Australian Pulse Bulletin

Faba bean fungicide guide: 2020 season 

Foliar fungicide applications will help in the management of faba bean diseases. There are four main fungal diseases of faba and broad bean that require monitoring, Chocolate spot (Botrytis fabae and B. cinerea), Ascochyta blight (Ascochyta fabae), Cercospora leaf spot (Cercospora zonata) and Rust (Uromyces vicia-fabae). 

Decisions need to be made such as when to start the fungicide application program and how often to spray, depending on the varietal resistance, the prevailing weather conditions and the potential yield of the crop.

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 first fungicide application must be applied as early as necessary to minimise the establishment of the disease. Additional applications are required if the weather conditions favour disease development and spread. Be aware of the critical spray application times as part of an overall fungicide program. This includes:

1st critical period – 4–6 weeks after emergence.

2nd critical period – during early flowering just before canopy closure. This is the last opportunity to apply fungicides that will penetrate into the crop canopy and protect potential infection sites from disease establishment and spread. Follow up fungicide applications may be needed if weather conditions are conducive to disease development.

3rd critical period – at the end of flowering and early pod fill. Applications of fungicide at this time should be aimed at protecting developing pods and preventing any further disease spread. The target diseases at this time are ascochyta blight, chocolate spot and rust. An insecticide might also be required during this period.

Disease monitoring should be started after crop emergence (4 – 6 weeks after emergence) as cercospora leaf spot and ascochyta blight can develop in crops in the early stages. If disease takes hold it can be very difficult to recover crops, as the fungicides have no curative action. Protective fungicide applications may be needed in longer growing seasons until the end of podding. Fungicides remain effective for approximately 10-14 days. Keep in mind that all new growth after fungicide application is unprotected. 

Timing of fungicide application is critical. These diseases can spread rapidly, so DO NOT DELAY application. An application in advance of a rain front period is desirable for maintaining yield expectations. Delaying application until after a rain front will have much reduced efficacy. Current research shows the value of spraying prior to rain.

The need for repeated fungicide applications depends on the growth stage of the crop, the time since the last fungicide application and the likelihood of further conditions favouring disease development. Unprotected crops can lose over 50% in yield due to diseases such as chocolate spot. The numbers of applications per crop is limited for some products to minimise the development of fungicide resistance and manage residue limits. Check the labels for maximum number of applications permitted. In high disease risk seasons, where multiple fungicide applications are required, alternate products with different active ingredients.

Pulse Australia can apply for Minor Use Permits when required to help growers manage disease in faba bean crops along with all the currently registered products.

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: 

• Faba bean: Integrated disease management
• CropPro faba bean disease manual
• Fungicide resistance in grain crops (including pulses)

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  Cercospora (SARDI)

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  Mouldy pods caused by chocolate spot

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  Early indications of chocolate spot

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  Chocolate spot on faba bean leaves and flowers (J Davidson).

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  Ascochyta blight on faba bean leaves (J Davidson).

Fungicide Minor Use Permits for faba bean 20

Many Minor Use Permits have short term expiry dates (e.g. 30/11/2019) 

Fungicides registered for use for faba bean

Faba Bean Foliar Fungicide	Trade Name example	Chocolate Spot	Rust	Ascochyta	Cercospora	WHP Harvest
Chlorothalonil 720	CC Barrack 720	1.4 to 2.3 L/ha	1.4 to 2.3 L/ha	NR	NR	7 days
Mancozeb 750	Dithane DF	1.0 to 2.2 kg/ha	1.7 to 2.2 kg/ha	1.7 to 2.2 kg/ha	1.7 to 2.2 kg/ha	28 days
Carbendazim	Spin Flo	500 mL/ha	NR	NR	NR	28 days
Procymidone 500	Sumislex 500	500 mL/ha	NR	NR	NR	9 days
Copper	Champ 500DF	1.2 kg/ha	1.2 kg/ha	NR	NR	1 day
Metiram 700	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
Prothioconazole + Bixafen	Aviator XPro	600 mL/ha	600 mL/ha	400 to 600 mL/ha	400 to 600 mL/ha	N/A
Azoxystrobolin + Tebuconazole	Veritas	0.75 to 1.0 L/ha	300 mL/ha	0.75 to 1.0 L/ha	300 mL/ha	28 days

NR = Not Registered (not effective for this disease)  

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