How to use Grazon^® Extra

The ‘Rolls Royce’ control option for foliar applications on hard-to-kill noxious and woody weeds. Containing three active ingredients, including the powerful proprietary active ingredient aminopyralid, Grazon Extra offers control of the broadest list of weeds in a single product on the market.

Grazon Extra offers outstanding knockdown and residual weed control.

For most weeds the rate of Grazon Extra to apply is between 350 and 500 mL per 100 litres of water.

Always check the label for the correct rate. A copy of the label can be accessed here.

If possible, mix Grazon Extra with clean water sourced from town supply or a rain water tank, although any source of clean water may be used. Avoid using water that is particularly ‘hard’ or strongly alkaline as that may reduce herbicide efficacy. Half fill the spray tank with water then add the Grazon Extra before adding the remainder of the water. If the product label requires the addition of a spray oil, penetrant or wetting agent to assist in control your particular weed population, mix in once the spray tank is full.

Once mixed, the spray solution should ideally be kept agitated and used immediately. However, if circumstances conspire to interrupt spraying, a mixture of Grazon Extra and water can be stored for up to seven days, provided that it is intermittently agitated each day, and well agitated again before use.

In general, smaller weeds are easier to control than large ones.

Grazon Extra is most effective when applied to weeds that are not stressed due to lack of moisture, excessive heat, insect or pathogen (such as rust) damage, etc. and are actively growing. Actively growing weeds will draw the chemical into the vascular system and transport it through the stems and down to the roots to ensure maximum efficacy.

A general guide to the best time of the year to treat common woody weeds can be found in this table.

Grazon Extra needs to penetrate into the leaves of treated weeds before any rainfall occurs so do not make applications if rain is possible before the spray is completely dry – usually one hour. Similarly, avoid application if the leaves are wet from rainfall or dew.

Once the weeds have been sprayed leave them undisturbed so that the chemical is able to move throughout the leaves, stems and roots and provide complete kill. Disturbing the weeds by slashing, burning, mulching, etc. before the chemical is fully distributed will compromise the control achieved. We recommend that blackberries and other woody weeds not be disturbed for six months after spraying to maximise the performance of Grazon Extra.

Apply as a foliar spot spray to completely wet all leaves and stems. Coverage should be to the point of run-off in that the chemical mix is just beginning to drip from the leaves once the spraying is completed. Think of painting a wall and use that motion in your spray action to achieve full coverage of the foliage, then use a more directed stream to thoroughly treat the stems and canes.

This type of application is called high volume spraying as you are applying a large amount of spray mixture to the target weeds. Provided that good coverage of the target weed is possible, high volume spraying can be completed using a variety of equipment – from a small hand pump unit to a knapsack sprayer through to a large motorised pump and hand gun unit.

With a foliar spray you are looking to capture enough chemical on the foliage to kill not only the above-ground portion of the weed but all of the root mass as well, so good coverage is essential. If you are spraying very large weeds like blackberries that are several years old, ensure that canes on the inside as well as the outside of the foliage mass receive direct contact with the applied spray.

As a guide, one hectare of blackberries 1–2 metres in height will typically require a spray volume of 3000–4000 litres to be thoroughly covered, whilst the same area of a small herbaceous weed such as ragwort will require 500–1000 litres.

A video demonstrating the correct techniques for high volume spraying can be accessed here.

1. Horses, goats and grazing stock destined for local markets

There is no grazing withholding period (WHP) for stock feeding in pastures in which woody weeds such as blackberries have been sprayed with Grazon Extra, provided the stock are not destined for slaughter for export markets and stock can continue to graze while weeds are being treated.

However, care does need to be taken because some treated weeds often become very palatable to stock, as there is an increase in the plant’s sugar content as it dies, and stock will preferentially graze on these over the pasture grasses. If naturally toxic weeds such as ragwort, variegated thistle and capeweed are being sprayed, stock should be kept from the paddocks until these weeds have died.

For further information on the use of Grazon Extra in areas around horses, the information in this technical note may be useful.

2. Stock destined for export markets

Stock destined for export markets should be prevented from feeding in paddocks sprayed with Grazon Extra for 42 days after application. Alternatively, stock can continue to graze treated pastures inside the 42-day period but must then be fed on clean feed (from outside the treated paddock) for at least three days before going to slaughter. (NB: The grazing WHP or ESI has nothing to do with market – but relates to slaughter.)