Precipitation across much of Japan has been above average this year, and it is no surprise then to be seeing two diseases that are associated with wet growing conditions: large patch (Rhizoctonia solani) and yellow tuft (Sclerophthora macrospora). I’ve seen yellow tuft on creeping bentgrass all over Japan and I’ve seen a lot of suspected yellow tuft on korai (Zoysia matrella) fairways as well.

The plant at left is a normal Zoysia matrella from a fairway at Okinawa, while the plant at right is showing the abnormal tillering or “witch’s broom” symptoms that are typical of yellow tuft. I had thought that this might be a type of mite damage, which we sometimes see on this grass, but after repeatedly seeing these yellow tuft symptoms most prolific in wet areas, I’ve disabused myself of that suspicion.

At golf courses that do not apply preventative fungicides for large patch, symptoms are starting to appear. I notice again a clear distinction between the large patch severity on Zoysia japonica and Zoysia matrella, which I have written about before, and if you will humour me I will show a few photos below that are illustrative of the relative susceptibility of Zoysia japonica to large patch compared with the relative resistance of Zoysia matrella.

Above we see two mowing heights, fairway height at left, and rough height at right, and the patch is relatively uniform on this Zoysia japonica at both mowing heights. This golf course in West Japan has primarily Zoysia matrella fairways, but in this area the Zoysia japonica from the rough has encroached. We can see that large patch thrives in Zoysia japonica at fairway height.

The image above is in a location where the Zoysia japonica has encroached into a Zoysia matrella fairway and where Zoysia japonica dominates the sward, large patch thrives. When we look at the point where Zoysia matrella still dominates the sward, below, we see that the disease symptoms cease, and are only evident on the Zoysia japonica.

For more pictures of large patch, yellow tuft, and lots of images of Zoysia japonica and Zoysia matrella at Japan, including numerous images of Zoysia matrella greens, see this photo gallery on my Flickr page.