While 2018 was disastrously dry for many, there may be some 'silver lining' in terms of leaf-borne fungal disease pressure - with little inoculum allowed to build-up during the dry season.
However, researchers are warning that growers need to remain vigilant, with soil-borne diseases such as rhizoctonia root rot and crown rot potentially more of a problem following dry years.
Rhizoctonia root rot and crown rot are two cereal diseases likely to pose significant risks in the southern region and southern New South Wales, where rainfall was below average last year.
In South Australia, growers are advised to be careful to not overuse cereal cyst nematode-susceptible varieties. While medium to high risk levels have increased from 2 to 4 per cent in five years, low levels were detected in 20 per cent of SA paddocks in 2018.
The lack of rainfall last year reduced the breakdown of cereal stubble in pulse and oilseed break crops, so the risk of crown rot in wheat this season following break crops is likely to be greater than normal.
Soil-borne disease experts, supported by the GRDC, advise growers to know their paddock disease risk profile well ahead of sowing by having their soils tested through PREDICTA B.
This is the DNA-based service that identifies pathogens posing the greatest threat to cereal crops. It is provided by the South Australian Research and Development Institute (SARDI), funded by GRDC.
Soil-borne disease experts, supported by the GRDC, advise growers to know their paddock disease risk profile well ahead of sowing by having their soils tested through PREDICTA B
Dr Alan McKay, the leader of SARDIs soil biology and molecular diagnostics group, says there will be a particular risk where growers opted to grow wheat-on-wheat, even if the 2018 crop failed.
I expect rhizoctonia and crown rot will be the main issues during 2019 as a result of low growing season rainfall," he says.
"Growers in SA should also keep an eye on cereal cyst nematode, as levels have been trending higher over the past five years.
Rhizoctonia, especially, has a competitive advantage in low moisture situations and its levels have almost certainly increased during 2018. It survives best when there is no summer rainfall.
"If we do experience a dry summer, crop seedlings will be exposed to high levels of rhizoctonia and the impact will be greater if the season starts late."
Rhizoctonia root rot can halve cereal yields, and barley is most susceptible.
Dr McKay says development of the PREDICTA B soil testing service for rhizoctonia had enabled pathogen levels to be effectively monitored to inform growers paddock planning.
He says testing for crown rot ahead of sowing in 2019 is strongly encouraged.
I expect rhizoctonia and crown rot will be the main issues during 2019 as a result of low growing season rainfall
SARDI research scientist Marg Evans says although crown rot requires moisture in autumn to infect the crop, a dry spring like the one experienced last year favoured expression of the disease.
The fungus grows quicker in water-stressed plants and in warm weather, and damage is more likely in intensive cereal rotations - especially in durum wheat, she says.
The characteristic white heads are symptomatic of crown rot but, given these only appear in seasons with a dry finish, the absence of white heads does not indicate freedom from crown rot.
Crown rot survives for up to four years in plant residues and stubbles, and infection occurs when plants come in close contact with infected residues.
Soil samples provided for PREDICTA B testing should include stubble.
The risk of stubble-borne diseases, such as crown rot, will be underestimated if stubble is not added to the soil sample, Dr Evans says.
Dr McKay says, on average, Australian grain growers incurred more than $200 million a year in lost production due to cereal root diseases.
By using PREDICTA B, combined with advice from an accredited agronomist, disease pathogens can be detected and managed before losses occur, he says.
More information: Dr Alan McKay, SARDI, 08 8429 2216, email@example.com