Magazine - Professional Turf Diaries With Jerry. Pt. 6

By Jerry Spencer in Consultancy on 4th Apr 2008 7:00

In Jerry's diaries we will look at ethofumesate. Ethofumesate has been available for years but is seldom used as other ‘easier’ options are now available which are not always the best option.


Couch suppression.
Couch is extensively used throughout Australia for many turf areas, including sports ovals, golf courses, parks, and other turf areas. However, when it is mixed with other grasses and not wanted in this mixture, it becomes a severe weed problem. Couch contamination with other grasses that has a different leaf texture and growth habit will result in a poor quality turf.

Couch suppression in tall fescue.
Couch is a severe weed problem when mixed with tall in a turfgrass area. A mixture of the two grasses will results in a poor quality turf, due to different leaf texture and growth habit. Tall fescue will have a medium to course leaf texture compared to a finer leaf texture for couch. Since couch goes dormant after the first frost in the autumn, the turf area will be partial green in the winter from tall fescue and partial brown from dormant couch.
In Georgia 3 to 4 monthly spring/summer applications of either fenoxaprop plus ethofumesate (0.35 + 2.24 kg/Ha) or triclopyr plus ethofumesate (1.0 + 2.24 kg/Ha) effectively suppressed common couch throughout the season. Herbicides applied at 4 week interval injured tall fescue more than treatments were made at 6 week intervals. However, turf injury was temporary and tall fescue completely recovered. In a second study conducted in Georgia common couch was controlled > 96% by late summer when growing in a mixed tall fescue turf when treated with fenoxaprop plus ethofumesate at 0.2 + 1.9 kg/Ha. The control was obtained when the first application was made in April and repeated at 3 to 4 weeks for a total of four treatments in one year and five treatments the second year. In most instances, tall fescue was injured slight to moderate for 1 to 2 weeks but fully recovered. Tifway couch was not controlled from fenoxaprop plus ethofumesate treatments at either location in Georgia.

Summary.
Common couch was effectively suppressed in autumn fescue when treated with 3 to 5 applications of fenoxaprop plus ethofumesate. Higher rate required fewer herbicide applications.

Couch suppression in creeping bentgrass green.
Encroachment of couch into creeping bentgrass greens can be a major problem in the where both grasses are grown. This occurs because creeping bentgrass is not adapted to the hot, humid climate as is couch. Therefore, bentgrass in a golf green cannot compete with couch growing in collars and aprons around the green and encroachment will usually occur. Since the mixture of the two grasses results in a poor-quality putting surface, it is desirable to prevent encroachment of couch with chemicals without injuring bentgrass.
Studies on suppressing couch in creeping bentgrass were conducted over a 5-year period in Georgia. During this period ethofumesate and ethofumesate plus flurprimidol were applied with other herbicides at various dates and frequency of applications needed to suppress couch growing in creeping bentgrass green. Ethofumesate applied alone at 1.9kg/Ha in April suppressed couch very little. However, sequential application of ethofumesate plus flurprimidol at 1.68 + 0.85 kg/Ha in April suppressed > 70% couch for 4 to 6 weeks. There was no advantage in couch suppression when treatments were applied in September and April compared to April alone. However, creeping bentgrass was moderately injured (< 30%) for 3 to 4 weeks after treatment in April, but severely injured (< 44%) when applied in September.

Summary.
The suppression of couch growing in a creeping bentgrass green was effective when treated with ethofumesate plus flurprimidol. However, it was necessary to follow the initial full (1.68 + 0.85 kg/Ha) rate in mid-March or early April with four one-quarter rates. It was also important to follow the initial treatment with timely repeated treatments. The second application must be applied at 6 weeks after the initial full rate followed by 3 week intervals for remaining applications. Creeping bentgrass was moderately injured for 3 to 4 weeks following the full herbicide treatment, but bentgrass tolerated the one-quarter rates.

Seedhead suppression with ethofumesate.
Ethofumesate suppressed Poa annua 74% when applied alone at 0.85 kg/Ha, compared to 92% seedhead suppression when a fertilizer with N was applied with the herbicide at the same rate. The higher seedhead suppression was related to the higher Poa annua control obtain from the sequential treatments.

Management practices with ethofumesate.
When ethofumesate or any herbicide is used for Poa annua control, it is important to include optimum management practices that will favor maximum benefit from herbicide treatment.

Rates of ethofumesate.
Most turfgrass weed researchers have indicated that the optimum rates for Poa annua control are 0.85 kg/Ha applied in each of three applications and 1.12 kg/Ha applied in each of two applications. These results occurred in Alabama, Georgia, North Carolina, Virginia, and Maryland. For turfgrass safety with ethofumesate, perennial ryegrass can be treated with a maximum rate of 2.24 kg/Ha per application while more susceptible grasses such as creeping bentgrass and Kentucky bluegrass should be treated with a maximum rate of 0.85 kg/Ha per application. The first ethofumesate application is less important in controlling Poa annua than the second or third application. This is due to the first ethofumesate treatment setting up the Poa annua plant for injury from subsequent applications.

Intervals between ethofumesate treatments.
One week between ethofumesate treatments is not affective in controlling Poa annua. Ethofumesate applied 20 to 30 days apart results in the best Poa annua. Control. Rthofumesate applied at 1.12 kg/Ha controlled Poa annua better when the herbicide was applied in a second application at 30 day interval than at 60 day internal.

