Magazine - Professional Turf Diaries With Jerry. Pt. 1

By Jerry Spencer in Consultancy on 7th Feb 2008 6:00

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 options.


USE OF ETHOFUMESATE ON TURF

Poa annua can be one of the most serious weed problems in highly maintained turfgrass. Ethofumesate has been used to control Poa annua; however, the results have been erratic, and ethofumesate is not widely utilized for Poa annua control in turfgrass. In Australia this product is only available as a 500g/L emulsifiable concentrate. It gives effective pre- and early postemergent control of Poa annua in new seedings of perennial ryegrass. However caution should be taken when using this:
· It inhibits the germination of most desirable cool-season grasses other than perennial ryegrass.
· Highly toxic to seedling fine fescues.
· Surface organic matter decreases ethofumesate’s effectiveness. Remove thatch and other debris before applying ethofumesate.
· Not recommended for turf with more than 70% Poa annua.
· Do not use during periods of extreme environmental stress (e.g., heat, cold, drought).
· When used at high rates, Kentucky bluegrass and bentgrass turf may be discolored temporarily.

Ethofumesate Mode of Action
Chemical name for ethofumesate is: (+)-2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranylmethanesulfonate. Trade name for ethofumesate is: Prograss

Herbicidal Use:
Ethofumesate can be applied as preemergence and postemergence to selected turfgrasses for control of weeds. Although ethofumesate has activity on several weed species, it is predominately used for Poa annua control in cool-season grasses. In recent years, ethofumesate has shown activity in suppressing couch when mixed with selected cool and warm-season turfgrasses.

Behaviour in Plants:
Ethofumesate is readily absorbed by emerging shoots and roots, and translocated readily to the foliage. Postemergence applied ethofumesate is poorly absorbed by maturing leaves with a well developed cuticle.
Research conducted in Tennessee indicated that creeping Penncross bentgrass treated with ethofumesate caused abnormalities in root tips. When this occurred, it caused an overall weakening and thinness of root cells and making it easier for the cells to shatter. Other observed injury to bentgrass roots were a slight disruption in organization of cortical roots, enlargement of the cortical cells, and sparse occurrence of root hairs.
The injury to creeping bentgrass treated with ethofumesate was observed by light green leaves, sparse shoot growth, and reduction in root mass growth.

Behaviour in Soil:
Persistence in the soil reported by Weed Science Society of America that the half-life of ethofumesate ranged from > 14 weeks under dry, cold conditions to < 5 weeks under warm, moist conditions. Researchers in UK reported that ethofumesate applied in October (autumn) to a newly planted perennial ryegrass had a half-life just over 8 weeks. However, the herbicide persistence in the soil after 28 weeks was sufficient to reduce Poa annua population by 50%.

Transformation:
Negligible loses and microbially degraded in soil.
Volatilization: Negligible losses.

Mobility:
Little leaching in the soils with >1% organic matter content. Ethofumesate is not readily leached below 15 cm. Researchers in UK reported that ethofumesate was confined to the upper 2 cm of soil profile after 15 months.

Research review
The objective of this research was to characterize the response of Kentucky bluegrasses and creeping bentgrass to a range of ethofumesate rates. Single applications of ethofumesate from 3.4 to 20.2 kg ai/ha (6.8 to 40L/Ha) were made to all four species during May of 1999 to 2001. All four species were injured from rates of 6.7 kg/Ha (17.6L/Ha). Poa annua showed almost no control, with rates 10.2 kg/Ha (20L/Ha), and the highest rate tested, 20.2 kg/Ha (40L/Ha), controlled only 47 to 62% of the Poa annua. Kentucky bluegrass was the least sensitive bluegrass species, with a maximum control of 3 to 15% from 20.2 kg/Ha (40L/Ha) of ethofumesate. Creeping bentgrass was the least sensitive of the species tested, with low levels of control regardless of rate. During 3 yr of testing, maximum control of bentgrass from any rate was 4%. Sixteen Kentucky bluegrass cultivars used for low-cut athletic fields were evaluated for their tolerance to sequential ethofumesate applications during 1999 and 2002. The cultivars showed significant differences in ethofumesate tolerance, with ‘Moonlight’ and ‘America’ never showing any injury to sequential ethofumesate applications, while ‘Northstar’ and ‘Total Eclipse’ were severely injured.

Article supplied by E.T.P - www.etpturf.com.au

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