Things to consider when applying weed control methods
Choosing the control measures for each weed type depends on the:
- characteristics of the weed
- characteristics of the environment we are working in.
1. The characteristics of the weeds:
Type of plant
If you wanted to kill monocotyledons (grasses, etc) but not dicotyledons (broad-leafed plants) you would use a selective herbicide. On the other hand, to kill all types of plants you would choose a non-selective herbicide. Note: Many of these herbicides are extremely dangerous to animals and humans. Chemicals should only be used as a last choice and not sprayed near waterways at all.
Stage of growth
Often it is desirable to prevent weeds germinating from seeds. This can be done by applying a pre-emergent herbicide to bare soil, which will kill the seeds. For germinated seeds and plants of all sizes, a post-emergent herbicide is used.
Season
The time a plant will set seed should also be taken into account. Ideally, plants should be controlled before they set seed to reduce their opportunity to spread.
Form or shape
Trees and shrubs: Large woody weeds, such as shrubs and trees, can be cut down using loppers, saws and chainsaws. Plants with lignotubers need the stump removed or poisoned.
Large clumping: It is often preferable to completely dig out large clumping plants with a mattock or shovel rather than spray with a herbicide. Plants with growing points below the surface (eg crowns, corms, rhizomes, or tufted or fibrous root systems) can be dug and levered out of the ground. Make sure the entire growing crown is removed.
Herbaceous: Shallow rooted herbaceous plants can be hand pulled. Plants with a large root system can be pulled out after a knife or trowel is used to dig down and sever the roots. Make sure you minimise disturbance by replacing the disturbed surface litter.
2. The characteristics of the environment you are working in:
Aquatic
When weeds are found growing in and near to water, avoid using herbicides as they are likely to wash away in rapidly running water. Choose alternative methods that have less of a negative impact on the environment, eg solarising kikuyu.
Riparian (waterside) area
Herbicides should not be used within 5m of a waterway. However, if you have to use a herbicide, then make sure you consider its effect on aquatic life and non-target species. Choose one that has been developed for use near waterways. Read the label and MSDS beforehand and follow your supervisor's instructions, the manufacturer's specifications and enterprise work procedures. Note: if weeds are physically removed, then bank stabilisation may be required to avoid erosion problems, eg matting, etc.
Beach and heath
These areas tend to be exposed to extreme conditions, such as strong winds. This can lead to blowouts and other forms of erosion. To avoid these problems, brushing or wind-breaking is necessary.
Roadsides, firebreaks and edges
Areas that are regularly disturbed or used by passing traffic are prone to reinfestation. They require regular monitoring and maintenance.
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