Sclerotinia white mould (SWM) is a damaging disease that can infect many pulse crops including lentil, chickpea, faba bean, vetch, and lupin. It can also affect canola, pasture legumes, and many weeds. This disease poses its greatest risk during seasons with prolonged damp conditions.

During 2020, seasonal conditions are appearing to be similar to those in 2019, where SWM was observed in lentil and chickpea crops throughout the Wimmera and Mallee districts in Victoria. Although it was only reported in chickpea and lentil during 2019, keep in mind sclerotinia white mould can infect other pulse crops (e.g. faba bean, vetch, and lupin).

Sclerotinia white mould is a sporadic disease that only develops under specific conditions. It requires wetter seasons to develop to damaging levels. Being a sporadic disease there is currently limited information on effective in crop control options or expected yield losses that it causes.

What to look for

A small number of dead plants scattered throughout a crop are the first signs of SWM. Affected plants often wilt then rapidly die, often without turning yellow (Figures 1 and 2).

When conditions favor further disease development, large patches of dying plants can be observed within an affected crop (Figure 3).

The stems of plants within affected areas develop a slimy soft rot from which droplets of a brown liquid may exude. Infected tissues then dry out and may become covered with a web of white mycelium of the fungus (Figure 4). Just below ground level, small black fungal bodies call sclerotia (which are irregular in size and shape) can sometimes be seen mingled with white cottony fungal mycelium (Figure 5).

Disease Cycle

Sclerotinia white mould, caused by Sclerotinia sclerotiorum, S. minor and S. trifoliorum, is usually established from sclerotia (survival bodies of the fungus) present in the soil or introduced with contaminated seed. Outbreaks are more common when very wet conditions occur in late June and early July.

The sclerotia germinate in moist soil and either directly infect roots via mycelium or produce air-borne spores which infect the above ground parts of the plant. Once established, the fungus rapidly moves to adjacent healthier tissue. Within a few days of infection, plants start to wither then die.

Sclerotia (survival bodies) formed on infected plants enable the fungus to survive several years. Individual seeds can be contaminated with the fungus and/or sclerotia may be present in the seed sample. Sclerotia can remain viable in the soil for up to eight years.

Soil-borne sclerotia are the most important infection source for establishing disease in following crops and seasons. Seeds infected with Sclerotinia can be the cause of disease establishment in otherwise Sclerotinia-free areas.

Current controls in Victoria

Currently, there are limited fungicides registered for the management of sclerotinia white mould in pulse crops. The canopy closure sprays of carbendazim to manage Botrytis Grey Mould (BGM) in lentils will not manage SWM and is an illegal off label use of a restricted use chemical.

Grazing, where applicable (i.e. vetch), may open the canopy and allow better coverage of the fungicide and therefore, increase fungicide efficacy. Consider cutting hay earlier to prevent a decrease in hay quality.

Fungicides

The following tables summarise products that may be considered for use to control SWM. Please note that there is a high level of risk associated with the off-label use of agricultural chemicals. These risks should be assessed prior to using chemicals off-label.

Chemical use post canopy closure in pulses is complicated by reduced efficacy. Increasing the water rate may help with coverage but penetration into the crop canopy may be limited. Currently, there are no results on the efficacy or benefit of the application of fungicides to control sclerotinia white mould in pulses in Australia.

Use of products to control SWM where it is not registered or under permit is off-label, which may be allowed under the Victorian Agricultural and Veterinary Chemicals (Control of Use) Act 1992 in certain situations.

Table 1 shows chemicals which are registered or under permit to control SWM in the listed pulse crops. Use in Victoria according to the permits would be considered off-label as the permits are not applicable to Victoria.

Table 2 shows fungicides /fungicide actives which are registered for control of Sclerotinia in canola and for use on other diseases within the stated pulse crops, they may provide incidental control of SWM in pulse crops. However, efficacy against SWM in situations not addressed by the label or permits has not been assessed and may prove to be ineffective. For further information contact the product manufacturer or your local agronomic advisor.

Table 3 highlights products which are registered for control of Sclerotinia in canola but are not registered for use in pulses. Their use on Victorian pulse crops is off label and subject to the conditions outlined below.

Table 1. Fungicides that are registered or permitted in the listed pulse crops for control of sclerotinia white mould

Fungicide Active	Trade name, example	Registered crop	Disease
Boscalid	Filan Fungicide®	Lentil (A) Lupin (B)	Sclerotinia Sclerotinia
Azoxystrobin	Amistar 250SC Fungicide®	Beans	Sclerotinia

(A) APVMA Minor use permit - PER82476, expires 30/09/2022
(B) APVMA Minor use permit - PER82240, expires 30/09/2020

 

Table 2. Fungicides that are registered for use in pulse crops to control the listed diseases on the label and are registered for control of sclerotinia stem rot control in canola

Although these fungicides may provide incidental control in pulse crops, they have no label registration or permits for control of sclerotinia white mould in pulse crops. Therefore, the efficacy on sclerotinia white mould in pulse crops has not been assessed and they may prove ineffective and the use would be off-label.

