Faba bean and chickpea disease management

Take home messages

• Faba bean and chickpea crops require high levels of disease management.  Emphasis has to be placed on producing high quality grain, suitable for human consumption.
• Fungicide choice and timing of application are integral to a successful disease management program.
• Correct disease identification is important for producers to identify which pathogens are present in their crops.

Introduction

Management of diseases is an integral component to pulse production.  There still remains a number of important diseases that have the potential to cause large yield losses or reduce potential returns if left unmanaged.  Pulse producers and advisers need to be aware of the important disease constraints and take every opportunity to implement disease management strategies.

Pulses for the human consumption market, such as faba bean and chickpea, require higher levels of disease management to maximise potential returns.  It is imperative that pod infection in these crops is kept to a minimum in order to prevent seed staining and maintain seed quality.  First time producers of faba bean or chickpea need to be aware that these crops demand higher levels of regular disease monitoring compared to other pulse crops such as lupin or field pea.  But the reward of producing a human consumption quality product, which often receives a premium price, is worth the effort.

Faba Bean

The main diseases of faba bean in southern NSW and northern Victoria are ascochyta blight (caused by Ascochyta fabae), chocolate spot (caused by Botrytis fabae and Botrytis cinerea) and rust (caused by Uromyces viciae-fabae).  These fungal pathogens have the potential to reduce crop yield and seed quality.  Disease management strategies for these diseases have been developed that utilise a range of chemical and non chemical approaches; such as paddock selection, crop rotation, selection of seed for sowing, variety selection, sowing date and rate, and the strategic use of foliar fungicides.  At this point in time, producers still rely heavily on fungicides as part of a disease management strategy and success is dependent on correct disease identification, timing of product application and fungicide choice.  These management strategies are available from the Pulse Australia website (www.pulseaus.com.au).

Ascochyta blight

Ascochyta blight develops early in the growing season, especially when conditions are cool and wet for prolonged periods.  Early infection results in the development of leaf lesions. These later spread and develop into stem lesions in susceptible varieties.  This can cause premature lodging in susceptible varieties.  Later in the season, after the commencement of flowering, the disease can spread onto developing pods and cause seed staining.

Chocolate spot

Chocolate spot is favoured by warm, humid conditions for prolonged periods (four-five days).  Typically the disease develops later in the growing season as crops commence flowering and after canopy closure.  Canopy closure is an important crop growth stage and marks the point where the crop’s canopy develops from single rows within the paddock to a continual cover of canopy, which then creates a humid microclimate.  Chocolate spot has the potential to develop quickly when conditions are favourable and results in pod abortion and plant damage (through leaf infection and loss of leaf tissue).

Rust

Rust can be found from mid spring and is favoured by warm temperatures (above 20°C).  The disease can develop very quickly, requiring only six hours of leaf wetness for infection.  Rust is not usually a problem every year in southern regions, and often occurs in years with good spring rainfall and mild temperatures.

Other diseases

A number of pathogens can be found on faba bean but are considered minor and usually do not cause any yield loss.

Alternaria produces symptoms very similar to ascochyta blight, but does not produce pycnidial fruiting structures within leaf lesions.

Cercospora has been identified as a problem in South Australia and Victoria, mainly in paddocks that have a recent history of faba bean production.  Under most conditions in southern NSW and northern Victoria the disease will most likely not warrant any management.  Cercospora produces leaf lesions similar to Ascochyta, but lack pycnida.

Disease management strategy – the critical periods

There are three critical periods for monitoring faba bean crops for disease:

1^st Critical Period is five - eight weeks following emergence.   Ascochyta blight is the main target at this time and the use of foliar fungicides is aimed at reducing early establishment of the disease in crop.

2^nd Critical Period is during early flowering just prior to canopy closure.  This is the last opportunity to apply a fungicide that will penetrate into the crop canopy and protect potential infection sites from disease establishment and spread.  Chocolate spot is the target disease at this time and the prevention of this disease becoming established under the crop canopy.  In ascochyta blight susceptible varieties, a fungicide application at this time will help prevent further spread of this disease.

3^rd Critical Period is 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.

