For most pastoralists the task of keeping pastures free of woody weeds is a demanding activity that requires constant vigilance and attention to detail.
The list of woody weeds that invade crops and pastures in Australia is long and diverse. More than often, they are perennial invaders and well-adapted to survive adverse conditions. Many produce fruits and seeds that can spread over long distances by water, birds, rodents and animals, their seeds are able to survive in the soil for long periods.
We discuss some of the many aspects involved in the control of woody weeds below.
Pasture management
The competition effect from a healthy pasture makes it more difficult for invasive weeds to become established. They often spread from areas of diminished competition - for example around watering points. Frequent inspection and early intervention in such areas will prevent further spread of weeds later on.
Prevention vs cure
Small clusters of invasive woody weeds can usually be eradicated with herbicides alone. However, large uncontrolled areas of growth may require mechanical intervention in the form of slashing, ploughing, dozing or chains – followed by chemical treatment once easier access is possible. Mechanical control serves to improve access to impenetrable growth of invasive weeds and is often the first step in the eradication process. This may however, also have unwanted impact by fragmenting the plant or roots from which prolific re-growth may occur, and for which a soil residual herbicide may be required.
Timing of chemical control
Depending on the plant species and where in Australia they grow, the best timing for application of herbicides may vary. Each weed is different, and it is important to understand its respective biology when deciding when to spray. As a general rule, best results from herbicides will be achieved when the plants are actively growing, not under stress or heavily grazed, and when mixed with a suitable adjuvant to enhance its performance.
The growing environment
It is not unusual for woody weeds to grow under or among trees or other desirable vegetation. In such cases, the choice of herbicide should be determined by its potential impact on the non-target plants.
Herbicide labels
Product labels are an authentic source of information about which product to use to control specific weeds, how to apply it, and detailed directions for use. Most labels would recommend the use of an adjuvant to enhance its performance, including some of the products discussed below.
Brushwet is a popular organosilicone penetrant for use with a range of herbicides including glyphosate, clopyralid, metsulfuron-methyl and sulfosulfuron-metyl for control of brush or woody weeds. It is a non-ionic surfactant with superior spreading and penetration qualities to promote uptake of the herbicide active ingredient on difficult-to-wet foliage.
Glysowet Surfactant is a suitable choice when the use of a non-selective herbicide like glyphosate is required. It is a tallow-amine based adjuvant that is compatible with 360 g/L, 450 g/L and 840 g/kg glyphosate formulations.
Wetout Spray Adjuvant ia a great alternative for environmentally sensitive situations where a greater degree of spray drift control and biodegradability is required. It is also recommended for use with glyphosate formulations but can also be added to paraquat and diquat products, phenoxy herbicides, soil residual, and selective herbicides. Wetout is a highly concentrated adjuvant with low use rates that helps to reduce spray drift.
Spreadwet 1000 is another concentrated adjuvant that is registered to be mixed with soil residual herbicides for control of plant or roots fragments after mechanical breakup.
Regardless of the weed to be controlled, growing situation or herbicide used, Envirodye Red Liquid Marking Dye is an indispensable addition to any brew for control of woody weeds. It is a liquid dye for use with herbicides to enable clear identification of sprayed areas – to prevent any misses or over-spraying. Envirodye Red is environmentally friendly and suitable for use in sensitive areas.
This article was written by DKSH Agrisolutions for Seasons magazine.
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