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A spring plan to tackle weeds

dried grape trees

Many growers are ‘out and about’ in winter spraying glyphosate under dormant vines for winter weed clean-up. A herbicide ‘double-knock’ is worth considering at this time of year to stave off weed resistance to herbicides; a growing problem in Australian vineyards. The double-knock utilises two different herbicide Modes of Action and, generally, involves applying glyphosate followed by either GRAMOXONE® or SPRAY.SEED® five to ten days later.

Both GRAMOXONE® and SPRAY.SEED® can be used under vines. Both are non-selective contact bipyridyl herbicides that belong to the Group L herbicide group. Where each one should be used really depends on the weed spectrum. GRAMOXONE is more suited to where annual grasses are more prevalent. SPRAY.SEED, which is a mix of the paraquat in GRAMOXONE along with diquat which does the ‘heavy lifting’ on broadleaved weeds, should be used where more annual broadleaved weeds are present - for example capeweed or erodium species.

Being contact herbicides, water volumes and spray coverage are very important with these products. Calibrated sprayers with flat fan jets adjusted to a height to give a double overlap of the spray at the top of the weeds being sprayed are ideal. Spraying pressures should be in the range of 200 to 300 kPa and you should select nozzles that give droplets in the 200 to 250 micron volume median diameter range at these pressures. Speed of travel should be in the range of 6 to 10 km/hr. Good weed coverage with the spray is essential, so adjust the water volume according to density of weed growth.

Going into spring, perennial grass weeds can become an issue, but none are more competitive than couch grass. Some growers tackle couch with repeated applications of glyphosate. This is often not the most effective way to deal with this weed. The first glyphosate application may work on the lush new growth, but doesn’t work too well on old rank growth. With the old rank growth still there to feed it, the plant slowly recovers requiring a second application, most likely with the same result.

The best way to tackle couch grass is to hit it in spring with a non-selective contact herbicide like SPRAY.SEED. It controls many small annual weeds and burns back the green material on the couch. Lack of green photosynthesising leaf area shocks the couch and stimulates it to send out new growth as a survival technique. The stolons and rhizomes send out new roots and shoots, resulting in a flush of even, lush new growth.

It’s here that you really need the reliability of a couch specialist and they don’t come any stronger than FUSILADE FORTE®. By making the couch produce all of that young active growth at the same time, you maximise your herbicide uptake and efficacy. FUSILADE FORTE is a systemic grass selective herbicide, so it can be used in and around vines with a high degree of selectivity.

Finally, resist the temptation to cultivate the soil for couch grass control. Cultivation buries the couch stolons and rhizomes at different depths, reducing the evenness of the new growth. It also chops up the roots and spreads rhizomes down the paddock that simply reshoot to form another patch. Obviously, you are looking to avoid this.