3 mistakes to learn from when applying products to turf

By |  October 22, 2014 0 Comments

During a recent field day I asked, “How many people here have ever killed grass because of a product they applied or a mistake they made?” Naturally, few raised their hand out of fear of embarrassment. I then told the crowd, “if you did not raise your hand, you were lying.”

This may be an overstatement, but many of us have killed grass, or at least severely injured grass because of a mistake we made. There are many decisions to be made as a superintendent and some of them revolve around the products used to maintain the health of the turf. With these decisions comes the possibility of making mistakes.

One of my biggest mistakes was not understanding a herbicide well enough and the next thing I knew I was reseeding two acres of Kentucky bluegrass. Note to self: sethoxydim kills Kentucky bluegrass. On the positive side, the more grass I killed through a management mistake, the more I learned about managing turf.

Because I have made several product-related mistakes, this got me thinking that it would be informative to put together a demonstration that would revolve around potential mistakes turfgrass managers have made, almost made or contemplated, “what would happen if I did this?” Unfortunately in the turfgrass industry, a mistake can cost an individual his or her job. Looking at a few examples of mistakes allows discussion of possible outcomes, remedies and things that could have been done to mitigate the problem.

Mistakes with products can happen for a number of reasons and include: not understanding the product you are using; reading the label incorrectly, including potential problems such as compatibility, retreatment intervals, application rates, etc.; incorrect calculations, including putting the decimal point in the wrong place; improper equipment calibration; thinking more will be better; applying a second product to try to remedy the initial mistake, causing an additional mistake; improper storage of products (i.e. freezing or heat).

I want to highlight three mistakes from the 19 different demonstration treatments conducted. These include issues that may arise from plant growth regulators (PGRs), foliar fertilizers applied at too high of a rate and a common golfer mistake leading to consequences none of us like. All “mistakes” were applied to a V-8 creeping bentgrass (Agrostis stolonifera L.) putting green mowed at 0.125 inches six days a week.

Mistake #1

Two of the most commonly used PGRs are trinexapac-ethyl and paclobutrazol. Both are labeled for greens, tees and fairways. What I found interesting with the trinexapac-ethyl label is the fact that the “Golf Course Greens” rate is right beside the “Edging/Banding” rate. Now I know we all read the label from cover to cover, multiple times, and are never in a hurry, but this got me thinking that someone could easily mistake the “Golf Course Greens” rate for the “Edging/Banding” rate. If this happened, you would be applying 7.33 times the greens label rate. So naturally, I thought it would be informative to apply trinexapac-ethyl at 44 oz./acre instead of the creeping bentgrass greens label rate of 6 oz./acre.

I was fairly surprised that the turf did not show more yellowing than it did two weeks after application (Photo 1). The plot looked just fine, but it was not growing at all. This lack of growth would most certainly be a problem in a real world golf situation with the amount of traffic received, but few issues were seen on the research green. Ball marks would not heal as quickly, turf from old hole locations would not blend together as quickly, and the continued traffic from mowers and golfers would certainly stress the turf.

Paclobutrazol is another PGR that is often used on putting greens. The mistake that could happen with this product would be using the fairway rate instead of the greens rate. The low greens rate is 6.4 oz./acre and the high fairway rate is 32.0 oz./acre.

The plot treated with paclobutrazol at two weeks after application was much like the trinexapac-ethyl plot, with very little discoloration, but also very little growth (Photo 2). Keep in mind that this area was 100 percent creeping bentgrass. If the plot would have had any Poa annua in it, it would have looked much worse.

I picked these two PGRs as a “mistake” because I hear at least one time per year of an excessive rate of a PGR being applied to a putting green. When we make mistakes we immediately want to find a way to rectify the situation. There is an urge to be proactive and find a solution to maintain turfgrass health.

The two PGRs above provided an interesting opportunity to do just that. Trinexapac-ethyl and paclobutrazol are both gibberellic acid synthesis inhibitors. So, if the product I just applied is preventing the plant from synthesizing gibberellic acid, why don’t I just give it some gibberellic acid? Seems logical, right?

Gibberellic acid is associated with several plant processes, but it is most involved with cell elongation and cell division. If I have applied a product that inhibits the synthesis of gibberellic acid, then applying gibberellic acid to the plant will surely solve my problem.

There is one such product available that will provide the gibberellic kick that I’m looking for. I applied the gibberellic acid product at 12.0 oz./acre on the same plots that received high rates of trinexapac-ethyl and paclobutrazol at three and seven days after PGR application.

When gibberellic acid was applied at three days after PGR application, there was a very quick response. Within 24 hours there was noticeable growth within the plot area. Great news, right? Along with this growth there was significant yellowing. This may be attributed to the plant growing much faster than the plant wants to grow, resulting in spindly growth and subsequent yellowing (Photos 3 and 4).

