Australian wine is well known for its quality and reliability and the Australian wine industry are world leaders in innovation and quality control. The maintenance of its reputation increases pressure on the vineyard managers to stay well within the allowed limits for the use of pesticides.

As such weed control in vineyards becomes relatively complicated with a limited range of herbicides being used.

Current management strategies have led to increasing levels of herbicide resistance and incidence of hard-to-kill-weeds.

Adding to the limited number of herbicides that are acceptable, under-vine spraying is often left until spring when weeds are large with healthy root systems. Good spray coverage then becomes difficult. Add to this a number of issues with sprayer setup can lead to highly variable weed control.

Another complication with wine grape production is the encroachment of suburbia as towns expand and get closer to areas of agricultural production. Residential developments in wine growing areas are also popular, with a mandatory golf course attached. This increases the pressure on Vineyard managers to reduce the risks of pesticides going where they should not.

To put all this in perspective wine grape growers have their fungicide applications well sorted which is understandable because fungal disease has the greatest effect on grape yield and fruit quality in wine grapes. Weeds on the other hand have a much smaller effect on the production of high-quality grapes.
Important factors in high levels of weed control are understanding how different herbicide modes of action work which then determines how they need to be applied to optimise their effectiveness. The questions we need to ask are:

  • What kind of target are we aiming at?
  • What kind of droplets are most appropriate to hit this target?
  • What does the product do once it deposits on the target?

Table 1 below shows the number of spray droplets per square centimetre and per cent area coverage for different pesticide types.

Source Syngenta

The per cent area coverage is most easily measured using water sensitive paper and the SnapCard® app.

To check what pesticides can be used in wine grape production get the Australian Wine research Institute “Agrochemicals registered for use in Australian viticulture” or commonly known as “the dog book” which is also available as app.

https://www.awri.com.au/industry_support/viticulture/agrochemicals/agrochemical_booklet

Knockdown herbicides that are permitted for use in wine grape production are listed in Table 2. This table shows the behaviours of the different herbicide modes of action. Glyphosate is highly translocated and therefore very forgiving in application technique whereas paraquat is the opposite. Products like paraquat that are translocated need much higher levels of coverage therefore product rate and application volume are critical for high levels of weed control.
Seedling grasses smaller than 3 leaf make a challenging target so it is important to keep the application volume up to ensure there are enough droplets to hit the target.

Table 2 Knockdown / Non-selective herbicides (Click on the image to view the table).

A small number of selective herbicides are allowed and often used in the inter row area. Most of these herbicides are poorly translocated and also need good coverage to be effective.

Table 3 Selective herbicides (click on the image to view the table).