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Lupinosis risk this season

  • Ranging from Geraldton to Albany and east into central grainbelt.
Harvested lupin seed sample containing orange-yellow coloured seed infected with Phomopsis.
Harvested lupin seed sample containing orange-yellow coloured seed infected with Phomopsis. Photo courtesy of: Anonymous grower.

This season DPIRD has been notified of several cases of lupinosis in sheep following grazing of Phomopsis infected lupin stubbles, fallen harvested seed and pod trash in paddocks. The severity of cases has varied, and locations have been widespread and ranged from Geraldton to Albany, and east into the central grainbelt.

Conducive conditions for Phomopsis were experienced during pod filling and maturation in the wet spring last year.

A spike in cases were investigated by DPIRD Field Veterinary Officers and private vets in Geraldton, Northam, Kondinin, and Albany following the March 2023 rain events, which also increased fungal development.

What is Phomopsis?

Phomopsis black fruiting bodies visible on a lupin stem.
Phomopsis black fruiting bodies visible on a lupin stem. Photo courtesy of: Geoff Thomas (DPIRD).

Phomopsis stem and pod blight is caused by the fungus Diaporthe toxica.

Phomopsis on an albus lupin pod that has caused seed infection.
Phomopsis on an albus lupin pod that has caused seed infection. Photo courtesy of: Ciara Beard (DPIRD).

Pod infection can appear as a dark lesion on the surface of the pod, affecting part or all of the pod. Pod lesions can lead to fungal growth inside the pod and seed infection, causing shrivelled or discoloured light to golden brown seeds. Cotyledons inside infected seeds can remain green rather than yellow.

Pod and seed infection are more likely when there is heavy rain during the period of seed and pod maturation. These circumstances were common last season.

Diaporthe toxica lesions are not usually visible on stems or branches of green plants, the fungus will infect green plants but remains latent as microscopic structures until senescence of the plant tissue. Rain and moisture on senescing or dry lupin stems allows the fungus to grow saprophytically producing characteristic black fruiting bodies on affected stubble.

Adverse reactions caused by Phomopsis

Phomopsis stem and pod blight occasionally causes yield losses, however the major impact of infection is the production of a toxin by the fungus as it grows in mature lupin stems or in seed.

The toxin can cause sickness or death (lupinosis) in livestock if they graze on infected stubble or if feeding of infected seed is poorly managed. Infected seeds are usually discoloured, ranging from golden to dark purple-brown colour.

One of the risk factors for sheep poisoning from lupinosis is when sheep are grazed too long in stubble paddocks. Sheep should be removed from the paddock when seed levels on the ground drop below 50 kg/hectare (about 40 seeds per square metre).

As the liver is damaged by the Phomopsis toxin, affected animals may present with several clinical symptoms, including jaundice (yellowing) of mucous membranes, and neurological symptoms such as blindness, loss of normal behaviour, head pressing, or blundering into dams or fences. 

It is recommended that livestock producers report any abnormal behaviour or sickness to a DPIRD field veterinary officer, or your private veterinarian.

Further information

Guidelines for grazing stubbles or feeding of affected seed are available at the department’s Lupinosis in sheep page.

Further description of Phomopsis symptoms and management are available at the department’s Lupin foliar diseases: diagnosis and management and Diagnosing phomopsis stem and pod blight in narrow-leafed lupins pages.

For more information on lupin diseases contact Plant Pathologists Geoff Thomas, South Perth on +61 (0)8 9368 3262 or Ciara Beard, Geraldton on +61 (0)8 9956 8504.

For more lupinosis or livestock related information contact your local DPIRD field veterinary officer.

 

 

Article authors: Ciara Beard (DPIRD Geraldton) and Geoff Thomas (DPIRD South Perth).

Article input: Anna Erickson (DPIRD Narrogin) and Rod Thompson (DPIRD Northam).