I want to tell you all about my lovely June garden… I want to post beautifully composed photos of the peas going gangbusters, of the fresh strawberries we pick to sweeten our morning cereal, the lovely green beans in full flower, and the prairie forbes just opening their petals to the sky.
But tell the truth and shame the Devil, my Grandma Juanita used to say. I’m a sho’ nuff knotty-headed organic gardener and I’ve got to tell it like it is. Something is going on in my garden this year, something that puts the “ugh” in an ugly garden. Brace yourselves.
THIS is the truth of what is going on in my garden this year. This ugly, sickly, disease-spotted wreck of a leaf. Yeppers, my entire tomato and pepper crop has contracted – in varying degrees — bacterial spot. In case you’re not familiar, bacterial spot is a serious disease caused by several species of organisms in the Xanthomomas family. Xanthomomas will attack any and all plants in the nightshade family, the most common of which are tomatoes, peppers, potatoes, and egg-plants. You shouldn’t be surprised that I’m grinding my teeth, grumbling, and shaking my finger in God’s face. I’ve got to figure out what to do. What caused the outbreak? Should I intervene? If so, how and how strongly?
First, let’s everybody get on the same page about bacterial spot. What does it look like? How do you recognize it?
It isn’t so very difficult. This disease is so common that you’ve probably seen it, even if you didn’t quite know what you were looking at. While the disease can manifest in any part of the plant (stems, foliage, blossoms or fruits), early signs are usually found in the leaves (thus its common name, bacterial leaf-spot). You’ll probably notice tiny yellow-greenish spots on the leaves, mostly likely on the leaf margins. These will rapidly expand to a triangular shape (hemmed in by the vascular structure of the leaf); this tissue will become necrotic, and blacken. Eventually, infected leaves fall off, and spread the disease pathogen into the soil. A sure diagnosis of advanced bacterial spot in pepper plants is a tall leggy plant with leaves at the crown, and none along the lower stem (tomato leaves infected with bacterial spot are less likely to fall off, so be careful to differentiate these symptoms between the two species).
Bacterial spot can be indigenous in soil. It can spread to soil in which infected plant parts have decomposed. It can be vectored on contaminated seed, and it is spread by water: splashing raindrops, overhead watering, over-watering, by insufficient air circulation among closely crowded plants. You can bring it home from a nursery, save it in your own seed, or have it thriving in your own soil.
It is important to mitigate any knee-jerk response you may have to the presence of this disease (“ahhhh! My plant has leaf spot!!!) with the realization that some plants catch it and get over it, some plants catch it and tolerate it, and some plants catch it and drop dead. Whether or not your plant succumbs depends on a complex interplay of weather conditions, choiceful chemical intervention, garden hygiene, and each plant’s individual constitution.
Organic gardening is always about choices, and about weighing risk-to-outcome-to-cost ratios. For me, one key issue that guides how I proceed is how I think the plant most likely caught the disease. This will tell me something about the likelihood of the plant surviving the disease with or without intervention.
Disease sleuthing is the work of the organic ecosystemer. Let’s get on the prowl…
1) I planted out all of my tomatoes, and peppers on the same day in mid-May. All of them began to show signs of infection within a week of planting.
2) The weather was in the optimum range for the proliferation of the disease, between 60 – 80 degrees Fahrenheit; and worse, it has rained, more or less, every other day since I planted them out. It has rained so much that I still have not (by mid-June) laid out my soaker hoses!
3) I planted the tomatoes in last year’s tomato bed. Did this year’s tomatoes catch the disease from last year’s soil (i.e. should I have rotated the crop)? I didn’t have bacterial spot in my tomatoes last year, despite the long wet spring. So probably not.
4) I planted the cayennes and chili peppers in the raised beds where I had planted peppers last year. Did they catch the disease from last year’s soil (i.e. should I have rotated the crop)? I didn’t have bacterial spot in my pepper plants last year, despite the long wet spring. So probably not.
5) I planted the sweet bell peppers and the poblano peppers where I grew corn last year (in short, I rotated this crop). There shouldn’t be any soil-born contamination between these two crops. Of course, the soil could have contained the bacterial already; there just isn’t any way to tell.
