither have the Nyagous black tomatoes.  Almost every other tomato in the garden has at least a little except the Stupice tomatoes on the back trellis in the northeast garden–where I’ve never grown tomatoes before.

Late blight is taking out a huge amount of the tomato crop in the northeast, as you may have heard.  We don’t usually get it until late (yes, that’s why it’s called “late blight”) if we get it at all, but this year the extremely wet July virtually guaranteed an outbreak.

I’m thinking for next year the garden across the farm on the hilltop will have to be the tomato area.  I may avoid planting potatoes altogether just to be safe.  If I do, you can be certain I’ll order certified seed instead of saving anything from this year’s crop.

However, I have read that late blight is allowed in some small measure even on certified seed potatoes–so that might not even help.  I’ll have to start looking into what regions haven’t had such a wet summer, and see if I can get seed potatoes from there.

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4 responses to this post.

  1. Yikes!

    Does this mean we may have blight in the Vermillion community garden? Lots of novices like me won’t know it when we see it, and even if we do know it, we won’t know what to do about it.

  2. Posted by flyingtomato on July 25, 2009 at 7:11 am

    Kelly–I don’t think that it’s a problem in the community garden, but I can certainly check. If it is–well, there really isn’t anything to do about it except pull plants if they get too bad. The tea tree oil is mostly just an experiment to try to keep it from spreading too much. There’s nothing to do to “cure” it once it starts–you can only try to slow the spread.

    Those Principes I pulled yesterday had several pounds of fruit apiece, but I couldn’t risk leaving the plants in to try to ripen the fruit. It’s a painful thing to sacrifice fully-loaded tomato plants!

    Carolyn–I’m going to try the tea tree oil to see if it works. Since I’m not certified organic, I am a little more flexible in what I can use. But, copper treatments can be very toxic to the applicator: http://www.extension.org/article/18351 so I’d prefer not to use them if I can avoid them!

    –re.

  3. Posted by Vines & Cattle on July 26, 2009 at 8:51 pm

    My cousin from Petaluma was in this weekend, and she thought that the organic vineyards in Napa used copper, or possibly sulfur? It’s of interest to us as we currently use chemical fungicides on the wine grapes.

  4. Posted by flyingtomato on July 27, 2009 at 10:11 am

    From my reading, copper sulfate is one of the chemical inputs that is approved in organic production–and mostly for this reason (organic grape growing). But, it seems only to be approved as a “last ditch” for fungal diseases–after you’ve tried everything else. My gut tells me that organic growers with a lot at stake economically aren’t going to hem and haw about using it if it’s the only thing that’s really been shown to work–after all, blight can take hold pretty quickly, so why would a big grower take the risk of using something not as effective for awhile when blight was getting going?

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