. 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. Beware of the potential for coloured foam marker dyes to stain lentil seed inside the pods.
Take note of the harvest withholding periods of the products used so that harvest does not need to be delayed because of product withholding periods. For paraquat the withholding period is 7 days on most labels. Crops that have been croptopped are more prone to seed staining after rain than crops that have been desiccated.
Weed wiping is being successfully used in lentil to prevent weed seed set of herbicide resistant ryegrass and other weeds. For weeds wiping to be successful, the in-crop weeds must be taller than the lentil plants, and any standing stubble) at the time of wiping.
A weed wiper can be useful to prevent seed set of tall weeds in lentils.
Lentils do not compete well with weeds but they do offer a variety of weed control options in the rotation.
Preventing seed set on all ryegrass escapes is the aim when croptopping in lentils.
The main diseases of lentils in Australia are ascochyta blight, botrytis grey mould and viruses. Integrated disease management in lentil requires the use of the following strategies:
- Paddock selection. Aim for a break of at least three years between lentil crops and at least 250 m from the previous year’s lentil paddock. Avoid sowing lentil in paddocks adjacent to faba bean, vetch, chickpea or lathyrus stubble as these crops can hosts diseases that affect lentils.
- Variety selection. Select varieties that are least susceptible to the main disease risk for the region. Sowing more than one variety spreads the overall risk.
- Seed source. Use seed from a paddock where there was no weed seed contamination and where no viruses and fungal diseases were previously detected. A fungal threshold of less than 1% is acceptable. For viruses, a threshold of <0.1% seed infection is necessary in high risk areas, and <0.5% seed infection for low risk areas.
- Seed treatment. Treat seed for sowing with a fungicidal seed dressing.
- Canopy management. Manipulate variety choice, row spacing, seeding rate a