Fungicide Active	Trade name, example	Pulse Crop Registered	Disease
Bixafen + Prothioconazole	Aviator Xpro Foliar Fungicide®	Chickpea Lentil Faba bean Canola	Ascochyta Ascochyta, Botrytis, Chocolate spot, Rust Ascochyta, Cercospora, Chocolate spot Sclerotinia
Tebuconazole + Azoxystrobin	Veritas Fungicide®	Chickpea Lentil Faba bean Vetch Lupins Canola	Ascochyta Ascochyta, Botrytis, Chocolate spot, Rust Ascochyta, Cercospora Botrytis Botrytis Sclerotinia

Table 3. Fungicides which are registered for control of sclerotinia in canola but are not registered for use in pulses

The use of these fungicides in Victorian pulse crops is off-label and subject to off-label conditions.

Fungicide Active	Trade name, example	Pulse Crop Registered	Disease
Prothioconazole + Tebuconazole	Prosaro 420 SC Foliar Fungicide® Titan Prothioconazole & Tebuconazole Fungicide Smart Pro Grow 420 SC Fungicide Conquest MantaRay 420 Fungicide	Not registered in pulses Not registered in pulses Canola Canola	None None Sclerotinia Sclerotinia

Victorian chemical off-label use requirements.

It is critical that people using chemicals off-label:

• DO NOT use a Schedule 7 Dangerous Poison (eg. carbendazim and procymidone) in an off-label manner without the permit of the Australian Pesticides and Veterinary Medicines Authority (APVMA)
• DO NOT use the chemical at an above label rate
• DO NOT use the chemical more frequently than the label states
• DO NOT use the chemical contrary to any prohibitive label statements (eg. DO NOT statements)

Any person that uses a chemical off-label must accept and manage all risks associated with that use, such as the risk of residues in produce or the environment, occupation health and safety concerns, and the efficacy of the chemical. This is particularly important for export commodities as in the past access to these markets has been disrupted due to unacceptable residues caused by off-label use.

For more information on the off label use of chemicals in Victoria.

Long term management

Crop rotation provides the most effective strategy for reducing the levels of SWM in a paddock. Cereal crops are not affected by SWM and provide a good disease break. Pulse crops, oilseeds (canola), legume-based pastures, and some weed species, such a capeweed are all good hosts for the pathogen (Table 4). These hosts may also be present on the edge of paddocks and on roadsides.

Table 4. Host range of sclerotinia white mould

Crop type	Potential severity of disease	Disease host
Wheat	None	No
Barley	None	No
Oats	None	No
Canola	Moderate - Severe	Yes
Safflower	Moderate	Yes
Sunflower	Severe	Yes
Linola	Moderate	Yes
Field pea	Minor	Yes
Chickpea	Moderate - Severe	Yes
Faba bean	Minor	Yes
Lupin	Moderate - Severe	Yes
Lentil	Moderate	Yes
Vetch	Minor	Yes
Legume pasture	Minor	Yes

If a sclerotinia white mould problem does occur, a four-year break from disease hosts is required to substantially reduce the number of sclerotia in the soil. The most practical option is to use cereals and other legumes that are less susceptible to sclerotinia white mould than chickpea and lentil.

Seed harvested from infected crops should not be used for sowing. No commercial seed treatments are known to control this disease in crops. Sowing disease-free seed will help to prevent sclerotinia white mould from establishing in disease-free paddocks.

Sow within the recommended sowing window for your district. Early sown chickpea crops are more prone to developing sclerotinia white mould.

Tracking sclerotinia

To track the spread of sclerotinia white mould in Victoria, for a formal identification and to assist our research please provide samples to:

Joshua Fanning                                                                                                                                        Agriculture Victoria                                                                                                                                      Private Bag 260                                                                                                                                        Horsham, Victoria, 3401

Further information links

Identification and Management of Field Crop Diseases in Victoria – Sclerotinia Rot of Chickpea

Identification and Management of Field Crop Diseases in Victoria – Sclerotinia Stem Rot of Canola

Agriculture Victoria – Off-label chemical use

Acknowledgments

Thank you to Gordon Cumming (GRDC, Chemical Regulation Manager), Grant Hollaway (Agriculture Victoria, Senior Research Scientist – Field Crop Pathology), and Maresa Heath (Agriculture Victoria, Project Officer – Plant Residues) for their contributions and expertise.

 

The authors wish to acknowledge the funding provided by GRDC that allows this work to occur. This information has been generated by the GRDC funded project DJP1097-001RTX.