PREDICTA B tests for more pathogens

Know what lies beneath using new soil tests trialled in the northern region


Diseases
Ascochyta blight, shown here infecting chickpea seed pods, has been added to the PREDICTA B soil testing program after trials in the northern region. PHOTO GRDC

Ascochyta blight, shown here infecting chickpea seed pods, has been added to the PREDICTA B soil testing program after trials in the northern region. PHOTO GRDC

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Soil testing program expands to take in key diseases that can cut crop yields.

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Australia's popular PREDICTA B DNA-based soil testing service, which enables identification of disease pathogens, has been successfully extended to include six more diseases across three crops.

Dr Alan McKay, of the South Australian Research and Development Institute (SARDI) - which provides the PREDICTA B service with funding from the GRDC - says the program had been expanded.

New tests were put out last year in the northern region for:

  • Aascochyta blight and phytophthora root rot of chickpea
  • Yellow leaf spot and white grain disorder of wheat
  • Fusarium stalk rot and charcoal rot of sorghum.

Dr McKay says these are now reported in the 'tests under evaluation' section on PREDICTA B reports, along with combined levels of two arbuscular mycorrhizal fungi (AMF), to provide an indication of risk of long fallow disorder.

The new tests have the potential to save growers significant sums of money, he says.

Ascochyta is widely regarded as the most damaging disease on chickpeas and can cause virtual crop wipe-out in years of heavy infection.

Phytophthora root rot (PRR) is a serious pathogen of chickpeas that is widespread in the northern cropping zone and can cause 100p per cent loss in wet seasons. The phytophthora can survive on volunteer chickpeas, as well as on lucerne and medic.

Dr McKay warns that while the PREDICTA B test is useful for diagnosing PRR in affected crops, it should not be relied on to identify high risk paddocks before planting.

Research conducted by Sean Bithel, of NSW Department of Primary Industries, has found the phytophthora levels can drop to below detection limit of the assay within three to six months after harvest. So a non-detection does not provide certainty there is no threat of the disease.

However, if phytophthora is detected by the assay before sowing, growers should definitely consider not growing chickpeas in that paddock.

The new tests have the potential to save growers significant sums of money

Yellow leaf spot is a stubble-borne disease of wheat.

PREDICTA B test results can be used to: rank paddocks based on the levels of inoculum; monitor inoculum decline during different phases of the cropping sequence; and confirm disease diagnosis.

White grain disorder occurs sporadically in the northern region, especially in southern Queensland, but it remains unclear if the disease warrants an active management program.

It causes symptoms in grain that can lead to downgrading or rejection of affected wheat loads at receival sites.

PREDICTA B can identify the paddocks with potential to develop white grain disorder.

When seasonal conditions are conducive for infection, when it is wet during flowering and early grain fill, growers should check for symptomatic grain and plan to harvest high risk paddocks separately.

Charcoal rot affects more than 400 plant species and is a serious disease of summer crops including sorghum, soybean, mungbean and sunflower in the Northern region. The fungus is detected frequently by PREDICTA B in the northern region.

More information: Dr Alan McKay, SARDI, 08 8429 2216, alan.mckay@sardi.gov.au

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