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Homestead observations: Vegetable health/early blight

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This article comes from the NOFA/Massachusetts 2016 October Issue Newsletter

By Sharon Gensler

Tomato plants- note green leaves all way to ground

It's the third week in September and we've been lucky that frost hasn't struck yet. It has been a hard growing year, with the drought and hotter than usual weather. As I mentioned last month, we had to resort to watering. We soaked each growing area with about an inch of water each week to augment the sparse rain. It seems that they really needed that boost to get through the stress until they could adapt. After about a month, we stopped watering, even though the drought continues. Now, the plants are thriving and still producing abundantly.

I'm especially thrilled with plant and soil health. I've been gardening most of my life and have never had such healthy plants, which I’m attributing to increased soil vitality. The years of cover cropping and attention to soil needs are paying off. I used to think that early blight was a normal/natural occurrence and not much could be done about it except to keep rain-splattered soil off plant leaves. However, at several of the NOFA/Mass soil conferences I’ve attended, I learned that Alternaria solani, the soil fungus pathogen that produces this disease, is only a “problem” to unhealthy plants.  

In fact, Alternaria is present in most soils and even on most plant leaves. It is one of the main decomposers. Without it and other decomposers, we would be buried by vegetative waste.  It is part of the complex system and web of life, which creates compost and soil. Overall it is a good-guy who is just doing its job, waiting for some vegetative material to be ready to decompose.

For example, let’s look at a tomato plant.  Very simply put, when young, a plant puts its energy into growing abundant leaves in order to increase its photosynthesizing capacity. It converts nitrogen, phosphate, potassium and many other minerals into sugars, which it uses for growth, supplying its leaves with abundant nutrients. As the plant grows taller and fruit is set and matures, more of these minerals and sugars are needed. If they are abundant in the soil, all is well. However, if plant food is limited, it “steals” these nutrients from its lower leaves to supply the new growth. The plant is trying to insure that mature fruit, and, most importantly, seeds, are produced. Thus when the lower leaves are deprived of food they become susceptible to disease. Alternaria is there waiting to do its job and decompose those sickly leaves. We label this early blight.

In the past, often by late August, most of my tomato plants have had yellow/brown leaves at the bottom. As the summer ended, the “dead zone” of defoliation rose ever higher up the plant. By late September the top third would be green and the tomatoes would be hanging from bare branches. Here at Wild Browse, this hasn’t happened for a number of years. Each year it seemed that early blight was less and less of a problem and this year, it’s been almost non-existent. Granted, Alternaria needs moisture to germinate, and this is a drought year. However, we have had abundant dew and humidity, which could have caused germination, but the healthy plants were not susceptible. Plus, early blight is rampant in many neighboring tomato plants, indicating that it has not been a blight free year.

Cucumber trellisWinter squash, cucumbers and summer squash are vegetables also susceptible to fungal disease. Powdery mildew, which is a white growth on the tops and undersides of susceptible leaves, is often prevalent by late summer. I don’t know as much about this disease except that it thrives in dry conditions. Again, to date, we have had no sign of powdery mildew. I believe that our healthy soil has been a contributing factor to our plant health. [N2] 

So, after a slow start and a lot of worry, things here have turned out to be better than expected and even better than some less worrisome years. The freezers are full, the dehydrator running non-stop, the canner waiting for more tomatoes and we have some fantastic fermented veggies to boot.

Well, the moral, if any, is soil health: increase soil fungal activity, keep the soil covered, cover crop as much as possible, use no-till methods, address soil mineral deficiencies, make and use compost, and love what you are doing!

Thought I’d share some photos from around the Wild Browse vegetable garden. Hope your growing season has been productive and enjoyable too!

Here is a recipe for the fall. Cube and steam un-ripened winter squash, green tomatoes, potatoes, and green beans, until almost cooked. Sautee onions and garlic. Prepare curry seasoning and add some thickened stock to create a gravy. Gently add vegetables, mix together and simmer until tender. Serve with sliced cucumber and yogurt.


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