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Stress & 'todes

It’s always hard to follow Frank’s posts. I mean, what can I write after he applies “If it’s yellow, let it mellow” to turf disease?

The big concerns lately have been brown patch, foliar Pythium, stress, and nematodes.

While brown patch seems to have decreased somewhat from our surprise late June epidemic, I suspect that it will come surging back in with our forecasts of more heat, humidity, and rain.

Dollar spot has totally disappeared from our research plots. Too hot!

As for foliar Pythium, the rains keep coming, nighttime lows remain high, and the sites with the disease are on high alert. Most have put down one or more applications of a Pythium fungicide and are watching for new activity.

Stress? That is on the plate every week. In some recent samples, waterlogged soils have clearly caused root decline with some secondary Pythium nibbling on the aftermath. We still can’t seem to dry out in some areas.

The photo illustrates a stress problem where greens received a little too much N, got puffy, then scalped. You can see the scalped spots right at the edge where the mower hit the green.

Nematodes in turf are a tricky subject. There was a lot of discussion earlier this week amongst turf pathologists about damage thresholds in nematodes. Damage thresholds are hard to pin down, and the potential damage of a certain population of nematodes varies with the overall amount of stress at the site. Sometimes there is a correlation between turf damage and nematodes; often there is not. Usually there are multiple factors in play.

One nematode that is pretty well documented to cause damage even at low numbers is sting nematode. We picked up sting in a sample a few days ago. I heard Dr. Mike Fidanza (Penn State) joke one time, “If you want to spread news, what are the 3 best ways to do it? 1) Telephone. 2) Telegraph. 3) Tell-a-superintendent.” That is, news travels fast in this industry. After the sting finding, we had a sudden flush of requests for nematode testing because the word had gotten out. Numbers of all plant pathogenic nematodes were pretty low, and no sting nemas were detected anywhere else.

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