Carpet grass control - Monument does work - maybe

Monument herbicide has been used - probably for the first time in the NT - as a control option for sedges, carpet grass and annual grasses - on the main oval of a private school, and it has been very successful, so far.

Conditions for spraying were excellent, about 48 hours after mowing, with good soil moisture, and about 48 hours between spraying and first rain. The Monument was followed up by a DSMA spray in about 12 days. After three weeks carpet grass control was over 85%, although some was suppressed rather than killed outright. What remained was a few plants in formerly large patches, suitable for spot spraying or sprayed with a overall spray of further DSMA in a few weeks. Almost all sedges, annual grasses and many other perennial grasses including Chrysopogon acidulatus have been mostly eliminated. A follow up is often used, but may not be needed.

Because of the regular emergence of Mullumbimby couch, almost all year round, periodic use of DSMA will be needed to continue to reduce infestations to a lowered level, and so this will also continue to provide a good option to further reduce the carpet grass "spots" remaining, and any remnant grasses. Hopefully this will be able to be discontinued by the early dry season.

So........Monument may be a good option. Trials locally [ see photo - 8DAT showing the damage to narrow leaf carpet grass, the yellowish patch] have been impressive as a single pass option for weedy grasses in couch, as well as sedges. Locally, it is true that sedges tend to emerge most months of the year on irrigated areas, although peaking in the wet season. Get those wet season weeds, and big improvements can be made to reduce sedge levels, as there is much less emergence after April.

While not a perfect solution, using Monument has made a fantastic improvement to carpet grass in couch on this oval!

UPDATE - 24 February 2012

Carpet grass is Axonopus compressus or broad leaved carpet grass; narrow leaf carpet grass is Axonopus affinis just to ensure readers understand the issue.

Many curators / superintendents in north Australia still use glyphosate as a solution; metsulfuron may also be useful, especially on couch which is very tolerant of higher rates. It is a REAL issue in the wet tropical regions and especially broad leaved carpet grass thrives in wet soil / higher rain conditions, so better controlled irrigation management at a lower but adequate level can be part of the holistic management needed to get it under contol.

New and Old Herbicides - Tropical Turf

At last...............two new herbicides are available for use in tropical turf areas, especially zoysia turf. They may need to be purchased directly from national suppliers, as unlikely to be stocked in the NT.

The first is Drive - quinclorac is the active ingredient. Been around for a while, starting life as a crop herbicide with the name Facet. Active as both pre and post emergent, so will knock off emerged weeds and add a follow on pre-emerge control. Great for many annual grasses, and a few perennials too. Relatively few trials in the tropics of Australia, but some coming soon. Expect will be useful to control Bahia grass in both couch and zoysia, annual grasses and some hard to manage grass weeds. Will NOT control carpet grass.....period! Currently it is expensive, and in my opinion, very overpriced for an old product. BUT.......for some needs it is a great product and very effective. Has a lot of potential for widespread use in both zoysia and couch areas.

Next is Monument - a sulfonyl urea - and also reasonably pricey, but with the advantage of controlling both sedges and annual grasses in one package, it may be a suitable option. Work locally so far, shows fair results for carpet grass, with medium term suppression and some kill only, but excellent results for sedges and annual grasses. Rates are low - medium, depending on required outcomes, with higher rates required for grasses. Seems promising for tropical Australia.

Old herbicides do not get the advertising $$ once they are out of patent, but they can be effective. The products DSMA and MSMA are still effective for grass weed management in couch ovals or sporting arenas. BUT they need repeated applications, and unfortunately in the tropics it is never cool enough or [ for an oval] dry enough to fully eliminate the grass weeds it seems. They are also relatively poor options for carpet grass control, as they just cannot do the job!

Others though such as diuron and some of the triazenes can be a useful tool, at suitable rates. Be careful though, as some turf species do not tolerate these products.

Asulox will control carpet grass, but rates for use in turf are still to be worked out. It is a sugarcane product and known to have some potential. High rates will kill turf........it will be a balancing act to get rates correct. Currently Asulox is not registered for turf use

Ronstar - oxadiazon - is a very useful but expensive product for weed management while establishing couch or zoysia. Can be effective in Bahia grass, where grass contol options are more limited. Another oldie, but still goodie! Pity prices are still toooooooo high!

A good source of information is www.pestgenie.com.au . A great Australian web site focussing on agrochemicals for the Australian rural scene.

Take care with all agrochemicals and watch out for rain. Remember that in many areas, a good ally is the Met Bureau web site and the local radar. Quickly spots any likely storm clouds. For the Darwin area the link is www.bom.gov.au/weather/nt and go to radar image. Similar links are available in many other areas.