Take-all could pose a significant risk to southern NSW wheat crops this year, prompting calls for growers to prioritise PREDICTA B testing in the lead-up to the winter season.
Results from PREDICTA B DNA-based soil tests suggest that take-all levels have increased on last year and could be among the highest levels seen for some time.
The Grains Research and Development Corporation is urging growers to assess take-all, crown rot and root lesion nematode (Pratylenchus neglectus and P. thornei) risk before planting by using the PREDICTA B service to assist with crop and variety selection as well as paddock management.
South Australian Research and Development Institute soil biology and diagnostics research leader Alan McKay said take-all was emerging as the greatest soil-borne disease risk to wheat in southern NSW this year, with 38 per cent of paddocks tested so far in 2017 rated medium to high risk.
By comparison, 19 per cent of paddocks have been rated medium to high risk for either crown rot or root lesion nematode.
‘‘The risk from take-all will be greatest for wheat following grassy pastures or other cereal,’’ Dr McKay said.
‘‘Summer rainfall will have reduced the risk of take-all in some areas, but how much this risk has reduced will depend on how long the soil remained moist to allow microbial activity to break down infected roots and crowns which harbour the take-all fungus.
‘‘This will vary with the amounts of rainfall, soil type and summer weed control.
‘‘If growers are planning to sow wheat following grassy pastures or a cereal crop, we recommend getting the paddock checked by PREDICTA B.’’
PREDICTA B requires a dedicated sampling strategy and is not a simple add on to a soil test.
Sampling recommendations are:
■Collect three small cores (1cm diameter and 10cm deep) from each of 15 different locations within the target production zone within the paddock.
■Take the soil cores from along/in the rows of previous cereal crop, if these are still visible, and retain any stubble collected by the core (most soil-borne pathogens are concentrated under the rows of the last cereal).
■If the rows can’t be seen, take the cores at random.
■Taking the soil sample in the inter-row, where pathogen concentrations are lowest, is only recommended if a susceptible crop is to be sown between the rows and a grower wants to know if inoculum levels are low enough to take the risk.
■Add one piece of cereal stubble (if present) to the sample bag at each of the 15 sampling locations. This improves the detection of crown rot and other stubble-borne pathogens. Each piece should be from the base of the plant and include the crown to the first node (discard material from above the first node).
■The maximum sample weight should not exceed 500g.
■For more information on the PREDICTA B tests or to access the testing service, visit: http://pir.sa.gov.au/research/services/molecular—diagnostics/predicta—b