Farmers' 'bible' reveals new technology to beat winter weeds

Farmers' 'bible' reveals new technology to beat winter weeds


Cropping
Capeweed. One of the many weeds faced by croppers. Various herbicide options are covered in the recently released booklet for control of weeds like capeweed.

Capeweed. One of the many weeds faced by croppers. Various herbicide options are covered in the recently released booklet for control of weeds like capeweed.

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Bob Freebairn writes about the latest advancements in winter crop weed control technology.

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Herbicide technology has moved so fast in recent decades that it is always a challenge to keep up with constant upgrades.

The 2019 edition of Weed Control in Winter Crops, published by the NSW Department of Primary Industries and authored by agronomists Greg Brooke (pictured) and Colin McMaster, is nationally recognised as the "bible" of winter crop weed control technology, especially with regard to herbicides.

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What a contrast to my father's era, 2,4-D only became commercially available in the late 1940s with widespread use from the 1950s onwards, and it was the only available herbicide for use in cereals for several more years to come.

I well remember my father, Max Freebairn, who farmed all his life at Greenethorpe in Central West NSW, telling me skeleton weed almost ruined the wheat industry leading into the 1950s.

A broadleaf perennial weed, it sapped crops of nitrogen and water, including in the fallow period, and made harvest extremely difficult. 2.4-D fortunately controlled it well in winter cereals.

At this same time sub clover and superphosphate use became more widespread and addressed, to a major degree, nitrogen deficiency as well as competed strongly with the weed in the pasture phase.

Greg Brooke, one of the two senior NSW DPI authors of the recently released edition of the 'Weed Control in Winter Crops' booklet.

Greg Brooke, one of the two senior NSW DPI authors of the recently released edition of the 'Weed Control in Winter Crops' booklet.

Today, as the 2019 Weed Control in Winter Crops publication details, there are literally hundreds of different herbicide options available to crop growers with new ones, or new combinations of different chemical types, being released each year.

Equally important is the developing knowledge of strategies to manage herbicides to avoid weed resistance to them.

Even within a group (or type) of herbicides, a given weed can develop resistance to a herbicide, but not to another product.

One of the many features of the book is that it is easy to assess what herbicides are available for a given weed or group of weeds, what herbicide group a given product is from, at what stage to apply, and cost.

As a general rule it is best to rotate, from year to year, herbicides from different groups to avoid weeds developing resistance to a given product.

Some weeds develop resistance quickly to certain products if regularly used, whereas other products take much longer for weed resistance to occur.

One of the growing in importance features of the book, is possible residual life of a herbicide with respect to its likely adverse impact on following crops or pastures.

For example, a common situation I often see is poor survival of some pasture legumes sown a year, in some cases two years, after certain herbicides have been applied to a crop.

Drought years can especially lengthen residual life of some herbicides.

Changes in the 2019 updated weed control publication include Axial Xtra to replace Axil.

The new formulation contains a built-in adjuvant (which saves adding one) and is reported to add to faster brownout, improved control (weeds like wild oats, phalaris and annual ryegrass), improved compatibility with some other products, as well as a wide application window.

Rates per hectare have changed because of different active levels.

As a general rule it is best to rotate, from year to year, herbicides from different groups to avoid weeds developing resistance to a given product. - Bob Freebairn

Kamba 750 replaces Kamba 500, an active upgrade of dicamba percentage.

Rustler (propyzamide) has an extended registration that now includes use in pulse crops chickpeas, faba beans, field peas, lentils and lupins.

It is a grass control product incorporated by sowing (group D herbicide).

Sledge replaces Ecopar, but has changed application rates because of higher active concentration (pyraflufen-ethyl).

Sledge is used in various situations including prior to sowing a winter crop, starting a winter fallow or fallow use.

Archer 750 has an increased level of clopyralid.

Intercept is a product now registered for use in 3-leaf imi-tolerant barley.

Roundup Ready has reduced active load from 640g/kg to 540g/L.

Booklets are available complimentary from Local Land Services officers or the NSW DPI (www.dpi.nsw.gov.au).

Next week: Strategies to overcome lack of legumes in perennial pastures.

I will write about the increased productivity of perennial pasture grasses such as natives, temperate perennials like phalaris, and tropical grasses when they coexist with legumes or if their nitrogen supply is added to via fertiliser.

  • Bob Freebairn is an agricultural consultant based at Coonabarabran. Email robert.freebairn@bigpond.com or contact (0428) 752 149.
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