Is it Starting to Feel Like Groundhog Day?

So I bet many of you in the south are feeling like Bill Murray in the 1993 movie “Groundhog Day”. I know I am. Everyday we look at turfgrass samples with the same problem. Heat-related stress and decline and severe nematode populations! Many superintendents that I have spoken to are getting as frustrated as me. This heat is getting old. We are now sitting at 45 days above 100F here in Stillwater. In the Oklahoma City area they are knocking on the all-time record of 50 days! Everyday the same thing…

The OSU Turfgrass Diagnostic Laboratory has churned through a bunch of creeping bentgrass putting green samples in the last couple of weeks. The large bulk of samples have extremely short root systems. The heat has really taken its toll on creeping bentgrass in much of the south central U.S. Throw in some nematodes damaging what roots are left and we have a lot of turfgrass in serious decline. Very high populations of stunt (Tylenchorhynchus spp.) and ring (Criconemella ornata) nematodes have been observed in many of the samples submitted. We have seen populations of stunt nematodes as high as 4,000 individuals in 100 cc of soil. This is about 26 times the threshold we consider the “danger zone” on creeping bentgrass. Ring nematode populations have been coming in as high as 2,000 individuals per 100 cc soil, which is about four times the “danger zone” population level. So as you can see, things are getting tough here at the end of the summer in the south. Many are praying for cooler weather and rain. Although, those that have gotten rain have been struggling with wet greens and hot weather, which makes for a whole different set of hurdles.

Other issues in the diagnostic lab have been few and far between, but we did have one sample with Pythium root rot. This was an odd situation where the greens got dry and severe wilt began. To compensate the newly hired assistant superintendent turned the irrigation system on and severely over-irrigated multiple times. When you have lots of soil moisture and high temperatures in the rooting zone, Pythium root rot can help finish off the already declining plants. So while, not the initial cause of the problem, we did identify something other than nematodes. In our research plots, brown patch has also been active and dollar spot comes and goes pretty much as the humid weather comes and goes.

The long-term forecast is showing cooler temperatures, if we can just get through this weekend. As Dr. Kaminski has said in a previous post “there is light at the end of the tunnel.” So keep your head up and your fingers crossed for cooler temperatures, I think we will be there soon!

More on Nematodes in The Southern U.S.

The heat is still cooking us here in Oklahoma and the rest of the south-central U.S. We also have been receiving many samples in the OSU Turfgrass Diagnostic Laboratory. Most of the samples are suffering from severe heat-related stress. This past weekend has been one of the hottest we have seen yet here in Stillwater. According to the Oklahoma Mesonet station summary for Stillwater, we topped out at 105 F on Saturday and 107 F on Sunday. As I said in my previous post, if you are experiencing these temperatures and still mowing everyday at ultra-low heights, making cleanup passes on edges of greens, have your grooved rollers on, and are doing anything else that causes unneeded stress on turf plants, STOP! These practices will facilitate a quick decline of putting greens under these sustained high temperatures and there is nothing you can do to facilitate recovery until cooler temperatures (high temperatures less than 85 F) prevail.

In addition to samples that are under severe heat stress, we have been receiving many samples with high nematode populations. I talked about this in another post and Dr. Tomaso-Peterson also wrote a great synopsis on nematodes. We have been receiving some questions on how nematodes cause damage to plants so I’ll attempt to explain a bit using creeping bentgrass as the host of interest.

Nematodes cause damage on creeping bentgrass by feeding on the roots. Feeding by these tiny animals (roundworms) can injure and impair root functions such as water and nutrient uptake. Nematodes may feed externally or internally. Utilizing a specialized spear-like feeding structure (stylet), nematodes puncture plant cells in the roots, causing discolored areas (lesions) or swellings. Nematode activity also can predispose the grass to attack by other pathogens such as fungi and can cause the plants to be more prone to heat-related stress. Some of the most common plant pathogenic nematodes we find in putting greens in the southern U.S. include lance (Hoplolaimus spp.), ring (Cricinemella sp.), spiral (Helicotylenchus sp.), stunt (Tylenchorhynchus spp.), sting (Belonolaimus spp.), sheath (Hemicycliophora spp.), and root knot (Meloidogyne spp.). Female nematodes can lay many eggs (up to 500 eggs), which in turn hatch into juveniles. These juveniles will then mature through a series of four molts then becoming adults. Nematodes are motile in the soil for very short distances. Long distance spread occurs through surface water runoff and movement of infested soil from location to location. In non-tilled soil environments such as on a golf course, movement of infested sod is a primary method of dispersal. Generally speaking, sandy soils are more likely to have nematode problems than soils with a high clay content. Therefore, sand-based putting greens are a great environment for nematodes to flourish.

