I’m spending this month at Ishigaki, located in the far south of Japan in the Ryukyu Islands. In fact, I’m a little south of Taipei, at the same latitude as Key West, Florida. Located at the boundary between the East China Sea and the Philippine Sea, these islands have a climate more similar to that of Hanoi, Hong Kong, or Haikou than they do to Hiroshima or other cities on the main Japanese island of Honshu.
And that is what brings me here, to study the weather and to study the grasses. More about the weather, and an obligatory mention of a couple turfgrass diseases, a little later. First, let’s have a look around, and see what grasses we can find.
Manilagrass (Zoysia matrella) is the grass here, as it is in so much of these tropical areas of East and Southeast Asia. When Dr. John Kaminski was over earlier this year for the Asian Turfgrass Roadshow, we saw manilagrass thriving, first at Sentosa GC in Singapore, then at Thana City GC in Bangkok, then at Wack Wack Golf and CC in Manila, and then again at the stunning Clearwater Bay Golf and CC in Hong Kong. In the video above, and in this video from another island, we see that manilagrass can tolerate salinity, and it can also tolerate dry conditions, and we see that it tends, even in wild types, to have a fine leaf blade.
Manilagrass should be used more in Southeast Asia. It performs well here, being naturally adapted to the rainy season with its associated low light intensity, and also to the dry season. A grass that has been overused in Southeast Asia over the past decade is seashore paspalum (Paspalum vaginatum). As we can see from the video, the natural environment of manilagrass is areas that are subject to drought, while seashore paspalum is a grass that grows in tidal swamps.
Turning to the weather, what is so interesting about these islands that would make me want to spend a month here? Well, at this time of year it is quite salubrious, with July and August having (for the city of Naha in Okinawa) the highest average sunshine (sunshine duration is defined as the period of time when of the direct solar irradiance is greater than 120 W m-2) of the entire year, July on average with 239 hours, and August coming in second with 215 hours. But if we compare that to the climatological normals for Miami, there are eight months of the year at Miami with more than 239 hours average sunshine duration, and all twelve months of the year at Miami have more than 215 hours of sunshine. Essentially, the months with the most light here are equivalent to the months with the least amount of light in Miami.
The green line shows the Naha data from this year, and there was a peak in mid-July just over eight hours sunshine duration per day, but it has dropped now with a few typhoons passing through in early and mid-August. I don’t have access to daily data for Miami, but the climatological normals for Miami are for more than eight hours of daily sunshine from March through October. That difference in sunshine duration represents a huge amount of photosynthetic irradiance that reaches grass in south Florida, but it doesn’t reach grass at the same latitude in East Asia.
And what about turfgrass diseases? Well, I’ve just seen two this month. Pictured below is curvularia blight on a manilagrass fairway in Okinawa. This disease has the delightful name of “dog’s footprint” in Japanese. And I also saw bermudagrass white leaf, on its eponymous host, also at Okinawa.
I’ve otherwise been studying grasses and studying the weather, trying to learn more about which grasses perform best in which types of environments, and drawing inferences about what management practices will assist in produce the best-performing turfgrass surfaces.