nd time of sowing to manage crop height, delay time of canopy closure and prevent lodging to assist in disease management. Wider row spacing (23–42 cm) delays canopy closure and may reduce disease, provided lodging does not occur. Standing cereal stubbles help to keep lentil plants erect but could enhance botrytis grey mould (BGM) development if stubble remains wet for long periods (e.g. 4–5 days). High humidity and excessive rainfall during the vegetative growth phases also could enhance the development of BGM and reduce seed quality.
- Sowing rate and depth. Target plant density should be 120–150 plants/m2. Aim for higher density populations for lower rainfall areas and short season environments. An ideal germination percentage is 80%, if less, sowing rates may need to be increased to compensate.
Seeding rate (kg/ha) = Plant density (plants/m2) x 100 seed weight (g) x 10 ÷ Germination percentage
Sowing depth should be 4–6 cm. This depth protects seed from herbicide damage and offers an optimum environment for rhizobium survival. Make sure there is good soil moisture before sowing and that seed has been inoculated.
- Sowing date. Sow within the optimal planting window for the district.
- Hygiene. Take all necessary precautions to prevent the spread of disease between paddocks and farms.
- Foliar fungicide program. Foliar fungicide applications often commence before canopy closure. Use the spray program for foliar fungicides provided below to assist in making fungicide application decisions. Success depends on crop monitoring, correct disease identification, timeliness of application and use of the correct product.
- Harvest management. Early harvest minimises disease infection on seed.
See also 'Meeting lentil market requirements'.
A BGM susceptible variety (front centre) showing botrytis grey mould compared with the same variety (immediately behind) treated with fungicide and other varieties (left and right) that have resistance to BGM.
Ascochyta lesions and leaf necrosis on lentil leaves.
Ascochyta staining on lentil seeds.
An integrated disease management plan should include a well-planned fungicide program.
Virus patches in lentil. Note initial infection area (dead plants) and newer infections nearby.
Beet western yellows virus (BWYV) in lentil.
Lentils with CMV and AMV. Note the bare ground surrounding the plants.
Ascochyta blight is a potentially serious but manageable disease of lentil in Australia. Most current varieties are unlikely to have significant yield losses due to ascochyta blight. However, ascochyta blight does infect lentil pods and seed, causing a discolouration of grain that will significantly reduce the marketability and value of affected grain.
Symptoms of foliar infection
The disease (caused by Ascochyta lentis) appears on leaves and pods as round, whitish lesions with brown margins. Black fruiting bodies in the lesions distinguish the disease from spots caused by herbicide damage. Severe infections cause leaf yellowing. Tips of stems wilt, turn brown and die. Pod infection spreads to the seeds, which turn purple-brown and shrivel in whole or in part.
Ascochyta blight can be both seed and stubble borne. Wind borne spores from infected lentil stubbles can blow into adjacent paddocks and infect new lentil crops. Infection can occur at any stage of plant growth, but is more significant during late flowering and pod fill. Wet weather favours disease development and rain splash spreads spores onto new crop growth within the crop, including pods.
Ascochyta blight management begins with the use of disease-free seed. Test retained seed if there is any doubt about the disease status of the seed. Sow into paddocks that are free of infected lentil stubble and avoid close rotations of lentil in the same paddock. Sow a variety that is resistant (R) to AB seed infection such as PBA Jumbo2, PBA Herald XT and PBA Ace. Moderately resistant (MR) varieties are PBA Hurricane XT, PBA Blitz, PBA Bolt and PBA Giant. For other varieties, strategic fungicide sprays may be required during flowering and pod fill.
Fungicida