2020 Diagnostics Lab Review

— Written By

Overall, total turfgrass samples submitted in 2020 to the NC State Turf Diagnostics Lab were lower than samples submitted in 2019, most likely due to an extended closure (52 days) during the beginning of COVID-19 restrictions. As expected, the majority (80%) of our samples came from golf course putting greens. Creeping bentgrass putting green samples were down 27% while bermudagrass putting green samples were only down 3.5% when compared to 2019. Below you will find information regarding all golf course putting green samples submitted in 2020. Enjoy!

Client Distribution chart image

WARNING! – These charts only indicate the samples we have received in our lab here at NC State. The following post focuses mainly on data collected from golf course putting green samples (creeping bentgrass and bermudagrass).

2020 Turfgrass Sample Origin chart image

45% of all turfgrass samples came from North Carolina. 74% of all turfgrass samples came from the SE United States.

2020 Bentgrass /Poa Sample Origin chart image

33% of all creeping bentgrass/Poa putting green samples came from NC. 48% of all creeping bentgrass/Poa putting green samples came from the SE United States.

2020 Bermudagrass Sample Origin chart image

42% of all bermudagrass putting green samples came from NC. 86% of all bermudagrass putting green samples came from the SE United States.

We typically receive samples from cases that are very hard to diagnose in the field alone. Therefore, these charts don’t necessarily represent the major disease outbreaks, but illustrate what causes the most head scratching if you will.

First, let’s take a look at which cultivars and varieties we receive the most. This is NOT an indication of one being more susceptible to disease or problematic than another. This was compiled from all samples submitted in 2020 and would likely match any survey that asks “What do you have planted?”. Remember, we receive most of our samples from the southeastern US with a lot of those coming from right here in North Carolina.

Common Cultivars chart image

Next, let’s take a look at actual disease diagnoses. If you remember from an earlier post, 35-40% of the time we do not find any active disease-causing organisms in samples. This could be due to any number of factors such as it never was a disease, it was a disease and the damage was done too long ago to detect, or it was a disease and you’ve suppressed it with your fungicide program. I’m looking right at you folks who send samples after spraying everything in the barn BEFORE you collect your samples! For simplicity sake, we have combined creeping bentgrass, creeping bentgrass/Poa annua blended, and Poa annua samples together since the diseases are very similar and occur during similar times of year.

Bentgrass/Poa Putting Green Samples chart image

As the industry in our area continues to shift towards ultradwarf bermudagrass putting greens, creeping bentgrass samples continue to decline.

2020 Bentgrass/Poa Putting Green Samples chart image

Bent/Poa samples followed a fairly normal monthly distribution pattern with the majority of samples coming during the summer in June, July, and August. We typically see a sharp drop off in samples around September, however, in the past couple of years, these samples continue to trickle into our lab well into the fall. Record rainfall across much of the state likely contributed in part to lingering issues.

Top 10 2020 Bent/Poa Diagnosis chart image

Now, think about all of the problems listed in the bar graph above. With the exception of summer patch and fairy ring when they create nice little rings, they can all look similar! It’s very hard to diagnose most of these biotic and abiotic diseases in the field with 100% accuracy without looking under a microscope or testing for high salt levels. Also, receiving a diagnosis of “no pathogen found” is equally as valuable as receiving a disease diagnosis. There are lots of things that cause turfgrass quality to decline, don’t assume it has to be a disease. It should be noted that while we do not offer a service for a nematode assay, we do report root-knot and lance nematodes because they are endoparasites (inside the roots) and easy to see/don’t get washed away like ectoparasites (outside the roots).

Chronology chart image

The chart above shows when each disease was diagnosed for bent/Poa putting green samples. The smallest bars usually indicate only a handful of confirmed cases, whereas the larger bars represent many confirmed cases through that time period.

2020 Bent/Poa Diagnosis chart image

New for this year’s report, we have added all of the diagnoses we made throughout the year to illustrate what we see and to include those that don’t make the top 10 list above. There were 18 different diagnoses in 2020 on creeping bent/Poa samples. This does not include a diagnosis of “no disease activity”.

Bermudagrass Putting Green Samples chart image

While this is the inverse of the bent/Poa chart above, this graph shows the rise of bermudagrass putting green samples over the past several years due to the industry shift towards these grasses for putting green surfaces as mentioned previously.

2020 PG Samples chart image

Bermudagrass sample submissions by month follow a very similar path each and every year. The problems are fairly well distributed throughout the year with spikes in the spring and fall as bermudagrass exits and enters dormancy respectively.

Top 10 Bermudagrass Diagnosis chart image

Just like in 2019, take-all root rot (TARR) remains at the top of the list. We saw a significant increase in the occurrence of this disease starting in fall of 2015 when weather conditions were abnormally wet and warm for extended periods of time. Just like bentgrass diseases, a lot of these can look alike and require a microscope to make an accurate diagnosis.It should be noted that while we do not offer a service for a nematode assay, we do report root-knot and lance nematodes because they are endoparasites (inside the roots) and easy to see/don’t get washed away like ectoparasites (outside the roots).

Chronology chart image

The chart above shows when each disease was diagnosed for bermudagrass putting green samples. The smallest bars usually indicate only a handful of confirmed cases, whereas the larger bars represent many confirmed cases through that time period. Just like 2019, we received a lot of mini-ring samples late summer through early fall in 2020 with a lot of those diagnoses being made over email and text messages via photos, which are not counted as physical samples as represented above. We believe mini ring is more severe under low fertility and it’s likely those affected may have lost more fertility than they realized during the extended rainfall periods prior to symptom development.

2020 Bermuda DIagnosis chart image

New for this year’s report, we have added all of the diagnoses we made throughout the year to illustrate what we see and to include those that don’t make the top 10 list above. There were 16 different diagnoses in 2020 on bermudagrass samples. This does not include a diagnosis of “no disease activity”.

Bottom line: As you can clearly see, both bentgrass and bermudagrass continue to have their fair share of disease issues!

If you would like to see this same information from recent years, please click the links below :

2015

2016

2017

2018

2019

Written By

Lee Butler, N.C. Cooperative ExtensionLee ButlerExtension Coordinator Call Lee Email Lee Entomology & Plant Pathology
NC State Extension, NC State University
Updated on Jan 25, 2021
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