Wednesday, 17 December 2014

Nurturing newly-sown pasture and targeting brushweeds


Weed control in newly-sown pastures is important to help establishment of ryegrass and companion species like clovers, chicory or plantain.

There are several weed control options for ryegrass/clover mixes. An MCPB/MCPA mix, (Pasture Guard Nurture), is good for control of seedling thistles, buttercups, and a range of other broadleaf weeds such as fathen, nightshade, hedge mustard and shepherd's purse.

Tank mixing with flumetsulam (Aim) will improve control of other weeds such as chickweed, creeping yellow cress, mallow, oxeye daisy, sorrel, stinking mayweed and wireweed. Flumetsulam is one of the few herbicides than can be safely used over seedling chicory but some trial data shows it can be too damaging for plantain seedlings. Bentazone is also useful in many new pasture situations, but can be too damaging for chicory seedlings.

It is equally important to look after established pastures. Late autumn – early winter is a common time to control seedling weeds in pastures with broadcast applications, but spot spraying through summer can be an economical and effective way of controlling a wide range of weeds in pastures, including brushweeds.

Eliminate Brushkiller (Triclopyr+picloram) is a grass-friendly option that controls a wide range of broadleaf and brushweeds. For thistles clopyralid (Multiple) is also a very good grass-friendly option, and ideal for weed wiping Californian thistles, which is a great way of getting this perennial weed under control. Metsulfuron and Glyphosate can be low cost options for some weeds, but need to be used carefully to minimise pasture damage.

For summer or winter forage crops, we looked at pest control during establishment in the spring newsletter. Once forage brassicas are established, aphids and caterpillars can become an issue. Early sprays of Toppel 500 will usually clean up any aphids present, but once the crop reaches more advanced growth stages and particularly if aphid numbers are high, a systemic product such as Rogor can be more effective. For white butterfly and diamond back moth caterpillars, Halex can provide good control, and if aphids need to be controlled at the same time, Halex can be tank mixed with Rogor. Because brassica leaves are hard to wet and good spray coverage is important for control of insect pests, it is recommended to use a good quality surfactant, such as Widespread 1000.

Ignoring brushweed issues can lead to more expensive solutions. The spraying season for brushweeds usually runs from November to March, because brushweed herbicides work best during periods of active growth. It is important to take a programmed approach to controlling brushweeds.

Good fencing and water supply is required for good grazing management, which is an important part of controlling seedlings. Often it is advantageous to go through one or more shorter rotation pastures or crops to get the brushweeds under control and allow time to get soil issues rectified, before attempting to establish longer term pastures.

George Kerse is Product Manager, Agrochemicals at Ravensdown.

Options for aerial or spot spraying brushweeds include:

• Metsulfuron, (Eradicate 600), a lower cost option and very good for controlling weeds such as gorse, blackberry, manuka and matagouri, but does have a weakness on broom. Metsulfuron will damage productive pasture species such as ryegrass and white clover, however some pasture grasses, e.g. browntop, are tolerant. Metsulfuron also has some persistence in soil so sufficient time needs to be allowed before it is safe to sow new crops or pastures.

• Triclopyr (Eliminate) or triclopyr/picloram (Eliminate Brushkiller) mixtures have the advantage of being “grass friendly” and will control a wide range of brushweeds, including gorse and broom, but do cost more and are damaging to clovers. They are also a grass friendly option for spot spraying a wide range of broadleaf and brushweeds in pastures.

Glyphosate can be useful in some situations, particularly for controlling seedlings prior to oversowing.​