clovers, wild radish, bedstraw, bifora and self-sown pulses are particularly hard to control in lentil crops. While use of the herbicide tolerant varieties PBA Hurricane XT and PBA Herald XT might increase the herbicide options for weed control over conventional varieties, this does not over-ride the necessity for careful paddock selection and adequate weed control in previous years. Preventing seed set of broadleaf weeds in the year prior to growing lentil is very important.
It is essential to plan your weed control strategy before sowing. Delaying sowing is an option in most areas except the lower rainfall areas (below 350 mm). This strategy can enable several weed kills before sowing. Delayed sowing is practical for shorter season varieties like PBA Blitz and PBA Flash, but not for varieties that require a longer growing season.
Herbicides applied pre-sowing or post-sowing pre-emergent (PSPE), or a combination of both, can control many broadleaf weeds. Most grass weeds can be controlled either pre-emergent or post-emergent, with the exception of those with herbicide resistance.
Diflufenican products and flumetsulam are registered for post-emergent broadleaf weed control in lentil. Some caution is required as some varieties are sensitive to post-emergent herbicides. PBA Hurricane XT and Herald XT have increased herbicide tolerance to applied flumetsulam and residuals of some ‘SU’ and ‘imi’ products. Imazethapyr can be used only on PBA Hurricane XT and Herald XT under APVMA permit PER14369.
Refer to herbicide labels or seek professional advice for optimal weed control before and during the lentil season.
Avoiding herbicide damage
Pre-seeding herbicide applications are often considered safer and more reliable than post-sowing applications, particularly under dry conditions. To ensure weed control in the seeding furrow and to minimise crop damage, a combination of pre and post-sowing applications may be required.
Under adverse seasonal or soil conditions, most post-sowing, pre-emergent herbicides can damage lentil. Even post-emergent applications can cause crop damage in some circumstances. In most cases damage can be attributed to the product solubility and agronomic or environmental factors.
To reduce the risk of herbicide damage when using metribuzin or other soluble products post-sowing pre-emergent (PSPE) on lentil:
- sow at a depth of 5 cm or deeper
- apply the herbicides to a level soil surface (e.g. after prickle chaining or rolling)
- appreciate that rolling after press wheels may not do enough to level out the furrow
- avoid applying these herbicides post-sowing to dry soils
- choose the right herbicide rate for the soil type (lighter soils require lower rates than heavier soils – seek local professional advice)
- check variety susceptibilities
- consider splitting the applications between pre-sowing and PSPE.
To reduce the risk of herbicide damage when using broadleaf control herbicides post-emergent on lentil:
- as for PSPE for sowing depth (5 cm or deeper) and soil conditions
- apply post-emergent herbicides under warmer (>5 degree C) conditions during a period where some rain has fallen and there are no frosts.
See also 'Residual herbicide and weed control'.
Lentil can be successfully croptopped with paraquat to control seed set of annual ryegrass, however care with timing is critical. Croptop lentil as late as practical to minimise yield reduction but within the window of greatest effectiveness for preventing weed seed set.
Croptopping lentil too early can affect grain quality with green kernels and seed coat discolouration arising from premature desiccation. However, in prolonged growing seasons, the lentil crop may not be mature enough when the grasses are ready to be topped. Lentil variety choice based on maturity time can therefore be important. Varieties like PBA Bolt, PBA Blitz and PBA Flash are safer to croptop than later maturing varieties.
Ideally, the lentil plants should have finished flowering, have well-formed seeds in the pods and started to turn yellow/brown before croptopping commences. Bewa