Pulse Disease Guide 2013

In general, foliar diseases of pulses were common early in the 2012 season but, in most situations, failed to develop due to the dry spring. The major pulse disease issues in 2012 were chickpea crops dying out in patches and bacterial blight in field peas. Aphid numbers were low during the 2012 growing season, and viruses were of little concern.

Following a dry spring in 2012 carry over of pulse disease on stubbles and volunteers is expected to be low in 2013. However, be aware that bacterial blight is a seed-borne as well as stubble-borne.

Pulse review

Chickpeas: The main disease issue for chickpea crops was yellowing and dying out in the spring. As few viruses were detected in 2012 the problem was most likely caused by an interaction between soil-borne pathogens like Phoma and agronomic factors that weaken plant roots such as herbicides, shallow sowing, compaction, hard pans or anything that may inhibit root growth.

Symptoms became apparent in the spring when temperatures increased and the soil dried out. Plants with damaged root systems were unable to take up water, so they started to die from the base upwards.

Ascochyta blight was detected in a number of crops during 2012. Chickpea varieties rated as moderately resistant to ascochyta blight may require a foliar fungicide application to protect foliage. An application at podding is necessary to reduce seed infection and yield loss, in all varieties.

Field peas: Bacterial blight, an important but sporadic disease of field peas, was common in the Wimmera during 2012. Bacteria survive on seed and pea stubbles, and are spread during wet weather by rain splash, wind-borne water droplets and plant to plant contact. Bacteria become pathogenic following crop damage caused by mechanical means, frost or severe weather conditions.

Chemicals are not effective for controlling bacterial blight. However, bacterial blight can be avoided by using an integrated approach to management that encompasses planting disease-free seed, crop rotation, avoiding early sowing and growing resistant varieties.

In 2012 some field pea varieties classified as resistant or moderately resistant had more bacterial blight damage than expected. However, these varieties generally had less bacterial blight damage compared to other commonly sown varieties. Subsequently, resistance ratings have been revised for 2013.

Early sowing of field peas can be desirable to maximise grain yield. However, early sowing can also lead to significant crop losses from ascochyta blight, as ascochyta spores are released from stubble early in the season. Fortunately, Blackspot Manager, an ascochyta blight forecasting model, can be used by growers to help identify the best balance between early sowing and potential yield loss from ascochyta.

Lentils: Ascochyta blight was detected at low levels in 2012, but failed to develop. In high disease pressure situations Nipper and Northfield varieties will require careful monitoring and the application of foliar and podding fungicide sprays may be necessary. Nugget and other MS rated varieties will require similar monitoring and spraying to protect seed pods.

Faba beans: Faba bean crops had low levels of cercospora, chocolate spot and rust early in the season, but the diseases failed to develop due to dry conditions in the spring. The use of resistant varieties is important to reduce the impact of diseases. Unfortunately, there are no disease reaction ratings available for cercospora, as resistance reactions have been variable and inconsistent.

Lupins: Phomopsis is a lupin disease which can cause the stock disease lupinosis when animals graze lupin stubbles. As phomopsis has been detected at low levels in lupin crops during the last few years, growers are reminded to check stubbles before grazing with sheep.

Vetch: Rust, ascochyta and chocolate spot did not cause as much damage in vetch, as in previous seasons. Crop protection products: There are often changes to permits for the use of fungicides in pulse crops. See Pulse Australia’s website for recent information on Crop Protection Products.

Integrated Disease Management

To reduce the risk of disease damage in 2013 growers will need to implement an integrated disease management strategy. This strategy will include sowing healthy seed, knowing the variety resistance rating, using seed dressings, paddock selection and active crop monitoring for disease to ensure the timely foliar fungicide application.

Seed quality

Testing seed for germination, vigour and seed-borne diseases before sowing is important. Seed-borne diseases can affect germination and seedling vigour, especially when conditions were favourable for disease late in the growing season. Infected seed may be smaller, shrivelled or discoloured, depending on the level of infection.

In some situations, seed infection may not be noticeable and testing needs to be carried out by specialist laboratories (see list at end of fact sheet). Commercial seed tests also identify seed lots with poor germination/vigour.

Fungicides

Seed treatments are a cheap and effective method for suppressing some diseases.

Fungicide seed treatments do not combine well with rhizobium bacteria used for inoculation. Read the labels for compatibilities. Seed should be treated with fungicide and then, in a separate operation, inoculated with rhizobium just before sowing. Sowing should occur immediately after rhizobium has been applied.

Foliar fungicides are an important part of the integrated management of pulse diseases. Although many pulse varieties are considered resistant to diseases, for example ascochyta blight in chickpeas, they may still require a foliar fungicide application at podding to reduce seed infection and prevent yield and quality loss.

See the Pulse Australia’s Information note Pulse Seed Treatments and Foliar Fungicides for more information.

Interpreting Resistance Classifications

Below is an explanation of the resistance ratings used in this guide for foliar diseases, and how they should be interpreted.

• R - Resistant, the disease will not multiply or cause any damage on this variety.
• MR - Moderately Resistant, the disease may be visible and will multiply slightly, but it will not cause significant loss. However, under severe disease pressure fungicide applications may be required.
• MS - Moderately Susceptible, the disease may cause losses up to 15 per cent or more in very severe cases.
• S - Susceptible, the disease can be severe on this variety and losses of 15-50 per cent can occur.
• VS - Very Susceptible, this variety should not be grown in areas where a disease is likely to be a problem. Losses greater than 50 per cent are possible, and the build up of inoculum will create problems for other growers.

These classifications are only a guide, and yield losses will depend on the environment and seasonal conditions. No pulse crops or varieties are immune to disease and fungicide application may be required under severe disease pressure.

Further Information

Detailed information on each of the pulse diseases can be obtained from DPI Information Notes:

• Diseases of Grains, Other Crops and Pastures
• Pulse Australia
• National Variety Trials
• Victorian Winter Crop Summary
• Seed Health Testing in Pulse Crops (AG1250)
• Pulse Seed Treatments and Foliar Fungicides
• Grain Legume Handbook. See Ch 3 Seeding
• Blackspot Management Guide for Victoria
• SARDI Faba Bean Disease Management Strategy
• Pulse Australia Lentil Disease Management Strategy
• Pulse Australia Field Pea Disease Management Strategy

Seed Testing Laboratories

• AgriFood Technology, Box 728, Werribee, Vic 3030. Tel. 03 9742 0555
• AGWEST Plant Laboratories,
• DAFWA, 3 Baron Hay Court, South Perth, WA 6151. Tel. 08 9368 3721
• AsureQuality, 3-5 Lillee Crescent (PO Box 1335) Tullamarine Vic 3043. Tel. 03 8318 9024
• SARDI Seed Testing Service, GPO Box 379, Adelaide, SA 5001. Tel. 08 8303 0360
• Seed Testing Laboratory, DPIW, Mt Pleasant, Tasmanian DPIW, 165 Westbury Road, Prospect, TAS 7250. Tel. (03) 6336 5248

Contact/Services available from DPI

DPI Field Crops Pathology, Grains Innovation Park, 110 Natimuk Rd, Horsham 3400. Tel (03) 5362 2111, or the DPI Customer Service Centre 136 186

Acknowledgements

National ratings for pulse crops are supplied by Pulse Breeding Australia (PBA) and were used in the preparation of this guide.

This guide was prepared by Frank Henry, with assistance from Helen Richardson (DPI Horsham). Financial support by the GRDC is gratefully acknowledged. Last Updated: 6th February, 2013.