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Pre-emergent herbicides and their fit for your system

Annual Ryegrass long term management banner

The use of pre-emergent herbicides has been key to the long term management of Annual Ryegrass control in Western Australian cropping systems. A number of products representing different modes of action (MOA) are available for use in cereals including the likes of Boxer Gold (J & K), Sakura (K), Trifluralin (D) and Avadex (J). More recently there has been increased adoption of various tank mixes of pre-em products for a more robust approach to resistance management and to improve performance in our often uncertain environmental conditions around seeding time.

With no two seasons ever the same, the observed performance of different products can be attributed to the chemical properties of the active ingredients and their interaction with soil type, environment, seeding systems and the weed burden they are placed under.

Characteristics relating to a products solubility, adsorption to soil and organic matter, potential for volatilization and photodegradation, to name a few, all influence how a product will perform on your own farm and seeding system and from season to season. The Grains Research & Development Corporation (GRDC) has published a pre-emergent fact sheet worthy of reading to gain a better understanding of how the various active ingredients compare. It provides an insight into the advantages and limitations of each product and how they might fit your particular situation.

In many cases it might be that not one product fits all situations and requirements of your cereal cropping program. Crop type, rotational constraints, expected weed burden, resistance management, seeding logistics and likely environmental conditions are among just some of considerations when selecting what pre-emergent products you will use.

Many growers will use at least two pre-emergent products, Trifluralin and an alternative MOA product such as BOXER GOLD® or Sakura, however, it may be that each of these products, and possibly others, all have a fit across different parts of your cereal program. Understanding the strengths and limitations of the active ingredients of the products, used alone or in combination, will allow you to best decide what’s appropriate for your situation and provide some insight to the expectations of the products performance.

Syngenta has long been involved in pre-emergent herbicides and first introduced BOXER GOLD to WA growers in 2007. At the time it was the first alternative MOA to rotate with Trifluralin for resistance management of Annual Ryegrass. In addition to being a robust alternative MOA, BOXER GOLD (800 g/L Prosulfocarb & 120 g/L S-Metolachlor) has a number of other technical benefits:

  • No carry over. The residual characteristics of BOXER GOLD means there is no risk of crop injury in the following season so it has no plant back restrictions. This allows maximum flexibility in crop rotational planning. Particularly important when dry years occur and sufficient rainfall is not received to meet plant-back requirements of other products.
  • Enhanced knockdown performance. When applied in mixtures with SPRAY.SEED or glyphosate targeting 1-2 leaf ryegrass, BOXER GOLD has shown to increase knockdown performance by up to 19%. Weed growth stage and rainfall within 7 days of application will influence final control.
  • 7 day incorporation. With a low potential for loss due to photodegradation or volatilization, BOXER GOLD allows greater flexibility and improved efficiencies in seeding and spraying operations particularly compared to Trifluralin or triallate based products.
  • Application flexibility in cereals. BOXER GOLD provides the most reliable and consistent control of Annual Ryegrass when used pre-emergent at 2.5 L/ha incorporated by sowing (IBS). In situations where ryegrass is expected to germinate in the furrow wall (e.g. in non-wetting soils or high weed burden paddocks), BOXER GOLD can be applied at 1.75 L/ha IBS and then 0.75 L/ha PSPE. This use pattern can provide up to 8% improved control compared to all IBS applications but does rely on receiving adequate follow up rainfall.

    Alternatively, BOXER GOLD can be used at 2.5 L/ha early post-emergent (EPE) for suppression of 1-3 leaf ryegrass. This use pattern provides growers with existing Group A & B resistant ryegrass an additional tool for in crop control of ryegrass. Level of control is dependent on soil moisture conditions at time of application, follow up rainfall and Annual Ryegrass size at time of application. It is recommended this use pattern is used in combination with an effective pre-emergent herbicide.

  • Registered in wheat, barley & pulses. With its recent label extension for use in pulse crops, BOXER GOLD now allows growers to use an alternative MOA for resistance management in a wider range of crops including lupins, chickpeas, field peas, lentils and faba beans.

Figure 1.

More recently, Syngenta has registered ARCADE® (800 g/L Prosulfocarb) for control of Annual Ryegrass at 3 L/ha. ARCADE is an ideal tankmix partner with Trifluralin in wheat programs for robust resistance management (Figure 1.) Additionally, the absence of S-Metolachlor in ARCADE makes it a more suitable product choice for use on light soil types or disc-seeding systems where crop safety is important.