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Fall is in the Air

September 20, 2010

A change of seasons is upon us.  The leaves are beginning to drop from some trees and the day lengths are getting noticeably shorter.  September has brought with it cooler day and nighttime temperatures and average 4-inch soil temperatures even dipped into the high 50’s yesterday.  These favorable environmental conditions have allowed existing turf the chance to recover and newly sown seed the opportunity to germinate and begin to cover.

The fall is also a great time to clean up unwanted creeping bentgrass.  Because of all the rainfall and submerged conditions we experienced during the summer months, creeping bentgrass had an opportunity to gain a competitive advantage and may have spread into areas where it wasn’t present before.  Luckily, creeping bentgrass can be controlled with Tenacity herbicide.

Tenacity is a systemic herbicide with pre- and post-emergence activity on many grass and broadleaf weeds.  Tenacity is also capable of selectively removing creeping bentgrass from Kentucky bluegrass, perennial ryegrass, tall and fine fescue.  Multiple applications of Tenacity are required for complete control of creeping bentgrass.  

Tenacity works by inhibiting HPPD enzymes which aid in the synthesis of carotenoids.  Carotenoids help to protect the plant from excess light energy received from the sun.  Without these protective carotenoids, the excess energy causes new growth to turn "bleach" or turn white and eventually kills susceptible plants.

I have done quite a bit of work with Tenacity.  Below are some pictures from my research and from golf courses who have used the product. 

Plot of turf adjacent to a creeping bentgrass putting green after recieveing one application of Tenacity herbicide.  The bentgrass (susceptible) turns white, while the Kentucky bluegrass remains unaffected.
Here, Tenacity was applied to an intermediate cut of Kentucky bluegrass to clean up creeping bentgrass that had invaded from the fairway.  Bleaching of the bentgrass appears after just 1 application.
Applying tenacity next to monostands of creeping bentgrass needs to be done with caution.  Here, spray drift from the adjacent treated turf caused bleaching symptoms on a creeping bentgrass green.  Bentgrass will not be completely controlled after one application but the "bleaching" symptoms can be unsightly in the wrong spot.
Multiple applications of Tenacity are needed for complete control of bentgrass.  Here, three applications have killed the majority of creeping bentgrass in a stand of Kentucky bluegrass. 


For more information about Tenacity herbicide and its various uses visit the Syngenta Tenacity page.


Iowa Turfgrass Field Day Review, Andrew Hoiberg

July 27, 2011

Iowa Turfgrass Field Day has returned! Everyone associated with this event are thrilled to have it back and we know the turf industry is as well. We would like to thank everyone who pitched in to help, all the speakers, the vendors, and most of all, the attendees. Without a great industry like we have in Iowa, none of this would be possible.

Below you will find a recap for the first half of the program and some take home messages from the research and demonstrations that were highlighted at this year’s event. A recap for the second half of the program will follow tomorrow.

NCERA Bentgrass Trial: Dr. Christians showed us the NCR Bentgrass variety trial that aims to maintain bentgrass with limited fungicide inputs and to test different cultivars natural resistance to disease pressure, namely dollar spot and brown patch. The trial has 24 cultivars of commercially available creeping bentgrass. This trial is still underway but there are cultivars that are standing out. “Declaration” is cultivar that others are measured against for natural disease resistance. 

Biostimulant Study: Quincy Law, a recent graduate of the ISU turf program, filled us in on his Ajinomoto study. The objective of this study was to determine the effect of an amino acid based fertilizer upon growth and shoot density of "Penncross" creeping bentgrass. Previous work with an amino acid containing product, GreenNcrease, had resulted in higher shoot densities when applied to mature turf. Treatment applications of three natural products at varying rates, along with urea, were made every two weeks to fairway height turf (0.5 inches). Color, dry clipping weight, dollar spot ratings, total nitrogen analysis of clipping tissue, and shoot densities were all recorded monthly.

Plots receiving applications of GreenNcrease, an Ajinomoto product, had significantly higher shoot densities. GreenNcrease applied as a biostimulant along with a regular fertility regime may increase shoot density. An increased shoot density provides for a more competitive turf stand and better playing surface. The trial completed in 2010 is being repeated on the same plots to investigate the effect of these products when used over time.


Imprelis update: As many of you know, Imprelis herbicide has been in the news a great deal this year as it is suspected of causing damage to White Pine and Norway Spruce trees. It appears as though the herbicide could be moving downward into the soil and being absorbed by mature root systems that extend well beyond the traditional drip line cutoff for spraying. If you have had problems with Imprelis, it is recommended that you contact DuPont. Dr. Christians also spoke about an Imprelis trial examining the efficacy of the herbicide on grassy and broadleaf weeds when applied at various timings in the spring/early summer. The results of this trial will be available this fall. Also, stay tuned for further updates concerning Imprelis as more information becomes available.

Nitrogen based establishment: This trial is attempting use increased rates of nitrogen during establishment of both Kentucky bluegrass and perennial ryegrass hasten the production of aboveground plant mass and improve the wear tolerance during traffic stress. So far, we have been able to detect differences in nitrogen rates as far as fill in and plant maturity, especially when compared to the untreated controls. From what we have seen thus far, it looks like applying 0.25 lbs N/1000 ft2 per week for 8 weeks of establishment for a total of 2 lbs of N produced the most aesthetically pleasing perennial ryegrass with regard to color and density. Incremental increases beyond 0.25 lb N per week caused ryegrass to grow excessively, which could potentially increase mowing requirements.


For Kentucky bluegrass, more nitrogen is necessary to achieve a dense stand that can withstand traffic. We have also had to use 4 applications of Tenacity herbicide at 4 oz/A spread throughout the spring and summer to keep weeds at bay and give the bluegrass a chance to establish enough for cleated traffic. It appears that at least 0.5 lbs N/1000 ft2 per week for 8 weeks during establishment is necessary to achieve maximum density. However, as we continue to collect data on this study, we may find out that rates of 0.75 or even 1.0 lbs N/1000 ft2 per week are best for rapidly establishing bluegrass.

Andrew Hoiberg
Graduate Student
Iowa State University