Grubbing and cultivation
Grubbing and cultivation can be used to control many annual weeds that are present as isolated plants or in small patches.
Perennial weeds that do not have an extensive root system can also be removed in this way. However, some perennial weeds, such as silverleaf nightshade and skeleton weed, are spread by cultivation, due to the ability of cut pieces of root to regenerate, as well as regeneration of plants from below the cultivation depth.
External video: GRDC: mouldboard ploughing pros and cons.
External video: Brisbane City Council, complete weed removal.
Mowing and slashing
Mowing and slashing are effective ways of controlling many annual thistles, but the timing of the operation is important. It is best carried out between the budding stage and first flowers. If done earlier than this, there is a risk that the severed stem will produce a new flowering shoot. If carried out later than early flowering, the cut portions of the plant may contain enough moisture for some of the immature seeds to reach maturity and become fully viable.
External video: Brisbane City Council, mowing and slashing.
Burning on its own is of limited use in controlling weeds. However, it is a useful preliminary operation in the control of cape tulip. Burning destroys the surface trash and allows the maximum amount of water to penetrate the soil early in the season when ground temperatures are still warm, which stimulates a high proportion of the tulip corms and cormils to sprout.
Burning is also useful in destroying the dead canes after treatment in clumps of blackberry, thus thinning out the stand and making it easier to spray effectively in the following season. Burning mature cotton bush encourages dormant seeds to germinate. If the resulting seedlings are destroyed by other methods this will reduce the time required to control the weed. The burning of mature cotton bush also stimulates a pathogen to attack the base of the stems and cause rotting to set in.
External video: GRDC, weed seed bank destruction, burning chaff dumps.
Grazing can destroy weeds or reduce their capacity to compete with pastures or produce seeds. Sheep especially will seek out and eat seedlings when there is no other green feed available. They are particularly effective in destroying paddock infestations of kochia and gorteria. Paterson’s curse can also be effectively controlled by heavy grazing. In fact, many badly weed infested paddocks result from poor pasture utilisation. Goats are particularly effective in grazing woody plants and also removing flowering heads from thistles.
External video: GRDC, chaff-fed sheep help break weed cycle in York.
Spray-grazing and spray-topping
Spray-grazing and spray-topping are weed control techniques that exploit the weed-killing potential of large numbers of stock grazing an infested pasture previously sprayed with a sub-lethal quantity of certain herbicides. Weeds sprayed with a sub-lethal dose of a phenoxy, hormone type herbicide appear to be more palatable to stock.
External video: MLA, grass seeds tutorial, spray topping.
Competition between plants is important in the control of seedlings. In Western Australia pasture competition is mainly important in the control of winter-growing weeds because most of our pastures are based on winter-growing annuals. Seedlings of doublegees, Bathurst burr and skeleton weed are very sensitive to competition from other plant species.
External video: GRDC, crop competition for weed management, narrow row spacings.
Further information on controlling declared plants can be found through the Declared plant control handbook link.