Weed Control in Pasture – the importance of controlling weeds early. Planning a weed control programme for new grass will help you grow strong, healthy and persistent pasture.
- Control all perennial weeds in perennial pastures is ultra important.
- Select a herbicide appropriate to the weeds, pasture species and size.
- Aim to spray the weeds before they get six true leaves, don’t let them get too big and get in a salvage situation.
Short term: Seedling weeds vigorously compete for nutrients, moisture, light and most importantly, space. Early removal of these weeds allows for more rapid and even establishment resulting in an increased amount of dry matter for your stock.
Long term: Poor establishment of newly sown pasture results in a decrease in pasture productivity and an increase in chemical costs from the extra weed control requirements down the track.
Ideally, you need a herbicide that will not damage the newly established pasture while providing effective weed control.
- The best time to spray weeds in new pasture is 4-8 weeks after sowing, prior to the first full grazing.
- Weeds are small & there is approximately 70% pasture cover
- Identify the main weeds present in the paddock and check the label to confirm they will be effectively controlled.
Spray grazing is an excellent and cheap option to control broadleaf weeds with phenoxy type herbicides including 2,4-D amine & MCPA amine.
- Spray weeds at the small rosette stage using lower rates of chemical (compared with spring).
- Clover should have at least 3 trifoliate leaves to avoid damage to younger plants (see more below)
- Graze hard 7-10 days after spraying (check chemical withhold periods)
- The effect of the spray begins to diminish after about 14 to 20 days post-spraying
IMPROVING THE KILL OF BROADLEAF WEEDS
Selective additions to your post-emergence herbicides (i.e. 2,4-D amine, MCPA amine) can lead to the improvement the control of certain broadleaf weeds including marshmallow & chickweed.
- Cheaper option than buyer broader spectrum herbicides.
- Highly versatile & can be used in knockdown activity or post emergent control
- Fast acting contact herbicides and aid in control of weeds through a process of membrane disruption
PASTURE MIXES WITH CLOVER OR HERBS
In many cases the broadleaf constituent of your pasture mix (clover or herbs) must be big enough for the spray to be used.
- Selective herbicides should be used, and can include Flumetsulam, pyraflufen-ethyl or haloxyfop.
- Some temporary clover suppression may occur, but recovery is rapid.
- Avoid high rates.
ATTACKING WINTER GRASSES
As we move into winter, a range of winter grasses dense up to fill in bare patches. It’s ultra important to keep on top of winter grasses in new perennial pastures as they compete for space & nutrients.
- Selective herbicides can be applied as pre-emergence and post-emergence in areas of aggressively growing winter grasses.
- Poa Annual matures quickly and seeds profusely making them an agressive weed difficult to control.
- Grazing or mowing is ultimately ineffective in their control as they begin to choke up your pastures.
- Herbicides can be expensive, however the potential cost of pasture DM lost in late spring & summer far outways the cost per hectare of spray and application.
All too often we get calls from farmers who haven’t got onto the weeds early enough and then need to salvage the situation. This poses a number of problems. Firstly, by letting the weeds get too big the damage is already done as far as effecting the establishment of your pasture. Having to spray big weeds, you need more robust chemistry that won’t be as clover safe and reduces the performance of your establishing pasture. If not controlled now they will substantially reduce the quantity and quality of spring pastures, be much more expensive and difficult to control, and hinder fodder conservation.
Disclaimer: Always read product label prior to use to confirm tolerance of species. Observe Withholding periods to grazing or cutting for stockfeed or harvest. Always refer to the label for specific rates, directions for use, crops and adjuvant requirements. Consult with your agronomist or chemical company as listed below.