Take home messages

• It is important to implement integrated disease management (IDM) strategies to reduce the threat of disease during 2025.
• Where possible, choosing more resistant varieties will reduce grain yield losses caused by disease and reduce the reliance on fungicides.
• Continue to adopt a 3- to 4-year rotation between crops of the same type to reduce inoculum build-up.
• Timely fungicide applications are essential if conditions are conducive for disease development.
• Following the ‘Fungicide Five’ strategies will reduce the risk of fungicide resistance development.

Year in review

The 2024 season relied on stored moisture and, with less rainfall through many parts of the state, resulted in low disease levels. There were still early reports of severe Ascochyta blight in lentils in high-risk situations, such as lentils in tight rotations and where prolonged leaf wetness occurred, but these were easily managed. Chocolate spot was also present in susceptible varieties in areas that received spring rainfall but was easily mitigated with fungicides. Dry conditions also restricted crop growth and biomass production, and canopy closure was not achieved in many crops, which meant non-conducive disease conditions in many crops.

Varietal resistance ratings

One of the first lines of disease defence is selecting varieties with genetic resistance. With large investments and substantial effort from pulse breeders and researchers, there is now a range of varieties available across the resistance categories for many of our major pulse diseases. However, planting the same crop in close rotation, pathogen evolution can result in ratings changes or a breakdown in resistance. At the time of article writing, the latest variety resistance ratings are not available and you are encouraged to view the latest ratings once available either through the National Variety Trials (NVT) website (https://nvt.grdc.com.au/nvt-disease-ratings) or when the 2025 Agriculture Victoria Pulse Disease Guide is released on apple books or the website (https://agriculture.vic.gov.au/biosecurity/plant-diseases/grain-pulses-and-cereal-diseases/pulse-disease-guide).

Sclerotinia white mould (SWM)

Sclerotinia white mould (SWM) poses an increasing threat in southern Australian grain-growing regions. It is a damaging disease that can infect all pulse crops including lentil, chickpea, faba bean, vetch, field pea and lupin. It can also affect canola, pasture legumes and many broadleaf weeds. This disease poses its greatest risk during seasons with prolonged damp conditions.

Sclerotinia white mould is caused by the soilborne fungi, Sclerotinia spp., and produces durable survival structures (sclerotia) that survive in the soil for many years, creating a legacy effect for future pulse or canola crops. High sclerotia populations can lead to basal stem infection and seedling death. Symptoms include bleaching or cottony white fungal growth on and in foliage, stems, flowers, pods and grain. Sclerotia on/in plant foliage can contaminate harvested grain, acting as a future inoculum source if the grain is not screened. Refer to the Field Crops Diseases article ‘Sclerotinia in Victorian pulses' for images of symptoms (link given below in the section ‘useful resources’).

Field experiments have been conducted in SA, VIC, and NSW during 2023 and 2024, but dry spring conditions did not result in substantial SWM infection, highlighting the importance of environmental conditions in the development of SWM. Further highlighting the effect of season, NSWDPI experiments have shown season driven inoculum production (Table 1), with greater inoculum carry over following wet springs compared to dry springs. Management of SWM through fungicides has been highly variable on disease severity, grain yield and the subsequent inoculum levels in a paddock. The greatest driver of inoculum levels has been crop choice and spring rainfall (Table 1).

Table 1: Comparison of the weight of sclerotia produced by Sclerotinia sclerotiorum following infection of various pulse crop species grown at Wagga Wagga NSW.

Management of SWM in pulses

Currently, crop rotation and careful paddock selection to avoid SWM infection are the most effective control measures. High risk paddocks are those with canola or pulses in the rotation, a history of previous outbreaks of Sclerotinia, and/or where high growing season rainfall is forecast. There are multiple hosts of SWM, including pasture and broadleaf weed species. PREDICTA^®B testing of Sclerotinia spp. inoculum levels in soil post-harvest can assist growers in determining disease risk for the next season. The behaviour of SWM in pulses is very different from that in canola and should be managed accordingly. For example, the plant-to-plant spread of the disease is unique to lentil. We are expecting that the GRDC investment (DPI2206-023RTX) in SWM will provide more management options in the next few years.

