Australian Pulse Bulletin

Field pea fungicide guide: 2020 season

Fungicide applications will help control some field pea diseases. There are three main fungus diseases in field peas that require monitoring: Black Spot Complex (Ascochyta), Powdery mildew (PM) and Downy mildew (DM). 

Pulse Australia have Minor Use Permits from APVMA when required, to help growers manage disease in field pea crops.

Fungal disease control is based on the use of integrated disease management to minimise the injury to crops from plant pathogens. Efficient use of foliar fungicides is based upon the protection of plants rather than curing existing infections. The application of foliar fungicides to manage ascochyta blight have generally proven to be uneconomic for field pea yields less than 2t/ha. If yield potential is greater than 2t/ha then apply a foliar fungicide at 9 nodes prior to a significant rain front. If ascochyta blight disease is present then follow up again at early flowering, again prior to a significant rain front. Fungicide can be applied when disease lesions are expanding on lower leaves before canopy closure, but can be earlier if the disease appears early.

Downy mildew may develop in years with long periods of cold, wet conditions in winter. The disease can take hold of establishing seedlings and result in reduced plant populations. Seed treatment of metalaxyl (Apron®, Rampart®, Axiom®, Mantle®) is highly effective on downy mildew, and is the first priority control option to choose where the risk is high. It does not control ascochyta blight. A foliar application of chlorothalonil may be effective in suppressing the downy mildew in a salvage operation if detected in the seedling stage, but this is less effective than a seed dressing because the damage has been done earlier. The foliar fungicides containing phosphorous acid or metalaxyl are not registered in peas.

Mild days and cool nights (that favour dew formation) late in the season can favour development of powdery mildew. Powdery mildew can spread very quickly under ideal conditions. Seed treatment is not effective against powdery mildew. A foliar application of tebuconazole (eg Folicur®, various Tebuconazole’s) can be effective in suppressing powdery mildew if applied as soon as it is first detected. Triadimefon products (eg Accord®, Triad®, various Triadimefon’s) can be effective in suppressing the powdery mildew, but a repeat application may be needed.

Timing of fungicide applications is critical. An application in advance of a rain front provides maximum protection. Delaying application until after a rain front reduces efficacy significantly, as rainfall will rapidly promote spread of inoculum. Close monitoring for early symptoms will give greater opportunities to minimise disease establishment and spread.

Both chlorothanonil and mancozeb are both persistent and rain-fast chemicals.

Keep in mind that all new growth after spraying is unprotected, and new leaves will appear in 4-6 days in winter, but only 2-3 days in spring as conditions warm up. 

Seasonal Conditions in 2020

Seasonal conditions have changed markedly in 2020 compared to the last few seasons, especially in the eastern states. After a hot and dry summer in many regions, with bush fires threatening many farming communities, early February and March saw widespread rain events across much of the eastern states coming from north west cloud bands. NSW and Victoria were well above average for this period and meant that dry soils were all recharged ready for the winter cropping seasons. Follow up rain has got the season off to an excellent start. Qld also received reasonable falls in February, but many areas have not had decent follow up falls, so crops are struggling at present. South Australia has had some reasonable rainfall, the south eastern areas were too wet and crop planting was delayed. Overall through SA has crops off to a good start.  In Western Australia the southern and eastern grain belts have again had a dry start, similar to 2019, but recent rainfall has improved prospects. 

These conditions have meant that diseases need to be monitored closely in many regions, particularly in the eastern states. Monitoring needs to be continued through the different growth stages of the crop. With good access for ground sprayers this year, allowing for high water rates and canopy penetration, timely fungicide application will give the crop the best chance of a high yield. 

For more detailed information on disease management: 

• Field pea best management guide
• CropPro field pea disease manual
• Fungicide resistance in grain crops (including pulses)

Fungicides registered for disease control in field peas

Field pea Foliar Fungicide	Trade Name example	Ascochyta blight	Botrytis grey mould	Powdery mildew	Downy mildew	WHP Harvest
Chlorothalonil 720	CC Barrack 720	NR	NR	NR	1.1 to 1.8 L/ha Qld, Tas, WA only	7 days
Mancozeb 750	Dithane DF	1.7 to 2.5 kg/ha	NR	NR	NR	14 days
Azoxystrobolin + Tebuconazole	Veritas	NR	0.75 to 1.0 L/ha	NR	NR	28 days
Metiram700	Polyram DF	1.0 to 2.2 kg/ha	1.0 to 2.2 kg/ha	1.0 to 2.2 kg/ha	1.0 to 2.2 kg/ha	42 days
Triadimefon 125	Genfarm Triadimefon	NR	NR	500 mL/ha NSW, Vic, Tas only	NR	14 days
Zineb 800	Barmac Zineb	NR	NR	NR	125 g/ha	7 days
Copper Oxychloride	Champ 500DF	2.5 kg/ha	NR	NR	NR	1 day
Tebuconazole	Folicur SC	NR	NR	145 mL/ha	NR	3 days
Prothioconazole + Bixafen	Aviator XPro	400 to 600 g/ha	NR	NR	NR	N/A

Many of the Minor Use Permits have short term expiry dates (e.g. 30/11/2017) 

NR = Not Registered 

Read the Label As with any chemical application, care should be taken to observe all the label conditions for each product. Some label advice is different for each state or region, so for best results, it is important that this is followed. Many of our pulse crops are exported for human consumption, so market access is dependent on having the product free of chemical residues. Australian has a reputation for providing clean and safe produce so it is vital that this is maintained by using chemicals according to regulations. All permits have label recommendations for use rate and withholding periods (WHP) that must be observed so grain will comply with Maximum Residue Limits (MRL) allowable for market access.

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Last updated: 13 August 2020