WA growers have been managing sclerotinia stem rot in canola for many years. However, with lupins being susceptible and grown in close rotation to canola (which is also susceptible), growers are facing increasing disease pressure from Sclerotinia sclerotiorum across a range of crops. This is due to the increasing concentration in soil of sclerotia – hardy survival structures containing dormant pathogen – which can pose a disease risk for up to six years or more.

Concerns around sclerotinia in this cropping system had triggered investment by GRDC. However, in 2021, widespread basal infections (caused by mycelial germination of sclerotia) occurred in lupin crops in the Geraldton Port Zone and Kwinana North. The disease prevalence may have been promoted by wetter than average conditions and wet soil profiles in early winter in these locations combined with mild temperatures.

This type of infection is capable of causing significant yield losses.

The issue of basal infections was raised as a significant challenge at 2021 National Grower Network (NGN) meetings in the Geraldton port zone (Dongara Summer Sesh) and Kwinana West port zone (Badgingarra Open Meeting). This resulted in a variation on the GRDC’s current sclerotinia investment that quickly provided funding to explore responses to basal infections in order to better protect lupin crops.

That means research is now underway that targets both canopy and basal (or ground-level) infection in the field, glasshouse and laboratory, with growers being involved in these efforts. The project is due to be completed in 2025.

This research is exploring disease epidemiology to better understand how the infection processes cause yield and quality loss in lupins. The new insights can then be translated into integrated disease management strategies that allow growers to minimise losses from sclerotinia through optimal use of fungicides, rotations and cultural practices.

Research so far has found that sclerotinia can develop rapidly within lupin crops given favourable weather conditions. Yield impacts have ranged from zero to 23 per cent.

Disease risk is highest in paddocks with a history of sclerotinia, in crops with dense canopies and in response to certain weather conditions. Disease develops when vulnerable growth stages (such as flowering) coincide with wet weather and temperatures from 16˚C to 25˚C (temperatures that support canopy humidity).

It is a challenging disease to manage but a profitable response to foliar fungicide application is more likely if applied prior to widespread infection developing.

Additional key findings to date include:

• An early season break can mean the disease cycle might start earlier and last longer. Moisture and high humidity favour the disease, so dense, bulky crops and wet years are likely to be a higher risk.
• Foliar fungicide application should aim to protect main stem pods and emerging branch pods, which in WA equates to application around late flowering/early pod emergence on the main spike.
• Good coverage and penetration require using high water rates (at least 100 litres per hectare).
• If a preventive application has not been done, foliar fungicide should be considered as soon as possible after disease symptoms are observed in the canopy if the outlook is for ongoing moist and humid weather with temperatures of 16˚C to 25˚C.
• Foliar fungicides applied during crop flowering are generally not effective at reducing basal sclerotinia infection, which occurs at or below ground level.

The research is being led by the Department of Primary Industries and Regional Development (DPIRD) in collaboration with the Mingenew Irwin Group (MIG) and Centre for Crop and Disease Management (CCDM) as part of a co-investment with GRDC.

More information on findings as they occur is available on DPIRD’s website.

More information: Ciara Beard, [email protected]; Geoff Thomas, [email protected]