RHIZOCTONIA bare patches are being observed in several crop types in the Albany, Geraldton, Kwinana East and Kwinana West port zones by agronomists, growers and staff from the Department of Primary Industries and Regional Development (DPIRD).
In particular, rhizoctonia root rot has been observed in many lupin and wheat paddocks, plus rhizoctonia hypocotyl rot in lupin, in the Geraldton port zone.
Rhizoctonia was also found in barley, wheat and oats near Berkshire Valley, Bindi Bindi, Carnamah, Corrigin, Kellerberrin, Holt Rock, Merredin, Narembeen, Wubin, and York.
DPIRD research scientist Daniel Huberli said in the paddock growers should look for severely stunted plants that occur in patches.
"There is usually a distinct edge between diseased and healthy plants," Dr Huberli said.
"Roots of affected plants are short with characteristic pinched ends known as spear tips.
"Distinct patches are often evident when the primary roots of plants are infected early, while infection of the crown roots later in the season may cause an uneven crop."
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Root and hypocotyl diseases can be significant problems in lupin crops, reducing stand density, plant vigour and yield.
Above ground symptoms such as poor emergence, patches in crops, uneven and stunted growth, yellowing of plants and wilting or death under water stress, particularly at flowering and grain fill, can indicate the presence of root disorders.
Below ground diseases that infect lupins include Pleiochaeta root rot, Rhizoctonia bare patch, Eradu patch, Rhizoctonia hypocotyl rot and Pythium root rot.
Dr Huberli said it was important to be aware that patches are not unique to rhizoctonia and there are other diseases which can cause them.
"In particular, patches caused by rhizoctonia or RLN are difficult to distinguish without close inspection of the plant roots and often require further laboratory tests to isolate rhizoctonia or extract any nematodes," he said.
There is nothing that can be done in season to control root diseases and while an application of nitrogen post-sowing may aid recovery, it does not prevent root damage.
Before the next crop is sown, it is important the disease or issue causing the patches in a paddock is confirmed in order to put the right management plan in place for 2023.
"For diagnosis of root disease or nematode problems in-crop, carefully dig up symptomatic plants from the edge of the patch, not the centre, as well as healthy plants from outside the patches," Dr Huberli said.
Keeping disease inoculum levels at low levels is the most effective way to minimise crop losses from root diseases.
This can be achieved by thinking long-term and implementing management
practices over more than one cropping season.
"If you have confirmed your paddock has rhizoctonia with large amounts of the crop affected this year, the best option would be to place the paddock into a grass-free break crop in 2023, such as canola, pulse or pasture," Dr Huberli said.
"Canola has been shown to reduce the level of disease in the following cereal crop, but will become a problem again in the second year of cereals."
