Maybe you have to be a plant pathologist to appreciate a giant plastic bag of stinking cabbage. I don’t know. Let me run this by you, and you can judge for yourself.
Quicktime 5+ object
Rotating, zoomable image by Kent Loeffler
Ta da! Clubroot of cabbage. All the action here is happening below ground, which makes clubroot a sneaky disease. You might not even notice it until your precious cabbages start wilting and complaining, getting stunted, or failing to make sauerkraut-worthy heads. When you yank up your poor achievers, you find these monstrously blobby roots. By this time, you’re too late to do much, except lament your lost potential as a grower of record-breaking cabbages3.
Really, it’s best to avoid getting this disease in your garden in the first place. It’s not very common here in New York state, but when it occurs, our local experts recommend raising the soil pH by adding lime1,2. Oh, and also not growing cabbages and their pungent kin (cauliflower, Brussels sprouts, broccoli, Chinese cabbage, kohlrabi, collards…) for the next 7-10 years. Ouch.
Clubroot is a bit of an interloper here at the Mushroom Blog, since it’s not a real fungus (mycologists can be snobs about these things). However, it is a fungus-like organism, Plasmodiophora brassicae, so we’ll give it Guest Star status here. In the tree of life, it is relegated to a smallish phylum, Plasmodiophoromycota, among the great unwashed mass of protists, which need a lot more figuring out. Plasmodiophora and its ilk are enigmatic things4. They make lovely little swimmy spores, each with a flagellum like a tiny sperm. They swim around in soil water and home in on unlucky cabbage roots. Once there, they break in, and set up house as an increasingly big amoeba which we like to call a plasmodium. The presense of the plasmodium creates all kinds of trouble for the plant, inducing tumor-like clubbing, and preventing infected roots from forming their protective outer layer. That makes them vulnerable to other soil-dwelling thugs, like bacteria. Ultimately, the plasmodia form patient resting spores with tough cell walls. They can sit around in soil for up to 10 years, just waiting for you to plant another cabbage.
Perhaps it’s a particular weirdness of plant pathologists–to get excited by a good example of disease. However, it’s my private theory that the rest of you might enjoy creepily deformed stuff too. The latest issue (vol. 23) of Cabinet Magazine featured Ellen Birrell’s photos of deformed, mite-infested lemons in full page glory. These mere arthropods can hardly rival a bad case of lemon rot, but you see my point.
- Our very own Tom Zitter’s 1985 Fact Sheet on Clubroot of crucifers.
- Caldwell, B, E.B. Rosen, E. Sideman, A.M. Shelton, C.D. Smart. 2005. Resource Guide for Organic Insect and Disease Management. (Another awesome Cornell resource)
- John Evans and his Record-Breaking Vegetables. Accessed Oct 29 2006.
- J.P. Braselton. 2006. Plamodiophorid Home Page
- Protista. Wikipedia. Accessed Oct. 2006.
- M.S. Woronin. 1878. Pringsheims Jahrb. f. Wissenschaftl. Botanik 11: 548 (1877). Here is the original description of Plasmodiophora brassicae, in case you’re a geek like me.
Thanks to Mana Okhura and Dr. Chris Smart for bringing the monster to light.