Chickpea

In southern NSW and northern Victoria the important disease constraints to chickpea production are ascochyta blight (caused by Ascochyta rabiei) and grey mould (caused by Botrytis cinerea).  Unlike northern NSW, phytophthora root rot is not a widespread production issue and has not been detected in southern chickpea producing areas.  These fungal pathogens have the potential to reduce crop yield and seed quality.  Disease management strategies for both diseases have been developed that utilise a range of chemical and non chemical approaches; such as paddock selection, crop rotation, selection of seed for sowing, variety selection, sowing date and rate, and the strategic use of fungicides (both fungicidal seed dressings and foliar fungicides).  Producers still rely heavily on fungicides and success is dependent on correct disease identification, timing of product application and fungicide choice.  These strategies are available from the Pulse Australia website (www.pulseaus.com.au).

Ascochyta blight

Ascochyta blight can become established within a chickpea crop at any crop growth stage.  In susceptible varieties the first symptoms of ascochyta blight generally appear six – eight weeks after emergence and may require a foliar fungicide application.  These crops should then be monitored closely for disease development for the duration of the growing season and sprayed when appropriate.  In more resistant varieties, fungicide applications are not generally required until the crop is closer to flowering.  Depending on the resistance rating of the variety, applications of fungicide will be required as the crop enters the flowering or podding stage.

All chickpea varieties require fungicide applications at the podding stage to protect pods from infection.  No current commercial chickpea varieties have pod resistance to ascochyta blight and are prone to seed staining if left unprotected.

Botrytis Grey Mould

Botrytis grey mould can infect chickpea at any growth stage.  Seed infected by B. cinerea can result in the development of seedling blight and a significant reduction in seedling establishment if seed for sowing is not treated with a fungicide.  Later in the growing season, losses can occur once crops reach canopy closure and conditions are humid.  Grey mould can quickly cause flower abortion, pod infections and lower stem infections; resulting in poor seed set and poor grain quality.  If the crop density is high and wet conditions are forecasted, a foliar fungicide at canopy closure can reduce disease severity.

Other diseases

There are a number of other diseases that producers should be aware of when growing chickpea.

Sclerotinia can be an occasional problem, caused by Sclerotinia sclerotiorum (the same fungus that can infect canola).  The appearance of the disease is typically sporadic and generally first appears in July when conditions are very wet.

Phoma blight is caused by one of the pathogens that cause blackspot in field pea, it develops a footrot and brown/black lesions on lower leaves and stems.  The disease tends to be most damaging in wet seasons, especially in paddocks with a recent field pea history.

Disease development and irrigation

Both faba bean and chickpea can be grown successfully under irrigation.  However, producers have to maintain vigilance for the level of disease in crops to prevent the development of an epidemic.

Irrigation will provide favourable conditions for disease to develop.  Flood irrigation increases under-canopy humidity following canopy closure and increases the opportunity for chocolate spot and botrytis grey mould to develop in faba bean and chickpea, respectively.  While overhead irrigation will not only increase canopy humidity, but also provide rain splash and leaf wetness opportunities that favour the spread of ascochyta diseases as well as chocolate spot and botrytis grey mould.

If producers are going to irrigate faba bean or chickpea crops they need to:

1. Be aware of the level of disease within the crop and which diseases are present.
2. Exercise appropriate control measures before implementing irrigation (e.g. apply the appropriate fungicide at the correct time, against the target disease).
3. Monitor the crop five – seven days after irrigation and check for disease spread.  A follow up fungicide application may be necessary.

Fungicide Selection

Producers need to be aware that the range of foliar fungicides registered for use on faba bean and chickpea can be specific against certain diseases.  Products containing mancozeb or chlorothalonil will give protection against both the ascochyta diseases and the botrytis diseases (chocolate spot and botrytis grey mould).  In contrast, products containing carbendazim are effective only against the botrytis diseases.

Please refer to the Pulse Australia disease management strategies for chickpea and for faba bean or the NSW-DPI Winter Crop Variety Sowing Guide for the latest registered fungicide products.

Contact details

Kurt Lindbeck

NSW Department of Primary Industries, Wagga Wagga Agricultural Institute

02 69 381 608

kurt.lindbeck@dpi.nsw.gov.au