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The importance of having a robust herbicide program


By Scott Mathew, Senior Technical Services Lead

If you have found that your vineyard has weeds resistant to knockdown herbicides or you think that there is a chance of herbicide resistance, or you have simply used the same knockdown herbicide product or Mode of Action (MoA) group over the years, it’s definitely time to look to introducing a more robust strategy.

An over-reliance on a single herbicide group will inevitably lead to a change in the composition of your weed population, leaving behind harder to control weeds or worse, herbicide-resistant weeds.

As a grower, you could benefit from incorporating a pre-emergent herbicide with different MoA into your weed management program, particularly if a key weed target is Annual Ryegrass (Lolium rigidum).

Pre-emergent herbicides control weeds at the early growth stages between weed seed germination (root-shoot emergence from the seed) and seedling leaf emergence through the soil. The residual activity of the herbicide when incorporated into the soil can control the several flushes of germinating weeds. Rain or irrigation is needed to incorporate the herbicide into the soil.

Application of a pre-emergent herbicide for control of a weed like Annual Ryegrass should be planned for autumn—prior to when the bulk of the Annual Ryegrass seeds will germinate.

The good thing with incorporating pre-emergent herbicides into the program is that there are lots of options and Modes of Action to choose.

Pre-emergent vineyard options include:

  • Group C: simazine (GESATOP)
  • Group D: oryzalin, pendimethalin
  • Group F: norflurazon (Zoliar)
  • Group G: oxyflurofen (Goal)
  • Group K: napropamide (Devrinol)
  • Group O: isoxaben (Gallery)

The pre-emergent group of chemistry or Mode of Action that best suits your situation will largely be determined by the known weed spectrum, soil types and herbicide history.

Areas to be treated should be free of weeds and excessive mulch. If weeds are already growing in the area to be treated, an appropriate knockdown herbicide should be applied either before or, if compatible, combined as a tank mix with the product. Many pre-emergents have limited to no knockdown ability of their own.

Selecting the right product to control the weed spectrum present at the right time is important and can reduce the need to apply multiple knockdown herbicides during the season. So, I suggest that you sit down with your adviser and map out the program. It will be time well spent.