Septoria: Why Rain is Not Always a Good Thing for Growing

We've had a lot of rain in Chicago this spring/early summer (is it summer?). A lot of rain. Almost every day. We're not going to have issues with drought. Ever. All the plants we threw in the plot alongside our garage (tomatoes and cukes) seemed to be doing really poorly. The leaves were developing holes and were yellowing. I was terrified of blight, but when I went online and looked, it clearly wasn't blight. But it was another form of mold called Septoria. It's a soil-borne mildew that's especially common in areas that have high levels of rainfall and cooler temperatures.

I hustled off an email to Ask a Master Gardener in Cook County. Looking for a Master Gardener in your area? In less than a few hours, I had my response:

Hi Ann,

Thanks for sending us your question.

You are certainly correct about how cold and nasty this Spring has been! Septoria leaf spot is caused by the fungus Septoria lycopersici. High relative humidity and temperatures between 68-77 F are favorable conditions for infection and development of this disease. Though we have not been blessed with much warmth, the humidity levels have definitely been high.

Listed below are measures that can help control the disease, from Iowa State University Extension with some comments from me:

1. Plant disease-free transplants. (Since it is early in the season, you may wish to buy new seedlings at a garden center and plant them in a different area of your garden. Ask at the garden center for varietals with resistance to septoria.)
2. Space plants appropriately for good aeration.
3. Stake plants and mulch to reduce contact with the soil. (Growing tomatoes in cages is relatively effective in this respect.)
4. Do not water plants from above. The spores on infected leaves are transferred by splashing water. (Also mulch tomato plants to cover soil around them and thus also reduce the possibility of spore movement.)
5. Remove any diseased leaves to slow down infection. (Recommendation: Place any diseased leaves in the garbage; do not compost.)
6. A fungicide spray program can be used to help control the disease. Check your garden center or available fungicide products.
7. Do not work with plants during wet conditions so as not to transfer spores to other plants.
8. Control susceptible weeds such as nightshade, jimson weed, and horse nettle to reduce the amount of fungus that may overwinter. (Note: the point here is that these weeds are also hosts to the septoria spores.)
9. Clean infected garden debris in the fall and till the ground. It would also be beneficial to retill again in the spring.
10. Rotate susceptible crops. Do not grow tomatoes, peppers, or eggplants (all members of the same plant family) in that area for three years.

For more information and photos of septoria leaf spot, follow this link to the University of Illinois Extension website: http://urbanext.illinois.edu/vegproblems/problems/d_leafspot.html

For more information on gardening in general, visit our website at: http//web.extension.uiuc.edu/cook/urbanhort.html

Happy Gardening,
The University of Illinois Extension Chicago Master Gardeners

If you ever have any gardening questions, seriously, ask a Master Gardener in your area. How? Find a Master Gardener in your area. Some of the information they provided in the email above was already known to me, but it's always good to get a second opinion. So, I pulled off all of the damaged leaves (the new growth was not yet infected) and placed tomato mulch around the plants so that they wouldn't get reinfected from the soil. The only things I'm ignoring are the recommendation to plant disease-resistant varieties--there aren't really any tomato varieties that are resistant to septoria--and to treat it with a fungicide. Blech! I got to eat this stuff, you know?

So now we come to the big conundrum: crop rotation. We've planted tomatoes in the same location for three summers now but it's biting us on the rear this time. So, next summer we've got to find someplace else to plant them. The only problem is...most of the plants we grow are in the same family or carry across certain diseases even if they're not. Namely, the root vegetables are out for us. It's cheaper to buy carrots in the store than to grow them, neither of us can eat onions, and I can only eat beets sparingly (but I am learning to like them). I can't imagine growing something I can't actually eat. What's the point?

What to do? Well, I'm looking at this website. Seems to me they get it more so than other websites that give you strict guidelines about what you can and can't plant. I think the area alongside the garage will have legumes and peas and some lettuce (and maybe peanuts--hey, it's something new). But I have no idea where we're going to fit 9 tomato plants in our grow beds, especially since we can't plant them in the grow bed over against the fence (because we're planting peppers there now). I think the bed by the garage might fit 6 or so. But we'll have to find another location for the other three.

Non-gardening stuff going on? I had a nasty cold for a week and a half that settled in my chest. I think I might have either strained a muscle coughing. I'm going to the doctor tomorrow to see if they can determine which it is. So, I haven't been doing a lot of gardening lately.

On the landscape gardening front, our clematis is blooming and is gorgeous!