Dates of ethofumesate treatments.
In Georgia the optimum treatment date was related to the rate of ethofumesate application . When the herbicide was applied in October and November, Poa annua control was effective from 1.12 kg/Ha rate applied at each application. However, when treatments were delayed until November and December a 1.9 kg/Ha rate was required at each application date for similar control. Other researchers found that rate of ethofumesate determined when treatments should be applied. A 0.56 kg/Ha rate needed four autumn applications while a 0.85 kg/Ha rate needed only 2 or 3 autumn applications. The data from these studies indicated that the November treatment date was better than September. When a single ethofumesate application was made in North Carolina, the highest Poa annua control was obtained in October and followed by November. While the August, September, and December treatments dates resulted in poorest control. When single treatments were made in Michigan Poa annua control was the highest the following late-May when treatments were made mid-August than when applied 2 and 4 weeks later.

Summary management practices with ethofumesate.
Ethofumesate applied for Poa annua control was generally the highest when applied at 1.12 kg/Ha in each of two applications at 30 day internals.

Ethofumesate treatments on creeping bentgrass root growth.
Ethofumesate applied in the autumn in Georgia, did not reduce root growth of creeping bentgrass in December, but the growth in June was reduced by 5% in plots treated at 1.12 kg/Ha and 21% when treated at 2.24 kg/Ha compared to untreated bentgrass. In Australia , creeping bentgrass root length and root health was not affected when treated with ethofumesate alone, ethofumesate plus oxadiazon, or ethofumesate plus bensulide when compared with untreated check. However, new root initiation was less in plots treated with ethofumesate plus bensulide than with ethofumesate alone and ethofumesate plus oxadiazon.

Summary.
The root growth of creeping bentgrass was generally not affected with ethofumesate when applied at < 1.12 kg/Ha.

Ethofumesate treatments on creeping bentgrass drought stress.
Creeping bentgrass in Australia was not affected by drought stress when treated with ethofumesate alone or ethofumesate plus oxadiazon when compared with untreated turfgrass. However, turfgrass treated with ethofumesate plus bensulide had a significantly higher drought stress than ethofumesate alone and combinations of ethofumesate plus oxadiazon.

Summary.
It was observed at a single location that ethofumesate did not affect drought stress of creeping bentgrass.

Turfgrass renovation with ethofumesate.
Renovation of a turf area can mean several things. In this survey it will be referred to as changing a undesirable mixed turf of Poa annua and cool-season to a desirable cool-season turf with the use of ethofumesate. This program is limited to Kentucky bluegrass, perennial ryegrass, and creeping bentgrass.


Converting mostly Poa annua to a desirable turf.
Two different renovation programs were presented in Michigan to convert a poor quality turf into a higher quality turf.

First program.
If the desirable turf species is less than 75% in the turf area, it is best to gradually reduce Poa annua population while increasing the turfgrass. If have 40 to 50% Poa annua, ethofumesate will control the weed and will leave the turf area in poor conditions with lots of bare ground. Plant growth regulators such as paclobutrazol should be used to increase the turf population up to 75%. This process may require as much as 3 years. When the turf reaches the 75% level, start with ethofumesate treatments to control the remaining Poa annua and improve the turf coverage.

Second program.
 A mixed turf of 95% Poa annua and 5% Kentucky bluegrass can be treated in the autumn with ethofumesate at low rates (0.85 kg per ha) in September and October. The 0.85 kg/Ha rate seem to weaken the Poa annua allowing a shift during the winter and early spring from the original 5% to 47% population by spring the first year. It is important not to apply ethofumesate above 0.85 kg/Ha because of outright kill. Ethofumesate must be repeated each year until the desired turf level is reached and then repeated to maintain Poa annua control.
The optimum ethofumesate rate was found to be 0.85 kg/Ha for Poa annua in a turf area to be renovated. The suggestion is that ethofumesate treatment be delayed for 6 weeks following emergence of creeping bentgrass and 8 weeks following emergence of Kentucky bluegrass.

Converting perennial ryegrass to creeping bentgrass.
The treatments used depended on amount of Poa annua.

Program to use when Poa annua population mostly > 80% .

First year.
Seed ryegrass in the autumn followed by multiple ethofumesate treatments to reduce Poa annua population to at least 50% the following spring without losing grass coverage.

Second year. Seed creeping bentgrass in the autumn followed by lower ethofumesate rates to control Poa annua, but not injure the creeping bentgrass.
Third year. Reduce mowing height and continue overseeding with creeping bentgrass and ethofumesate treatments.

Program to use when Poa annua population 50 to 60%.

First year.
Seed both creeping bentgrass and perennial ryegrass in the autumn followed by two ethofumesate rates.

Second year.
Reduce mowing height to 12mm. Seed with creeping bentgrass in late summer and follow with two ethofumesate treatments.
Third year. To complete the conversion to bentgrass, overseeding and ethofumesate should be continued. A complete conversion should be made in 3 years.

Converting a poor quality turf to perennial ryegrass.
The existing turf can be killed with glyphosate, re-established with perennial ryegrass, and treated with ethofumesate to keep Poa annua from becoming re-established.

Summary conversions/renovations.
A poor quality Poa annua turf or a mixed Poa annua with a desired cool-season turfgrass can be renovated into a higher quality turf. A turfgrass manage can select from several programs. However, regardless of program, the conversion or renovation may require several years. The renovation of the old turf can be converted into either perennial ryegrass, Kentucky bluegrass, or creeping bentgrass. Warm-season turfgrass can not be renovated using these programs.

Read more articles in Consultancy, by Jerry Spencer or from April 2008.