Phomopsis lesions detected in Great Southern lupins

The crop was at leaf drop and the lesions were evident on the stems.

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

The toxin can cause livestock sickness or death - lupinosis - if they graze on infected stubble or if they are fed infected seed.

Department of Primary Industries and Regional Development plant pathologist Ciara Beard said Phomopsis stem lesions WERE not usually visible on green plants.

"The fungus will infect green plants but remains latent as microscopic structures until senescence of the plant tissue," Dr Beard said.

"Rain and moisture on senescing or dry lupin stems allow the fungus to grow saprophytically producing characteristic black fruiting bodies on affected stubble.

"Chemical desiccation or plants suffering a period of premature moisture stress can lead to rapid expression of stem symptoms as plants senesce."

The fungus is present in all lupin growing regions and every year virtually all lupin crops in WA will be infected to some degree, however most varieties are moderately resistant or better and are low risk.

Lupin varieties such as Coyote, Jenabillup and Quilinock are more susceptible to infection in stems and pose a greater risk of lupinosis for grazing animals, particularly after summer rainfall.

Varieties such as Mandelup and Quilinock have greatest risk of infected pods and seed.

Phomopsis infection had previously been reported in the Geraldton region back in September.