Faba bean Ascochyta blight

Ascochyta blight in faba beans is often thought to be a substantial limitation. It can be controlled with good integrated disease management and agronomy, including crop rotation, variety resistance, mixing and rotating fungicide groups, and strategic fungicide applications. Two experiments were conducted on irrigation in Victoria to determine the relationship between disease severity and grain yield in a susceptible variety. There was no correlation between disease severity and grain yield losses during 2023, even with maximum disease severity of 20%. During 2024, a preliminary regression analysis showed a 1t/ha yield loss (a reduction from 5t/ha to 4t/ha) with 26% disease severity (P<0.05), compared to plants without disease. A 200-grain weight regression analysis also indicated a 15g grain weight loss (129.5 to 113.9g per 200 grains) with 26% disease severity (P<0.05), compared to disease-unaffected faba bean. The maximum disease severities in both years were achieved with multiple inoculation through stubble and spores and substantial irrigation. This highlights that, although Ascochyta blight on its own can cause yield loss, it is more likely to pose a greater threat in aiding Botrytis infection later in the season. This is likely through providing dead bean leaf tissue on which Botrytis can thrive.

Botrytis disease management

Botrytis affects most pulse crops (faba bean, lentil, vetch, chickpea and lupin). The disease is called chocolate spot in faba bean and sometimes in vetch. It is caused by two pathogens, Botrytis cinerea and B. fabae, which are both found across faba bean, lentil, vetch and lupin, with chickpea only affected by B. cinerea. Therefore, Botrytis can spread readily between susceptible pulse crops or from previously infected stubbles. The pathogens are necrotrophic fungi, which means they kill plant cells and then feed off those dead cells. This infection process places stress on the plant, which makes plants more susceptible to further infection. Thus, it can become more difficult to control the disease once it is established, resulting in greater disease severity.

The results from previous experiments reported in GRDC Update papers over the last few seasons support controlling Botrytis disease early in the season and minimising disease severity in the crop. An application of a dual mode of action fungicide at canopy closure should provide 1–2 months of protection, depending on environmental factors. This should protect the crop until spring when we should have a greater understanding of the future disease risk and can determine if further fungicide sprays are required. An investment (DJP2304-004RTX) into Botrytis grey mould led by Agriculture Victoria in collaboration with SARDI, FAR Australia, Trengove Consulting and NSWDPI will provide more IDM strategies and some recommendations on contributing environmental factors.

Chickpea Ascochyta blight

Chickpea Ascochyta blight is the greatest disease threat to chickpea production, with all current varieties rated moderately susceptible to susceptible. Previous Agriculture Victoria research has shown that there are differences in gross margin between fungicide strategies, but the threat of fungicide resistance means growers should adhere to product rotation. Newer, dual active chemistries provide longer protection, but the traditional multisite chlorothalonil still provides protection, just with more applications. There are new varieties in the pipeline that will have improved resistance compared to current varieties and, in preparation of their release, studies have commenced to determine how much less disease management is required with these new varieties compared to current practices.

Sowing time has also been investigated, demonstrating that sowing in early May results in significantly greater disease severity (P<0.05) compared to sowing in early July across multiple seasons. Results were variable. During 2022, there was no difference between sowing time or disease control, with an average yield of 1.38t/ha. During 2023, sowing in July resulted in 1.12t/ha decreased yield, from 3.67t/ha to 2.54t/ha, compared to May sowing. However, significant grain yield losses (P<0.05) due to Ascochyta blight were only measured in the May sown plots, with 0.49t/ha loss measured. During 2024, there was no difference in grain yield between the May and July sown full control treatments, with average grain yields of 1.18t/ha to 1.27t/ha. However, the May sown/no disease control plots only had a 1.00t/ha grain yield, significantly lower (P<0.05) than the other treatments. This highlights the importance of sowing chickpeas later than other crops in the sowing window to reduce disease control costs to prevent grain yield losses.

Fungicide withholding periods

To protect pulses, there are several fungicides available, and these vary in efficacy and label use patterns. When selecting products, it is important to consider products within an IDM program, the potential of the disease-causing pathogen to develop fungicide resistance, and the overall crop profitability. Remember that withholding periods of these products differ and following label directions is essential to remain within the maximum residue limits (MRLs). Extensive testing has been undertaken to develop these limits and use patterns. Current registrations and labels can be found on the manufacturers' websites or at the APVMA (Public Chemical Registration Information System Search – https://portal.apvma.gov.au).

Soilborne disease

There is an increased prevalence of soilborne diseases due to increased pulse cropping, and grower reports of poor crop performance indicate it may be a limitation to high pulse production and quality. GRDC’s investment in a national project led by SARDI (UOA2206-007RTX) builds upon previous research (SAGIT S218 and GRDC DJP1907-002RMX) to determine potential impacts of root diseases affecting yield and biomass and avoid major production loss and loss of export markets. Pathogens such as Fusarium, Phytophthora,and Rhizoctonia were assessed in field and glasshouse environments to quantify the impact on pulse root health, biomass production, and yield.

