Effective weed control is essential for good yields and to avoid the build up of troublesome weeds in the rotation. Plan your weed control strategy before sowing.
Summary of an ideal weed control strategy:
- Where practical, delay sowing to maximise weed kill from knockdown herbicides.
- Maximise the effectiveness of the pre-emergent herbicide simazine by incorporating in wet soil.
- Ensure an even crop so that all plants are at the correct growth stage when post-emergent herbicides are applied.
- Spray small weeds early for an effective kill.
- Use the highest registered rate of post-emergent chemical possible without causing unacceptable crop damage.
- Crop-top with Gramoxone® or Reglone® if required.
Simazine is most effective when incorporated thoroughly into the soil. This is best achieved by applying simazine before the "break" so it will be washed into the soil by the opening rains and then sowing the lupin crop into the wet soil.
Caution: While simazine is most effectively applied before the opening rain it is unwise to commit too many paddocks to lupin in case of a late break.
Soil type will influence the maximum rate of simazine (600g/kg a.i) that can be applied. In Western Australia, 0.83-1.7L/ha is registered on light soils. 1.7-2.5L/ha is registered for use on gravely loam soils.
- On deep white, grey and gritty sands simazine can damage lupins at low rates (0.8L/ha or less).
- On yellow sandplain soils, crop damage may be observed at 1.25L/ha
- On loams gravely loams and sand over clay simazine rates 1.5L – 2.0L/ha can generally be used with good crop safety.
Trifluralin can also be added if grass weeds are expected to be bad.
Many weed populations have some tolerance to post-emergent herbicides.
To control these weeds apply post-emergent herbicides early and use the highest registered rate possible without causing unacceptable crop damage.
- Spray small weeds early
- Apply top-up simazine, diflufenican, picinolinafen when radish has 2-6 leaves.
- Target radish smaller than 250mm diameter with metribuzin.
- Use Eclipse® for controlling radish larger than 250mm.
- Target ryegrass before tillering.
- Crop timing
- Use metribuzin on tolerant varieties, PBA Gunyidi and PBA Barlock, when plants have four leaves until bud emergence.
- Use Eclipse® when plants have eight leaves until bud emergence.
- Crop-top when 80% of leaves have fallen off the lupin plants.
- Gramoxone® is registered at 400-800mL/ha for ground application only.
- Reglone® is registered at 1-2L/ha for application by a mister and plane as a harvest aid.