Pathogen burden in NSW winter cereal cropping

Pathogen burden in NSW winter cereal cropping is increasing

Cropping
Competition winning crop of dryland wheat in the Riverina. Photo: Tom Dwyer

Competition winning crop of dryland wheat in the Riverina. Photo: Tom Dwyer

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Rotations to reduce pathogen burden and disease update for 2020 - Andrew Milgate (NSW DPI)

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Disease burden in southern winter cereal crops is increasing as consecutive cropping is building pathogen loads according to a survey conducted by NSW DPI officers Andrew Milgate and Steven Simpfendorfer across the northern region.

The results from that survey formed the address which Mr Milgate presented to the GRDC Grains Research Update webinar on diseases in winter cereal crops.

"We really need to consider how we will organise rotations and take the opportunities to minimise loads in the system and reduce the opportunities for pathogens to cause yield loss," he said.

Between them, 265 paddocks were surveyed: and 50 plants per paddock were sampled in crops of barley, wheat and Durum.

Distribution of winter cereal survey sites across the northern region in 2019. Grpahic: GRDC

Distribution of winter cereal survey sites across the northern region in 2019. Grpahic: GRDC

"The important thing to remember when looking at the results is that they are from plant material only," Mr Milgate said.

"They cannot be directly related to the results from the normal PREDICTA® B platform because they include soil and stubble in their samples."

Mr Milgate noted they were only considering what was in the plants.

"We were also conducting some followup stubble infection and spore release experiments following on from the survey looking at paddocks where we had contrasting results from leaf diseases from 2019," he said.

"The survey gives a really good overview of the general trends."

When analysing those results, Mr Milgate said the drought last year highlighted obvious trends in foliar pathogens where the northern regions of the state had much lower levels of disease.

"We can clearly see from wheat and barley that the southeast of NSW had experienced better growing conditions last year and more development of foliar pathogens in the base of the plants," he said.

"They did not cause economic damage in those crops but there was potential for them to develop and move into the upper canopy had the season been much better."

Diseases detected in southern and central NSW crops included Spot form of net blotch (SFNB) and yellow leaf spot in barley: while yellow leaf spot and Septoria tritici blotch in wheat.

"One was a surprise to us was the consistent yellow leaf spot in the barley plants and that was across the region," Mr Milgate said.

"In wheat, the dominant pathogen across the entire region was yellow leaf spot.

"In the southern and central areas Septoria tritici blotch is more important."

Another pathogen the research found using the available technology was Stagonospora nodorum blotch and Mr Milgate said it is under investigation to see to what extent it will influence production on the eastern seaboard.

"It is a disease more recognised in WA as a significant problem, although we have records of it occurring in eastern Australia," he said.

"But we rarely see it causing economic damage."

Mr Milgate further addressed the complex issue of root diseases in winter cereal crops and said in almost every paddock they noted a combination of diseases detected in the root systems.

He identified common root rot, crown rot, Pythium and take- all as the diseases of serious concern.

"It was confronting to see the amount of crown rot seen in plants last year," Mr Milgate said.

"Being a drought year was particularly favourable for the development of crown rot with high levels of detection north to south."

Traditionally, crown rot was thought of as a northern NSW issue, but in the past decade many research projects have identified increasing levels of disease developing in southern and central NSW.

Mr Milgate warned growers across the south to be aware excellent seasonal conditions have been conducive to the chance of further spread of crown rot.

"The good early season actually allows the pathogen to infect the plants, however if we see mild spring conditions yield loss will not be high, but inoculum levels will be high," he said.

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