Results in 2024 from research conducted in Victoria on Fusarium spp. showed similar trends to 2023, where Fusarium avenaceum treatments were the most pathogenic on faba bean and lentil, producing the lowest plant establishment (60% loss), greatest plot loss percentage (18%), highest visual root disease scores (3.5/6), greatest biomass losses (58%) and highest yield losses (55%) compared to other Fusarium spp. treatments. Comparatively, F. redolens and F. oxysporum treatments were the least pathogenic. An IDM trial was also established in 2024 to test various seed treatments on F. avenaceum-infested lentil and faba bean. All fungicide seed treatments produced varying results across all assessments, producing higher plant establishment (plants/m²) than the inoculated control treatment (no fungicidal seed treatment). However, statistical significance  (P>0.05) was not observed between treatments for biomass and grain yield.

Fungicide resistance

Resistance to fungicides is becoming an increasing threat to crops across Australia. Currently, there are no new detections of fungicide resistance in pulses within Australia. Samples have been collected and tested across the Southern region, which suggests that a change in resistance is not occurring, but the threat is always present.

Pulse production is reliant on foliar fungicides and many crops have only single active fungicide products applied at multiple times throughout the season. Therefore, there is a high probability that we may observe fungicide resistance in the future if growers do not take preventative steps at present.

There are five strategies that growers can adopt to slow the development of resistance in pathogen populations and therefore, extend the longevity of the limited range of fungicides available.

• Avoid susceptible crop varieties. Where possible, select the most resistant varieties suitable and/or avoid putting susceptible varieties in high-risk paddocks.
• Rotate crops. Avoid planting crops back into their own stubble or adjacent to their own stubble.
• Use non-chemical control methods to reduce disease pressure. Delaying sowing and early grazing are examples of strategies that can reduce disease pressure.
• Spray only if necessary and apply strategically. Avoid prophylactic spraying and spray before the disease gets out of control.
• Rotate and mix fungicides/modes of action. Use fungicide mixtures formulated with more than one mode of action, do not use the same active ingredient more than once within a season, and always adhere to label recommendations.

For more information on the management of fungicide resistance, consult the ‘Fungicide Resistance Management Guide’ available from the Australian Fungicide Resistance Extension Network (AFREN) (https://afren.com.au/resources/#management-guide).

Conclusion

With unpredictable seasonal conditions each year, it is important to adopt an IDM strategy to reduce grain yield losses across all pulse diseases. This strategy should be planned early and incorporate varietal resistance, paddock rotations, reliable agronomy practices (sowing time, interrow sowing, and nutrition), mixing and rotating fungicide groups, and strategic fungicide applications. Without a solid strategy, grain yield losses of greater than 90% may be experienced, depending on the disease, if conducive disease conditions occur.

Acknowledgements

The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the authors would like to thank them for their continued support. Appreciation is given to all the organisations listed above, their staff, and the growers and agronomists who have assisted with these research programs.

Useful resources

Pulse disease guide (https://agriculture.vic.gov.au/biosecurity/plant-diseases/grain-pulses-and-cereal-diseases/pulse-disease-guide)

Victorian and Tasmanian crop sowing guide (https://grdc.com.au/resources-and-publications/all-publications/nvt-crop-sowing-guides/vic-tas-crop-sowing-guide)

CropSafe program (https://agriculture.vic.gov.au/crops-and-horticulture/grains-pulses-and-cereals/cropsafe-program) (for submission of plant samples for diagnosis, or email crop.safe@agriculture.vic.gov.au)

Diagnostic services (Crop Health Services, for example, seed testing) (https://agriculture.vic.gov.au/support-and-resources/services/diagnostic-services#h2-1)

(can also phone 03 9032 7515 or email chs.reception@agriculture.vic.gov.au)

Sclerotinia in Victorian pulses (https://extensionaus.com.au/FieldCropDiseasesVic/sclerotinia-in-victorian-pulses/)

Australian Pesticides and Veterinary Medicines Authority (APVMA) (www.apvma.gov.au) (to view crop protection product details, including minor use permits)

DPI2206-023RTX Managing sclerotinia in oilseed and pulse crops in Northern and Southern farming systemhttps://grdc.com.au/grdc-investments/investments/investment?code=DPI2206-023RTX

Contact details

Chloe Findlay
Agriculture Victoria
110 Natimuk Road, Horsham VIC 3400
0439 114 931
chloe.x.findlay@agriculture.vic.gov.au

Josh Fanning
Agriculture Victoria
110 Natimuk Road, Horsham VIC 3400
0419 272 075
joshua.fanning@agriculture.vic.gov.au
@FanningJosh_