Above ground symptoms of nematode induced diseases will often resemble drought stress, general lack of vigor and little to no response to irrigation, fertilization or even fungicide applications. Symptom expression is directly related to the number of feeding nematodes. Nematode populations can increase very quickly in the summer months. The length of the nematode life cycle is partially regulated by temperature. As temperature increases, life cycles get shorter and the population of nematodes can increases at a faster rate. In addition, if we consider creeping bentgrass plants, as the heat increases, root and shoot growth can slow or stop. If roots have stopped growing (and maybe dying) due to high temperatures and there is a lot of nematode feeding, it is easy to see how creeping bentgrass plants can die very quickly without much warning. Further complicating matters, is the presence of multiple groups (genera) of plant pathogenic nematodes, which can have a synergistic effect on disease severity and symptom expression. The best way to confirm a nematode problem on a stand of creeping bentgrass is to have a soil sample evaluated. These assays are usually expressed in numbers of individuals of different nematode genera per volume of soil. Various treatment threshold numbers have been established for some nematode genera on certain turfgrass types.

Management options:
Few chemical fumigants/nematicides exist as options for controlling plant pathogenic nematodes. Therefore, superintendents should practice methods to promote a vigorous root system on creeping bentgrass plants in the spring before stressful growing conditions prevail in the summer months. I have written before about managing nematode-induced stress. However I will reiterate here. Cultural management should include raising mowing heights (.160 in. or more would be advised), adjustment of the frequency of mowing and rolling to reduce the amount of stress applied to the turf stand, and continued frequent, light applications of fertilizer and water are recommended. Any practice that reduces stress and damage to turf plants will assist the plants in surviving the additional damage that nematode feeding causes. Regular soil assays should be done if nematode activity is suspected.

Dr. Nathan Walker and myself have various experimental chemical treatments that we are evaluating for efficacy toward nematodes. In future posts I hope to comment and show some data. Hopefully we will have something positive to present. Until next time…

Dead Bentgrass Makes Headlines

Well, you know things are rough when the local media is writing about Pythium, aerification, and MiniVerde bermudagrass. Unfortunately that's where we are here in North Carolina and many other parts of the southeast. Check out the following article from last Thursday's Charlotte Observer: 


Hot Weather Turning Putting Greens to Toast


Overall, I think its a pretty accurate description of the struggles that golf courses are facing in the region. I'd be curious to hear everyone's thoughts. There are also a couple of factual errors in the article. I'll give a prize to the first people to point them out by leaving a comment on this post!


A lot of people have been asking about converting their greens to ultradwarf bermudagrasses. They are definitely a good option in certain situations, and several courses in the area have made the switch with great success.


My only advice is this: if you can't maintain good bentgrass greens because of problems with shade, air movement, or soil drainage, then you won't be able to maintain good bermudagrass greens either. The courses that have been most successful in converting to ultradwarfs also removed trees, improved air movement, and corrected drainage problems. Who knows, maybe bentgrass would be doing just fine with these improved growing conditions?

Heat + Rain = Dead Grass

First, let me welcome Lane back;

I hope your sabbatical was productive and recharged your batteries! Second, I would also suggest a corollary to the equation, No Wind + Heat = Dead Grass, and that is: Heat + Rain = Dead Grass.

Another area where stress begins to rear its ugly head is in the area of water management- too much, and not enough.

All too often, we see situations where relative humidity is high, and "hand watering" is done to "cool the plants off". Unfortunately, when RH is high, very little of the water

you put down will evaporate, and this creates the potential for several bad things to happen. As Lane described in his post, fans are incredibly important especially in the Southeast because of the need to reduce the local relative humidity so that the plants can manage the heat.

Fungicide programs are also showing excellent differences, and you can tell the difference between those that perform and those that miss a key disease this year.

To give you an idea of just how we are doing this year, a superintendent in TN sent the following out to his colleagues, and I thought it was interesting:

"Over the weekend I had some fun with numbers. I pulled all my weather records for my course for the past 17 years. I counted the number of 90 degree or above days in the months of June , July and August. Pretty interesting. In 2004 we only had 5 days at or above 90 the whole year. 2006, 2007 we had 40 and 47 days respectively. The highest we had ever had in June was 13 in 1996. The highest ever in July was 28 in 1993. The highest ever in August was 29 in 2007.
1993 must have been a rough year because we has 54 days total, but we were closed, rebuilding our greens that year so it didn't hurt me any.

On average we have had 6.8 days in June at or above 90, 11 days in July and 11.5 days in August.

This year we had 18 days at or above 90 in June and we have already had 18 days in July with a week to go.

The numbers are probably a little different in other areas, but by my measure, that had to be the most stressful June for at least the last 17 years and with the exception of 1993, it looks to be the most stressful July. By far the most stressful two month stretch during that time.

Pass this along to others if you think it will make them feel better. Or just remind them that we are all in the same boat, and that football season is getting closer every day."

It seems to me that golf provides an adequate analogy for taking care of turf under this kind of stress. We have all heard some version of the saying, "The person that misses it the best will win", and I think an appropriate version of that for a summer like this is, "The superintendent who knows how to lose a little turf will carry the day". Like he said, "football season is getting closer every day". Try to stay cool everyone!