I've recently had a number of calls concerning an increasing amount of leaf blotch on strawberry. This makes sense, since we've had continuing rains and the subsequent lengthy periods of free moisture coupled with the warming weather ideal for propogation of this pathogen.
For those unfamiliar with this disease, it is caused by the fungal pathogen Zythia fragaraiae. The disease appears as tan to gray blotches often occurring at the margins of the leaves, and one tends to see more disease on the older leaves than the younger ones. The blotches are irregular in shape and can cover pretty well the whole leaf and spread to the fruit calyces in advanced cases. A diagnostic feature of the disease are tiny brown to black fruiting bodies nestled within the blotches. These are the fruiting bodies of the pathogen which produce the spores to spread the disease around.
The call has always been that this is a minor disease, and not worthy of taking any action beyond keeping an eye on it. Personally, outside of minor marketable fruit loss to the unsightly brown calyces, I have yet to see major plant damage, much less total plant loss to this pathogen. That is not to say that it won't happen, and our new small fruit plant pathologist Akif Eskalen asks that I mention here how a minor disease could get to be a major issue when the right environmental conditions come up, that is to say, this year.
I couldn't agree more with Akif that the problem of leaf blotch could someday and sometime be serious, so we are developing a competence on it. Akif already has a bunch of Zythia samples that I sent to his laboratory for fungicide sensitivity analysis (in other words which materials offer promise and which ones don't). Currently he has them ID'd by DNA analysis and will soon proceed to test them.
So, while I still would not be overly concerned about Zythia on strawberry right now, it nevertheless serves our purposes to be ready should it ever be a problem. And that is exactly what we are doing.
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