So a day or two ago I was innocently researching away about compost and just for fun, hit the Google ‘scholar’ option to see what came up under the wide-open search term “compost.” (Toe surgery confines me for the moment to whatever I can find on the Internet; even the University library six blocks away is too far).
Lo and behold, I found myself looking at a number of articles dating back to the eighties and continuing right up to the present day about managing diseases with compost. Slap my ass and call me Judy, but I never heard of such a thing. Like a good metaphor, however, it makes sense as soon as I hear it: so many plant diseases are soil-borne that changing the soil balance would reasonably affect disease contraction, severity, and so on.
A recent study conducted in Greece found that freshly cured compost (stuff that had finished decomposing, but hadn’t sat around long afterwards) helped suppress Phytophthora nicotianae Breda de Haan, a.k.a. “black shank”—a surprisingly vivid descriptor and quite apt, since this is what a stem looks like after it hits:
In this study, nine different composts were tested, all derived from local agri-businesses such as olive-oil and wine. Though aged composts were far less effective, all of the just-cured composts "demonstrated high levels of suppressiveness against Phytophthora nicotianae Breda de Haan in tomato." They didn't improve things "a little," or "somewhat;" they had what the study abstract calls a "“general suppression phenomenon," decreasing disease incidence by 81 to 100%. Wow.
P. nicotianae is truly an equal opportunity disease, discriminating neither by plant, plant part, or world region. Though primarily considered a root and "collar" disease, it also affects stems, fruit, and leaves, as these photos show. Google it, and you’ll see reports about its impact on tomatoes, tobacco, eucalyptus, basil, and thyme, amongst others.
Best of all, this come-one, come-all charmer seems to be making a world tour: it first appeared in tomatoes in Australia in 1986, showed up in South African eucalyptus in 1999, has been making inroads in Chilean tomato fields for five years or so, and who knows, may be appearing in a field near you soon.
So anything that helps control it is hugely important and helpful.
Now, I call that interesting.
Let’s hear it for organic disease-control!