PHOTO: Cox Inall Communications
“Challenging” is how New South Wales plant pathologist Dr Andrew Milgate describes the disease pressure last winter and he says the message for cereal growers this season is to be vigilant about root diseases and adopt an integrated approach to disease management.
Dr Milgate, who leads the NSW Department of Primary Industries research program into winter cereal diseases, was speaking at a recent GRDC Grains Research Update in Wagga Wagga, NSW.
He said it was critical that growers were proactive and considered crop rotations and varietal selections among other tools, to minimise losses and protect yields.
“We need an integrated strategy to tackle winter cereal diseases in southern NSW, because during years like 2015, when we have an early sowing and a wet winter, the conditions are ideal for infection and disease development,” he said.
“But we can’t rely solely on chemical control; fungicide resistance is real and it’s here.”
His disease watch-list for southern New South Wales this winter includes the following.
Septoria tritici blotch
Although septoria tritici blotch (STB) has not been common in NSW for more than a decade, its re-emergence as a significant problem in Victoria makes it a threat to early sown, high-rainfall areas of southern NSW.
“STB has a long spore-dispersal mechanism, which means ascospores released from stubble during autumn in Victoria could be blown onto and infect early wheat crops in southern NSW,” Dr Milgate said.
“While the risk of widespread infection and crop losses are low for the low-to-medium-rainfall areas, the higher-rainfall areas have conditions conducive to STB becoming re-established.”
To add to the issue, STB in Victoria and Tasmania is developing resistance to triazole fungicide.
“The levels of resistance detected by our screenings show that most fungicides will still be effective in the paddock,” Dr Milgate said.
“But to avoid further losses to efficacy growers need to use multiple strategies against this disease.
“In addition to mixing or rotation of fungicides, growers need to consider crop rotations and avoid susceptible varieties.”
Yellow leaf spot
This is still the most common wheat foliar disease in southern NSW. To avoid epidemics, do not sow susceptible varieties into stubble with high levels of inoculum.
Targeted in-crop spraying has shown results in terms of small yield improvements, under high disease pressure. However, yellow leaf spot (YLS) is difficult to control once established in crops due to its short latent period. Varieties with small improvements in resistance ratings provide better protection for growers. For example, choosing a moderately susceptible variety rather than a susceptible one will reduce disease development within a paddock.
Barley foliar disease – scald
The incidence of barley scald was higher in 2015 than previous years and there are growing concerns about virulence.
“All barley varieties should be monitored for infection, sowing barley on barley should be avoided and if infection is detected growers need to consider fungicide applications to reduce potential yield losses,” Dr Milgate said.
Root and crown diseases
Crown rot and take-all are common in the southern NSW system and seasonal conditions in 2015 favoured their build up.
“Growers need to assess the risk of severe infection this season by monitoring the build-up of inoculum in paddocks with frequent winter cereal cropping rotations,” he said.
“Pre-sowing paddock surveys in 2015 found that 80 per cent of paddocks sampled had crown rot present, while 95 per cent had take-all present.”
Dr Andrew Milgate, Wagga Wagga Agricultural Institute,
02 6938 1990,
Southern cropping region trial results 2014
Septoria tritici blotch fact sheet
National Variety Trials Online
What is missing? Identifying and managing trace element deficiencies
Help needed for herbicide resistance survey
GRDC Project Code
DAN00175, DAN00177, DAN00182, DAQ00187