MODERATE to severe anthracnose, as well as phomopsis pod infection, has been found in several lupin crops near Geraldton by Department of Primary Industries and Regional Development (DPIRD) crop disease surveillance.
Anthracnose
Anthracnose is a fungal disease spread by rain-splash of spores from infected plants so the disease has spread rapidly in the recurring wet weather lately.
The disease can affect stems, flowers and pods causing bending and twisting of the infected tissue with associated pink/orange spore masses within the lesion.
DPIRD plant pathologist Ciara Beard said anthracnose was favoured by wet conditions, so the greatest risk of disease is in high-medium rainfall areas, particularly in the Geraldton port zone where blue lupins are abundant.
"A period of drier weather can delay the spread of disease, but regular rainfall events this season have been ideal for the development and spread of anthracnose," Dr Beard said.
"Infection usually arises from infected seed or from adjacent infected blue lupins which act as an ongoing reservoir of infection in higher rainfall northern areas.
"Anthracnose infection on pods can result in pod abortion, yield loss and poor seed quality caused by grain discolouration in severe situations."
The albus lupin variety Amira, rated as moderately susceptible (MS) to anthracnose, has improved resistance compared with older varieties Andromeda (susceptible ) and Kiev Mutant (very susceptible) but can still suffer infection, including on pods.
Most narrow-leafed lupin varieties are at least moderately resistant moderately susceptible to anthracnose, however infection in pods can still occur under high disease pressure.
Seed can be tested by DPIRD's seed testing and certification services for the presence and quantity of anthracnose infection.
The use of clean seed is ideal, however in some circumstances, such as resistant varieties or lower rainfall environment, low levels of seed infection can be tolerated with the use of registered seed dressing fungicide.
"In high disease situations, registered foliar fungicide sprays applied at early podding on main stems and again on first order branches, if required, reduced yield loss in previous trials conducted on albus and narrow-leafed lupins," Ms Beard said.
"The anthracnose disease needs rain to actively spread therefore application of fungicide as a protectant prior to a significant rain event is most effective.
"Currently for albus lupin there are registration permits for a range of foliar fungicides, but in narrow-leafed lupin only fungicides containing Mancozeb are registered for anthracnose."
Phomopsis
Phomopsis stem and pod blight is caused by the fungus Diaporthe toxica.
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.
DPIRD plant pathologist Geoff Thomas said pod and seed infection were more likely when there was heavy rain during the period of seed and pod maturation.
"These circumstances have been widespread this season," Mr Thomas said.
"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."
READ MORE CROPPING NEWS:
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.
In most years occasional infected seed is present in most lupin samples, however this season some affected crops may have higher than usual presence of infected seed.
