Keep up with the latest research information on crop diseases including blackleg, sclerotinia, wheat rusts and septoria. The following papers were presented at the GRDC Updates across Australia in July and August 2017. Click the paper titles to view the full papers.
Author: Peter Cousins (Peter Cousins Consulting)
Date: 09 Aug 2017
- When spraying, be aware of the environmental conditions around you at all times.
- Read and adhere to the label. There are mandatory instructions on the label for some products.
- Know when to spray and when not to – is there an inversion?
- Keep your spray in your paddock.
Authors: Grant Hollaway, Mark McLean (Agriculture Victoria) and Andrew Milgate (NSW DPI).
Date: 23 Aug 2017
- Cereal diseases will need active management during 2017 following carry-over of high levels of inoculum on stubble and the green bridge after the wet spring of 2016.
- Consult a current disease guide to review your varieties’ resistance/susceptibility to the important diseases in the region and plan accordingly.
- There is resistance to fungicides in some important wheat diseases which highlights the need to rotate fungicide actives within crops and to implement integrated disease management strategies.
- Proactive disease management strategies are effective for disease control and provide economic return in seasons favourable for disease.
Authors: Robert Park (University of Sydney), Andrew Milgate and Will Cuddy (NSW DPI)
Date: 21 Jul 2017
- Few well adapted wheat varieties are currently available to Tasmanian growers that meet the minimum disease standard for leaf rust.
- To manage cereal diseases Tasmanian growers need to either accept lower yield potential with resistant wheat varieties or look to incorporate triticale into their rotations.
- Annual surveys have revealed that the Tasmanian septoria tritici blotch (STB) population has become dominated by isoforms (pathogens) with a high level of triazole resistance.
- To limit further fungicide resistance developing, fungicide resistance management practices must be implemented by growers.
- Integrated disease management complements fungicide resistance management.
- To slow fungicide resistance developing against the alternative modes of action, such as the succinate dehydrogenase inhibitors (SDHIs) and strobilurins, do not apply these more than once in a season
Authors: Susie Sprague (CSIRO ), Steve Marcroft (Marcroft Grains Pathology), Angela van de Wouw (University of Melbourne), Kurt Lindbeck, Rohan Brill and Col McMaster (NSW DPI).
Date: 03 Aug 2017
- In 2016 canola emergence in central-west of NSW coincided with blackleg spore release and wet seasonal conditions resulted in extreme levels of blackleg leaf lesions in some areas, particularly in cultivars with Group A resistance. However, crown canker severity was much lower than expected given the severe leaf infection.
- Upper canopy blackleg infection was severe in early-flowering crops with significant yield loss. Risk of yield loss associated with upper canopy infection can be reduced by selecting the correct variety for the sowing date.
- In 2017 dry conditions post-sowing delayed blackleg infection. Lesions observed in unprotected crops in early-mid June resulting from infection following widespread rain in the third week of May could progress to form crown cankers. Cold weather has slowed crop development, so flowering is not likely to not occur as early as in 2016. Although dry conditions are forecasted to persist, rainfall events in late winter and early spring could expose crops to blackleg spores during flowering and may promote upper canopy infection.
- White leaf spot and downy mildew have been widespread on canola seedlings in 2017. Both diseases are sporadic and do not generally affect grain yield
Authors: Kurt Lindbeck, Audrey Leo and Joop van Leur (NSW DPI)
Date: 25 Jul 2017
- Sclerotinia stem rot is a production issue where spring rainfall is adequate to provide long periods of leaf wetness in the presence of flowering canola crops.
- If there is a history of sclerotinia stem rot in your district causing yield loss, be prepared to use a foliar fungicide to reduce yield loss.
- Sclerotinia stem rot occurred in those districts with a frequent history of the disease in 2016. Wet conditions in spring were ideal for disease development.
- Extended periods of leaf wetness (approximately 48 hours) are ideal for triggering epidemics of stem rot.
- Foliar fungicides for management of the disease are best applied at 20% to 30% bloom for main stem protection
Authors: Lisa Kelly, Murray Sharman, Hugh Brier, Liz Williams, Duncan Weir (QDAF), Raechelle Grams, Jo White, Adam Sparks (Centre for Crop Health, Qld), Alan Mckay (SA Research and Development Institute).
Date: 19 Jul 2017
- Avoid paddocks with a history of Fusarium wilt in mungbean. Plant seed into well-drained soils and minimise plant stress.
- To minimise the risk of halo blight and tan spot: use low risk planting seed, plant varieties with higher levels of resistance, clean harvesting equipment, control weeds and volunteers, and use suitable crop rotations.
- Report phytoplasma disease outbreaks to Qld DAF Entomologists and Plant Pathologists.
- Timely fungicide applications of Folicur® (PER13979 – expires 30th June 2017; application for extension submitted, pending approval) or Custodia® (PER82104 – expires 30th November 2019) are effective at managing powdery mildew in mungbean. For Folicur, crops should be sprayed at the first sign of disease and then again 14 days later if necessary, with a maximum of three applications per crop. For Custodia, do not apply more than three foliar applications per season with a minimum retreatment interval of 10 to 14 days.
- Sorghum stubble is a good reservoir for Fusarium thapsinum to survive between sorghum crops.
- Level of F. thapsinum in sorghum stubble starts to decline after two months with standing stubble treatments appearing to decline at a slower rate than surface and buried treatments. By 18 months, F. thapsinum levels appear to be similar across all stubble treatments.
- PREDICTA B test for Macrophomina phaseolina is under evaluation.
Find this article useful? Tell us what you think by filling out this quick survey.