Top 10 tips - for grass-weed control
Increasingly complex grass-weed problems mean it is essential to use pre-emergence herbicides, but along with increasing efficacy comes increased risk. Paying detailed attention to planning and executing a pre-emergence herbicide programme will help you maximise the reward while minimising the risk.
Choosing your products: Mixing or “Stacking” pre-ems can significantly increase herbicide performance but can also increase the risk of crop damage
1: Choose the most effective product as the basis of your grass-weed control programme
– Don’t compromise your pre-emergence grass-weedcontrol as subsequent spray opportunities may be limited by the weather 
2: Choose an effective product with the least potential to damage the crop in the event of adverse conditions
– BEWARE some actives are potentially more damaging to the crop than others
3: Consider tank-mixing pre-em products to enhance your initial level of control
– BEWARE tank-mixing actives may increase the risk of crop damage above and beyond that for the individual products
– BEWARE some actives have varietal restrictions
– BEWARE some actives have increased potential to damage crops if they are emerging at application
– If in doubt, check with your agronomist
4: Prepare a fine consolidated seedbed
– Seedbed quality will impact both on the efficacy and crop tolerance to your pre-emergence treatment
– If required, roll the seedbed before your pre-em application
5: Remove excessive straw or trash
– Control provided may be reduced if the applied pre-em does not make contact with the soil surface
6: Ensure appropriate sowing depth
– Check the label, most products require at least 32mm sowing depth into a consolidated seedbed
7: Apply your pre-em product at a pre-emergence timing
– The efficacy of most pre-emergence products declines substantially if applied post-emergence of the target weed
– Crop tolerance to some products is reduced when applied once the crop is emerged
– Aim to apply within 48 hours of drilling
– Whilst the efficacy of pre-em products may be reduced during prolonged dry periods the control provided is typically greater than that given by a delayed application to emerged weeds
8: Ensure even coverage of the soil surface
– Apply appropriate spray quality and volume to ensure even coverage of soil surface in order to maximise efficacy
– Pay particular attention to maintaining the correct boom height if seedbed is uneven or cloddy
– Avoid overlapping spray swaths to reduce potential for adverse crop effects
9: DO NOT apply when soil or weather conditions are not suitable
– DO NOT use on waterlogged soils as efficacy and crop tolerance will be compromised
– DO NOT use on very light soils as crop tolerance may be reduced, particularly if there is heavy rain soon after application
10: DO NOT cultivate or disturb the soil surface after application of your pre-em
– Disruption of the treated soil surface will reduce control
After you spray:
Even with the best planning, the conditions following application (especially heavy rain) can be conducive to crop damage, but this is normally transitory and the crop will recover with no long-term adverse effect:
