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Preventing tomato blights in wet climates

Tomato alleyTomatoes can be some of the easiest vegetables to grow, but only if you have a long, hot (but not too hot), dry (but not too dry) growing season.  We struggle with tomatoes in non-drought years because our seemingly endless rains breed fungi that take out our crops.  I've posted about preventing tomato blights in bits and pieces before, but I thought I'd pull all of our anti-blight measures together into one post to make it easier for you to follow along.

Plant your tomatoes in the sunniest spot.  This year, we made an extra bed running the length of the chicken pasture just for our tomatoes.  The fence line runs from east to west on the most northern side of the yard, so this location gets the least shade from the hillside and the plants are least likely to shade each other.  The only slight problem with this setup is that grasses on the pasture side of the fence poke through the chicken wire, but they don't seem to bother the tomatoes and I yank them out when I weed.

Space the tomatoes far apart.  The distance you choose to provide between your tomato plants will depend on your pruning method, but the goal is to make sure there's open air between them.  We prune to three main stalks and tie the plants to a stake, so we only need about three feet between plants.  If you've got space, more room is always better.

Stake your tomatoes.  You may be starting to notice that all of these techniques have a common theme --- keeping the leaves of the tomatoes dry.  It's a big no-no to let your tomatoes sprawl across the ground since they'll take much longer to dry off after a rain or even a heavy dew.  Cages are okay, but hinder air circulation.  We tie up our tomatoes once a week to keep them climbing their stake.

Early blightPrune relentlessly.  Blight spores splash up from the ground onto tomato leaves, where the fungi grow and reproduce, producing more spores than can spread through your whole patch.  As soon as the tomatoes are about eight inches tall, I cut off any leaves touching the ground, a process that I repeat weekly since the higher leaves will start to bend down as they grow older.  Meanwhile, I snip off any signs of incipient fungal damage --- early blight showed up at the beginning of July, but with constant leaf removal, seems to be in check.  Finally, I remove all suckers, leaving only three main stems.  When pruning, clean your clippers with an alcohol-soaked rag between each plant and after you cut any dicey-looking foliage.  It's okay to let healthy leaves and stems fall to the ground, but take diseased leaves as far away as possible or burn them.  If a plant seems to be nearly all diseased, rip the whole thing out ASAP rather than hoping you can baby it back to life.

Choose resistant varieties.  We've tried out dozens of tomato varieties, but now focus on ones that are a bit more resistant than normal to early blight, late blight, and septoria leaf spot (our three main problems.)  None of these tomatoes are entirely immune, though, so we can't ignore them and hope for the best.

Water from below and/or in the early morning.  If you have to get the leaves of your tomatoes wet, make sure you do it first thing in the morning on a sunny day so that the plants will dry off as soon as possible.  I've located our sprinklers so that they don't hit the main tomato area, but we haven't got our drip irrigation installed yet.  The plants seem to be doing fine without the extra water so far.

Martino's RomaRace the blight.  Of our three main fungal diseases, late blight is the real doozy, and it tends to hit late in the season just as the name suggests.  For fresh eating, it would be great to have ripe tomatoes all summer, but if you put away a lot of sauces, it wouldn't hurt to try out some determinate tomatoes.  This year, over half of our total tomato planting is devoted to Martino's Roma, which will drown you in tomatoes for a month or two and then peter out.  Another facet of racing the blight is to make sure your plants are always growing as fast as possible by providing lots of manure and not starting the seedlings too early (allowing them to be stunted.)

And now, two blight prevention tactics that we've tried which have failed miserably:

Ripening romaDespite lots of rain, we seem to be in great tomato shape this year.  We ate 2011's first tomato (a Stupice) on July 12 and have enjoyed a tomato every other day since.  The main crop is about to come in, at which point I'll be preserving as fast as possible and quickly forgetting that a sun-ripened tomato is a rare treat.

Our chicken waterer is always poop-free.


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Anna - what resistant varieties do you grow, other than the ones you mentioned (Martino's Roma and Stupice)? Neither of which I have heard of BTW :-)
Comment by De Tue Jul 19 08:03:15 2011

We haven't made a great effort to hunt down specifically resistant varieties because it seems like the ones that are resistant to one fungus are quite susceptible to another. However, any varieties that repeatedly succumb to something get deleted from our planting list.

Here are the tomatoes we're growing this year with a note on any special resistance I've noticed:

  • Yellow Roma - an indeterminate to extend our roma season. Seems a bit more resistant to early blight than Martino's Roma is, but doesn't set as many fruits as early, so overall yields tend to be lower (especially if late blight hits.)

  • Martino's Roma - more resistant to late blight than the bigger romas we'd tried (Russian Roma, San Marzano)

  • Blondkopfchen - no real resistance, but we like the sweet, tiny, very copious yellow fruits

  • Ken's red - a good slicer.

  • Crazy - resistant to late blight. Also, our second earliest tomato to fruit most years

  • Early pick - Despite the name, doesn't seem as early as Crazy and Stupice. Can't remember its resistance, but it wasn't awful. Good slicer.

  • Stupice - Our earliest tomato, and pretty resistant to early blight and septoria leaf spot.

Comment by anna Tue Jul 19 11:47:59 2011
Here we grow tomatoes under a plastic cover until the rainy season ends, but sometimes after that as well. I built a 8 foot high, 8 foot wide hoop tunnel out of bamboo, and covered just the top with a plastic sheet. They get plenty of air movement through the open sides, and rain doesn't fall on them. Works great so far. The plants are well mulched and staked along the sides. Of course, typhoon season is now upon us...
Comment by Eric Burke Wed Jul 20 00:30:56 2011
Good point --- if we were really desperate, we'd have to resort to a hoop house. Luckily, we seem to be just dry enough that we can get away without, although from what I read, in the Pacific Northwest, you can't hope for a homegrown tomato otherwise. I like your homemade hoop house design!
Comment by anna Wed Jul 20 08:04:45 2011