Who says there’s no disease?

What happens when you send in a stunted or wilted turf sample and the report comes back negative for disease?

That is not all that uncommon, says Jim Kerns, Ph.D., assistant professor and extension specialist in plant pathology at North Carolina State University.

Of 400 bentgrass samples that came through the NCSU lab in 2013, a full 51 percent had no disease. In fact, root rot was the top disease diagnosis at the lab…and it was found on fewer than one-fifth of the samples submitted.

The figure for samples with no disease at all was 26 percent on Bermudagrass. That figures to more clean samples than the top disease diagnosed: leaf spot, which was found on 24 percent of samples.

What’s going on?

Part of the reason may be due to the way superintendents collect samples, Kerns figures. “Collect samples before you spray,” he begs. “The green will not die in the hour or two it takes you to take and bag a sample.” However, spraying first and coming back a couple of hours later may be enough to destroy the pathogen or lower its presence below critical mass.

Even on highly managed greens in mid-Summer, reports of “no disease” are not all that infrequent. “Diseases are not that common,” he adds.

If there is a positive diagnosis, don’t expect instant gratification. “It takes time for turf to recover from diseases when it is hot – especially the cool-season grasses. Fungicides take three to seven days to work,” Kerns says. For that reason, he recommends marking a disease ring to make it easier to evaluate whether the application controlled the disease.