The efficacy of Tenacity for creeping bentgrass can be improved.
The experimental area was treated with Tenacity.Tenacity treated creeping bentgrass has turned brown.The photo is of Deying Li.
Many studies have been conducted to take advantage of Tenacity, a unique product launched by Syngenta in 2009.It can be used to control creeping bentgrass from other cool-season grasses.
There are different cool-season species of bentgrass that can escape to surrounding areas.Poor playing conditions and bad visual quality are the results.
The efficacy of a foliar systemic herbicide application depends on a number of factors, including reaching the plant leaves, retaining herbicide on the leaf surface, penetration into the leaves and movement to the site of action.Any attempts to improve the efficacy of a foliar systemic herbicide should address one or more of the basic factors.
Tenacity is a systemic pre- and post-emergent weed killer.It works by blocking the HPPD, which is essential for the synthesis of carotenoids.Excess light energy destroys chlorophyll and causes new growth to appear white before it dies (Giese et al., 2005).
The Tenacity label addresses factors of soil hydration, leaf surface retention and penetration, as well as persistence in the plants, in addition to uniform application.
The hypothesis of our current study was led by this.If the sunlight is not intense, the herbicide wouldn't be as effective.Dead leaves of creeping bentgrass caused by an initial Tenacity application may block light penetration to the lower canopy.The removal of dead creeping bentgrass leaves could improve the efficacy of Tenacity.In addition to non-ionic surfactant, could other adjuvants, such as urea ammonium nitrate, improve the herbicide absorption?
In 2007, an experiment was conducted in field plots with an established stand of BrightStar perennial ryegrass overseeded with Penncross creeping bentgrass at the Agricultural Experiment Station, Fargo, N.D.The soil had silt, sand, and 52 percent clay.
The analysis showed the soil's P, K, and pH.The grass was mowed weekly.At 2.0 lbs, nitrogen was applied.per 1,000 sq.In May and September, the urea can be found in two equal applications.It was applied at 3.5 lbs.per 1,000 sq.There are two equal applications in May and September of each year.Irrigation was provided.
There is a treatment list for creeping bentgrass control.
A split-plot design was used to arrange the experiment.The whole plot treatment was Raking.Tenacity was at 0.8 and 1.0 ounces.A.i.On a two week interval, per acre was applied with either 0.25 percent or 2.5 percent UAN solution.
The first treatment in 2008 was applied on July 24.The first application of the sequential treatments was applied at the same time as the single treatment.The herbicide was applied with a backpack sprayer pressurized with carbon dioxide at 36 psi and equipped with flat-fan nozzles at 19 inches spacing held about 18 inches above the soil surface to deliver a spray volume of 10 gal.It is per acre.
The raking treatment was applied using a power rake set that was 1.2 inches high.The clippings were removed using a spring rake.1 to 30 equals slight, 31 to 60 equals moderate, 61 to 99 equals severe injury, and 100 equals no effect at all.On May 29, 2008 and May 14, 2009, the survival of creeping bentgrass was evaluated.
The data was analyzed for creeping bentgrass control.Fisher's protected least significant difference was used to compare treatment means.
Table 2 shows the effects of dead tissue removal by raking on creeping bentgrass control after treatment with Tenacity.
It took three and four weeks after treatment in 2008 for creeping bentgrass control to return to normal after removing clippings and dead leaf tissue.The raking effects on creeping bentgrass appeared in the spring of both years.
The lower average temperature in 2008 might be the reason for the differences between the two years.It shows that temperature and sunlight intensity have an effect on Tenacity.There was low efficacy of Tenacity in controlling creeping bentgrass under low temperature conditions.
Table 3 shows the control of bentgrass at different weeks after treatment.
There are applications of 1.0oz.In 2007, the highest observed creeping bentgrass control was 93 percent, and in 2008, it was 97 percent.When applied at either low or high rates, adding UAN improved Tenacity efficacy.The study showed that, without raking or adding UAN to the spray solution, only 78 percent to 82 percent control was achieved.
Only three sequential applications of 1.0 oz. were compared to other treatments.One year after the field study, control of creeping bentgrass was provided by two-week intervals with both UAN and non-ionic surfactant.
Tenacity at or below an annual total rate of 3 ounces.In one application or in three sequential applications on two-week intervals, moderate creeping bentgrass control is provided under the climate and soil conditions at our experimental site.The control of creeping bentgrass with removal of dead clippings and adding UAN to non-ionic surfactant and Tenacity was satisfactory.It is per acre.Since little dead leaf tissue will be removed by mowing following an application of Tenacity, it may be necessary to remove dead leaves by raking prior to the next treatment in order to improve efficacy.
Tenacity should be applied at 1.0oz.Each of the three sequential applications uses a non-ionic surfactant plus UAN with power raking.The greatest control of creeping bentgrass can be achieved with power raking.
Deying Li is an associate professor in the Department of Plant Sciences at North Dakota State University.He can be reached at deying.li.
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