Because I had no bacterial spot in my garden last year whatsoever, because there was no difference between replanting in the same spot or planting in a new spot, and most critically, because all of my plants showed symptoms of the disease at exactly the same time, I’m thinking I probably imported the disease from the nursery. The cool, wet conditions in my garden were also perfect for rapid disease proliferation.
1) I responded to the presence of the disease by first removing and discarding any leaves that showed symptoms. I then treated all of the plants with a single application of copper fungicide, mixed with insecticidal soap and neem oil. I added the soap and neem oil to repel insects that might be attracted to the stressed plants.
2) By June 1, all signs of the disease in the tomato plants had disappeared.
3) By June 1, the cayenne and chili peppers planted in the raised beds showed neither improvement nor worsening.
4) By June 1, the sweet bell and poblano peppers were slouching their way closer to an ignominious, and perhaps inevitable death.
What I’m thinking:
1) The tomato varieties I chose may have responded to the copper fungicide treatment better than the peppers did because they, themselves, are partially resistant to the disease. I planted heirloom varieties; but even heirlooms – not selected with disease resistance in mind – have some indigenous disease resistance.
2) All four varieties of pepper plants (unlike the tomatoes) may be particularly susceptible to bacterial spot. Again, these are heirloom varieties, not selected for disease resistance.
3) The peppers in the raised beds responded to the treatment better than their ground-planted cousins because superior drainage conditions allowed drying of the plants between rainstorms. Oppositely, the peppers planted in the ground sickened despite treatment because of the poor soil drainage.
1) I can continue to treat all tomatoes and all peppers with copper fungicide for this gardening season, and then rotate the crop next year. Continued treatment will provide prophylaxis for the tomato plants should weather conditions continue to favor the disease, and will help to mitigate the continued presence of the disease in the pepper crop.
2) I can cease copper fungicide treatment of the tomato crop, especially because I anticipate warmer, drier weather conditions in June and July, but continue copper fungicide treatment of the entire pepper crop, which still shows sign of disease stress.
3) I can cease copper fungicide treatment of the tomato, cayenne and chili crops, but continue treating the sweet bell and poblano crops, which are the worst effected.
4) I can cease treating all of my nightshade crops with copper fungicide and rely on the coming warmer and drier June/July weather to slow the process of the disease.
My best organic ecosystemic sense tells me:
1) Copper fungicide is one of the most toxic chemical interventions in the organic gardener’s arsenal. It lingers in the environment. It is dangerous to fish. It is dangerous to birds. It is dangerous to mammals. It is dangerous to me. I use it very rarely, most often when trying to prevent total crop loss by fungal disease in fruit crops. Furthermore, it is best used in prophylaxis. You spray it before disease shows up. It is much less effective if used afterward.
2) If I’ve guessed correctly that the peppers are susceptible to the disease, knowing that the drainage around the sweet bell and poblano crops is poor, it only makes sense to conclude that spraying copper fungicide repeatedly is a waste copper fungicide. I will dig these plants up, discard them, and replant new ones in one of the raised beds. I certainly won’t plant peppers or tomatoes in the same location next year until I’ve built raised beds there.
3) Because the weather is going to warm up and dry out as June turns into July, I’m just not worried enough about my tomato plants to treat them with copper fungicide again. The disease may reappear if June and July weather conditions don’t improve; but with excellent garden hygiene, sufficient fertilizer and a prayer or two, the plants can tolerate a mild to moderate infection with minimal crop loss. I have 15 plants, for Pete’s sake. Surely that’s enough to satisfy my family, even if the crop is reduced?
4) I will also cease to spray the chili and cayenne peppers, as they seem to be holding their own so far in the raised bed. I will certainly rotate nightshade plants out of this raised bed next year to prevent the build up of the disease pathogen in the soil.
I am, by constitution, somewhat anti-interventionist when it comes to managing garden pests. In this case, the risk-to-outcome ratio doesn’t, to my mind, justify the continued use of a highly toxic chemical intervention. I’ll keep you posted on the progress of the situation. I’m curious how others out there have responded to similar garden troubles.