Spraying Crop Borders

Weed “rings” which often occur around the border of crop paddocks can lead to weeds moving further in, resulting in an increased need for spraying and most likely increasing the population of herbicide resistant weeds in the paddock.

Annual Ryegrass resistant to Glyphosate and other chemical groups on firebreaks and around the crop border is increasingly common.  Weed “rings” result in the spread of weeds with resistance to multiple herbicide groups further into the paddock.

Management of crop borders is not difficult, but requires time and attention to detail to be effective.

The aim of spraying crop borders is to prevent seed set of any weeds on the immediate margin of the crop.  Doing so prevents seeds from passing through the header and being spread further into the paddock.

Successful weed control on crop borders requires the following:

• Application of each crop herbicide out to the fence line. This maintains a consistent rotation of herbicide groups, widens the window for firebreak control and identifies any resistant weeds early.

• Rotation of knockdown herbicides (Glyphosate, Paraquat & Diquat).

• Inclusion of a residual herbicide such as Duiron, Atrazine or Simazine on firebreaks.

• Fallowing the outside rows of crop where high weed populations are present.

• Prevention of any escapes from setting seed. This may require a follow up application of Gramoxone or SpraySeed or cultivation.

• Application of contact herbicides to small weeds using higher water volumes.

• Application of residual herbicides to relatively bare ground.

Due to the toxic nature of SpraySeed and Gramoxone, application of these products from a bike sprayer is not ideal.  A designated, well setup firebreak sprayer with a good size tank increases effectiveness, efficiency and operator safety.  At a cost of $6,000 to $8,000 this is another cost, however it pales into insignificance compared to the cost of controlling herbicide resistant weeds or managing weedy paddocks in the future.