Botrytis, Dog's Footprint, and Hot July Weather

Megan informed us last year that there are some edible (or drinkable) plant pathogens. I saw a few turfgrass pathogens during an early winter visit to Australia last month — some dollar spot on seashore paspalum, leaf spots on Cynodon, pink snow mold on creeping bentgrass, and the mysterious and as yet unidentified fairway patch (black fungus) disease affecting Cynodon fairways at Sydney. But my favorite disease was a drinkable one in the Barossa Valley of South Australia: the Peter Lehmann 2009 Botrytis Semillon.

Ten summers ago, before I went to grad school, I was a golf course superintendent in Japan (and during the three summers before that I was a superintendent in Shanghai). We all looked much younger then, but one thing that hasn't changed is that China and Japan remain really difficult places to grow creeping bentgrass. I'm spending most of this summer at Japan to observe golf course maintenance practices and grass performance, to collect some data, and to remember what it is like to be a golf course superintendent.

In the past week I saw some moss (above) and slime mold and dollar spot on creeping bentgrass, large patch on Zoysia japonica roughs, and the splendidly-named "dog's footprint" disease (Curvularia, below) on Zoysia matrella fairways.

Why do I say that China and Japan are really difficult places to grow creeping bentgrass? Have a look at this chart of world cities plotted by average weather data:

As we look at the average data for July, Tokyo is a little cooler than Atlanta, Osaka and Shanghai are both warmer than Atlanta, and there is less sunshine in the Asian cities than there is at Atlanta. At Atlanta you may find creeping bentgrass greens or ultradwarf bermudagrass greens. But at Shanghai, Tokyo, or Osaka, more than 95% of the greens are creeping bentgrass. It gets worse in August and September, when Shanghai, Tokyo, and Osaka all have higher average temperatures and less sunshine than Atlanta. "Change to ultradwarf bermudagrass, then, if it is so hot!", you might say, but in winter it is colder in the Asian cities than it is at Atlanta, and the annual sunshine hours in Shanghai, Tokyo, and Osaka are about 70% of what they would be at Atlanta. There is no easy answer. Here are the temperature readings I saw just before I left Japan yesterday. I'll be spending this coming week on a much cooler continent.