EARLY-SEASON FIREBREAK SPRAYING
Traditionally, firebreak spraying has been considered a low-priority late-season job. However, with a growing number of populations of hard-to-kill weeds such as annual ryegrass, spraying fence lines in late autumn should be a serious consideration where possible. By spraying fence lines early, growers can target small weeds and maximise the effectiveness of residual herbicides by targeting bare ground.
The following table outlines residual herbicide options which can be used for fence line spraying. It is important to note that the options listed in this table should be applied to relatively bare fence lines with a low density of small weeds. Listed prices are applicable to the time of writing. Rates are listed on a per hectare basis and assume a water rate of 100 L/ha.
Whilst the use of herbicides on fence lines can be quite effective, as always, an integrated weed management approach needs to be considered when managing weeds on fence lines. Physical/cultural weed control options on fence lines might include:
· Sowing close to the fence line.
· Cutting and baling weed ridden crop adjacent to the fence line.
· Removing fences and sowing through the old fence line (where possible).
· Slashing fence lines (may require multiple passes).
Another key component to integrated weed management along fence lines includes rotating the knockdown herbicide being used in the tank-mix. By spraying fence lines early where weeds are generally smaller and less dense, contact herbicides such as Paraquat and Glufosinate will likely be more effective. This then presents the opportunity for growers to rotate to these active ingredients and decrease their reliance on Glyphosate. Other knockdown herbicides which might be considered in combination with either Paraquat or Glufosinate include Amitrole and Group 14 herbicides (e.g. Voraxor or Terrador).
Ultimately, mixing and rotating the chemical modes of action used to control weeds on fence lines in conjunction with physical/cultural control options, will help decrease the incidence of herbicide resistance and prolong the effectiveness of key herbicides such as Glyphosate.