Normally, I enjoy the challenges of growing my own food. My tomatoes survived an early pruning by the ground hog that lives under my deck and significant defoliation by tobacco worms this year. I've come to expect the slow progression of early blight each season. The problem with late blight (as the name implies) is it doesn't appear until your tomatoes are doing so well you start to wonder if the supports will handle the weight of a multitude of green tomatoes. You begin to think you're home free, but the next thing you know, you're ripping out plants and tossing out tomatoes that will never ripen.
I know I'm not alone this year - the number one call at the local Master Gardener hotline in August was "What do I do about the blight?" Since one can be managed (early blight) and the other (late blight) is a swift death sentence, it's important to know which one you have. Luckily, the first symptoms appear in different places and are easy to distiinguish.
Early blight shows up as tiny brown spots on the lower leaves and progresses slowly up the plant. Eventually, the spots will get larger and the stems and fruit will be affected, but if you remove infected leaves as they appear, it's still possible to harvest a crop of vine-ripened tomatoes. If you are curious, take a close look at the larger leaf spots and you will see a pattern of concentric rings within each spot. (Think bulls-eye or ripples in a pond...)
Early Blight - early on
Late blight first appears as a "water-soaked" blotch on leaves (anywhere on the plant) and progresses rapidly to large dark brown spots on leaves and stems. A "water mark" is harder to see, but it's a symptom you'll never miss once you've seen it. If conditions are favorable, the blotches grow and tissue dies - eventually fruit starts to rot. Just a few days after the first symptoms, the plant is so affected that you will realize there's no salvaging this crop.
Late Blight - early water marks
Late Blight - more severe
Late Blight - worse
Both diseases can be prevented with an appropriate fungicide labeled for use on food crops. The critical point is that this treatment is "preventative" not "curative". It must be in place and covering all plant surfaces before fungal spores land. If not, infection will occur as soon as the weather cooperates. (Early blight likes it hot, wet and humid while late blight thrives during cooler, wet summer weather.)
As for "topiary tomatoes, that's the name I gave the one Roma tomato I planted this year because (if you don't look too closely) you'd think it was pruned in topiary style. The reality is that early blight foliage removal inadvertently results in this form. "Health Kick" was a spur of the moment pick at the greenhouse this spring. While it's more susceptible to early blight than the older "Celebrity" tomatoes I grew, I was able to harvest over 30 Roma tomatoes from one plant before early blight won. All Roma tomatoes have a natural resistance to late blight. So for now at least, I know I'll plant another Roma tomato and have time to see if my attitude changes about growing the others over the coming winter.
Topiary tomato - Early Blight on Roma tomato
