Magazine - Professional Turf Diaries With Jerry. Pt. 8

By Jerry Spencer in Consultancy on 27th Apr 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 option.

Cool-season grasses.
In most instances, Poa annua control was acceptable using selective rates, dates, and frequency of application in perennial ryegrass, Kentucky bluegrass, and creeping bentgrass maintained as fairways. There were a couple of references showing that N and Fe applied with ethofumesate improved turfgrass safety.

Couch greens, tees, and fairways overseeded with perennial ryegrass.
Golf course superintendents that manage couch greens has a continued Poa annua problem trying to control the weed during the autumn, winter, and early spring. They generally have four choices that can be used:

1- Apply a PRE herbicide 45 to 60 days prior to overseeding. This practice will normally result in poor Poa annua control by mid to late winter. The poor control occurred from the dissipation of the PRE herbicide by the time of overseeding with perennial ryegrass, thus poor weed control will follow.

2- Apply pronamide about 2 weeks before overseeding to control the emerged Poa annua and follow by activated charcoal 2 to 3 days prior to overseeding. The pronamide will control the emerged Poa annua, but has little effects on the weed after the charcoal has been applied.

3- Apply ethofumesate at 4 and 8 weeks after couch is overseeded with perennial ryegrass (greens not recommended). Ethofumesate should be applied only after couch is dormant and do not apply within 3 months of green-up in the spring. Therefore, ethofumesate treatments will have some limitation as to where it can be used.

Ethofumesate can cause perennial ryegrass discoloration through most of the autumn but will usually recover fully by January or early February. There has been no research conducted using N and Fe with ethofumesate on overseeding perennial ryegrass. These treatments could also reduce the discoloration or shorten the recovery period as reported on cool-season grasses in the northern region.

The graph below shows comparative temperatures for Australia vs USA and where previously mentioned trial work was carried out. For example…’ In North Carolina ethofumesate applied in October controlled a higher percentage of Poa annua than when the same rate was applied in August, September, or December’.…In October the average temperature is 21ºC. This equates to September in Sydney etc. The graph below can be used to cross reference relative temperature data between countries.

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