This season, Sclerotinia white mould, has been found in lentil and chickpea crops in several districts throughout the Victorian Mallee. The prolonged damp conditions throughout winter have favored disease development. Other pulses, including faba beans, vetch and lupins, can also develop sclerotinia white mould.
Sclerotinia white mould is a sporadic disease that only develops under specific conditions. The disease has been known to develop in wetter seasons, although isolated reports of sclerotinia white mould at low levels every few years is not uncommon. Therefore, there is currently limited information on the effective in crop control options or expected yield losses that could be attributed to the sclerotinia white mould in pulses. However, current and future management options can be found below.
Growers and advisors are advised to inspect crops for signs of disease, and in severe cases consider the management options listed below. This includes changing crop rotations and not retaining infected seed for sowing next season.
To track the spread of sclerotinia white mould in Victoria, for a formal identification and assist our research please provide samples to:
Private Bag 260
Horsham Vic 3401
What to Look For
A small number of dead plants scattered throughout a crop are the first signs of sclerotinia white mould. Affected plants often first wilt and then rapidly die, often without turning yellow (Figures 1 and 2). When conditions favour further disease development, large patches of dying plants can be observed within an affected crop (Figure 3).
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). This usually occurs on the stems or the surface of the root. Just below ground level, small black fungal bodies called sclerotia (which are irregular in size and shape), can sometimes be seen mingled with white cottony fungal mycelium (Figure 5).
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 healthy tissue. Within a few days of infection, plants start to wither then die.
Sclerotia formed on infected plants enable the fungus to survive to the following year. 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 disease 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 Control in Victoria
The canopy closure sprays of carbendazim to manage Botyrtis Grey Mould (BGM) in lentils will not manage Sclerotinia and is an illegal off label use of a restricted use chemical. Currently, there are limited fungicides registered for the management of Sclerotinia white mould in pulse crops. Boscalid (Filian®) is currently permitted to be used to control Sclerotinia in lentil. There are a variety of products that are registered for control of other fungal diseases in crops such as lentils or chickpeas, including products containing Bixafen + Prothioconazole (Aviator® Xpro®) or Tebuconazole + Azoxystrobin (Veritas ®). Use of any of these products to control Sclerotina in pulse crops is off label, which may be allowed under the Agricultural and Veterinary Chemicals (Control of Use) Act 1992 in Victoria in certain situations.
It is critical that people using chemicals off label:
- DO NOT use a Schedule 7 Dangerous Poison (eg. Carbendazim) in an off label manner without a permit from 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.
Efficacy of chemicals used off label at this time of the year in pulses is complicated by canopy closure. Increasing the water rate may help with application and 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 Australia.
For more information on the off label use of chemical in Victoria go to http://agriculture.vic.gov.au/agriculture/farm-management/chemicals/off-label-chemical-use
Grazing, where applicable, 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.
Long term Management
Use of disease-free seed minimises the risk of disease establishment and establishment in a new area. It is important to avoid sowing susceptible crops in areas where the disease is known to be present or regularly develop.
Crop rotation is the best method of control once the disease has become established. Cereal crops are not affected by sclerotinia white mould and provide a good disease break. Pulse crops, oilseeds (canola), legume-based pastures and and some weed species, such as capeweed are all good hosts for the pathogen (Table 1). These hosts may also be present on the edge of paddocks and on roadsides.
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 which are less susceptible to sclerotinia white mould than chickpea.
Seed harvested from infected crops should not be used for sowing. No commercial seed treatments are known to control this disease in crop.
Sow within the recommended sowing window for your district. Early sown chickpea crops are more prone to developing sclerotinia white mould.
Table 1. Host range of sclerotinia white mould.
|Potential Severity of Disease on Crop||Disease Host|