Turf response to the gibberellic acid application seven days after the PGR application was initially a little different from the turf response to gibberellic acid applied three days after the PGR application. For the first four days after the gibberellic acid application was made (seven days after the PGR application), I did see a rebound in growth, but no yellowing. I thought I was on to something. However, on day five, the plot areas began to yellow and went down the same path as gibberellic acid applied to the plots three days after application — spindly, yellow growth (Photos 3 and 4).

As a check, I also applied gibberellic acid alone, which resulted in almost immediate increase in growth with yellowing and eventually the plot area turning a slight orange color (Photo 5). There was never much scalping of the gibberellic acid treated plots, but the cut was not very good with the rapid and spindly growth of the plant (Photo 6).

What I have concluded from this is that being proactive and looking for a quick fix of my mistake resulted in a much worse situation. Also keep in mind that the gibberellic acid product used is only labeled for bermudagrass greens, thus I had to guess what rate would be best for creeping bentgrass. I was getting very little growth from the plot areas receiving high rates of PGR, it did not kill or even turn these areas yellow. Letting the plant metabolize the PGR would have been the best decision in this situation. Sometimes doing nothing is the best option.

Mistake #2

Ammonium sulfate is commonly used on creeping bentgrass putting greens, applied both as a granular and as a liquid. Ammonium sulfate provides a quick response, even in cooler temperatures, and is often used to acidify the soil. However, ammonium sulfate has a high burn potential, making it difficult to use in some situations, especially during summer.

I decided to look at two rates of ammonium sulfate, 0.50 pounds N/1000 ft2 and 1.0 pounds N/1000 ft2 applied as a liquid and not watered in. Most liquid applications of ammonium sulfate to creeping bentgrass putting greens would not exceed 0.20 pounds N/1000 ft2. Both rates of ammonium sulfate quickly burned creeping bentgrass. Within 24 hours, there was moderate tip burn and within 48 hours there was severe tip burn at both treatment rates (Photos 8 and 9).

This would cause many turfgrass managers to quickly panic. However, 72 hours after application some of the tip burn was mowed off, especially from turf fertilized with 0.50 pounds N/1000 ft2 rate (Photo 10). Six days after application both treated areas looked great (Photo 11). The initial burn quickly grew out and was mowed off. This is another case of letting time solve the mistake. Using iron or a pigment to mask the burn would have been unnecessary as the turf quickly bounced back.

Mistake #3: A golfer issue

If you have ever worked at a golf course you understand the issues that occur with bug repellant spray. Although this is a mistake many of us have had to deal with, it is not a mistake that most of us would make. However, it is still informative to look at a few photos.

The solvents in bug spray provide an effective and quick kill of creeping bentgrass. Many of us have seen the footprints left behind by a golfer spraying their legs while waiting on the tee. Bug spray thoroughly killed this plot area (Photo 12) within 12 hours of application.

What I found interesting though, was how the bug spray continued to kill the area that originally was not sprayed (Photo 13). At this point, education and signage indicating the issues that can arise from inadvertent bug spray applied to creeping bentgrass is the best route to take.

Managing the mistakes

There are many mistakes that can be made as a turfgrass manager and many of them revolve around the products we use. I suggest doing several things to prevent mistakes.

Check and double-check all product labels and application rates. Understand the products you are using and how they affect the plant to which they are applied. Make sure your equipment is calibrated correctly. Read, read and re-read the label. Make sure you are using the appropriate rate and volume necessary for the product. There is also valuable information on tank mixing issues, including dos and don’ts on many product labels. Have a second person verify the products that will be used.

If a mistake does happen, communicate with your superiors, staff and parties of interest as soon as possible. This will allow you to control the information and reduce the amount of misinformation if someone finds out about an issue secondhand. Seek help and advice. Talk with peers, extension specialists, vendor reps and anyone you think can help. Get as many people as you can to understand the situation. They may provide a solution or at least a timeline of how long the problem will persist.

Be patient. Although we all want to be proactive, there are some situations where the grass just needs time to recover and there is not much we can do to hasten the recovery time. It is hard to do, but sometimes doing nothing is the best approach.

The turfgrass industry is a great profession, but it can be volatile, especially if mistakes happen. Good luck and make sure the decimal point is in the right place.

Click on the images below to enlarge them.


This is posted in Research

About the Author: Matt Cavanaugh

Matt Cavanaugh is a research scientist at the University of Minnesota where he collaborates with fellow turfgrass scientists on a wide range of turfgrass research projects. Cavanaugh can be reached at mattc@umn.edu for more information.

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