New South Wales and southern Queensland grain growers are being reminded that vigilance will be the key when it comes to monitoring and managing disease to protect yield in cereal crops this season.
Recent rainfall patterns have provided ideal conditions for the development of root and foliar diseases this winter increasing the need for growers to have a strategic and disciplined approach to disease management.
GRDC Crop Protection Manager – North, Vicki Green said many areas across the northern region were experiencing their wettest winter since 2016 making it critical for growers to monitor crops regularly and send samples of suspect plants to pathologists for testing to ensure accurate disease identification.
"Growers are well aware that vigilant disease management is the key to protecting yield and maximising profit in cereal crops," she said.
"It has been very wet across many parts of NSW and southern Qld, which impacted sowing, while the frequent rainfall and cold temperatures have had an effect on crop development and disease levels.
"Given the conditions and both the agronomic and disease issues in paddocks, we are emphasising the importance of growers getting a correct diagnosis so they can implement effective, appropriate management programs that deliver a worthwhile return on investment."
Diseases on the 'watch list' in cereal crops this season include yellow leaf spot in wheat; stripe and leaf rust in wheat; powdery mildew in wheat; and net blotches in barley.
NSW Department of Primary Industries senior plant pathologist Steven Simpfendorfer said his team had already processed more than 280 diagnostic samples and enquiries from growers and advisers this season.
"There is plenty of cereal disease around, but with wet soils and intermittent frosts there has also been a fair bit of physiological leaf responses in wheat and barley that are not disease related," he explained.
"So correct diagnosis and pathology support remains critical to ensure appropriate management strategies are put in place."
GRDC is hosting an online webinar next Thursday, August 26 that includes a seasonal update on cereal diseases with Dr Simpfendorfer; as well as tactics for managing crown rot in the farming system; and the latest in Ascochyta blight in chickpeas. The webinar starts at 9am (AEST).
While in Queensland, Department of Agriculture and Fisheries (DAF) pathologist Lisle Snyman said a delayed planting meant disease levels were currently lower than in NSW, but infection rates were likely to increase if wet conditions persisted.
"If the forecast for wet weather continues into spring then I would anticipate that disease will be an issue across parts of Queensland. Sampling will be critical so growers know exactly what they are dealing with in the paddock," she said.
Dr Simpfendorfer said there had been surprising amounts of yellow leaf spot in wheat crops after drier seasons through 2017-2019. While stripe and leaf rust levels in susceptible dual purpose winter wheats are placing increased rust pressure on later sown susceptible spring wheat varieties across northern and central-west NSW.
"Net blotch has also been prevalent in 2021 barley-on-barley rotations. There have also been a few situations this season where yellow spot or net blotch infection is occurring at the edge of crops adjacent to wheat or barley stubble from 2020 which is in fallow," Dr Simpfendorfer said.
"Spores are blowing in off this infected stubble. This tends to occur a lot more in fallow situations compared with having any winter crop planted in these paddocks as a break crop, which restricts wind dispersal from infected cereal stubble."
He said the biggest challenge with yellow leaf spot and net blotch remained fungicide spray timings when early (pre-GS30) infections occur.
"Growers often want to apply in-crop herbicide during tillering and include a fungicide, but this is not actually a disease control spray as the key yielding leaves have not emerged so this treatment will have very little impact on inoculum load as infection keeps coming off stubble throughout the season," Dr Simpfendorfer said.
"It is far more effective to apply a fungicide at GS30-32 when the flag-2 leaf has emerged."
On a positive note, he said stripe rust pressure in central and northern NSW was generally lower in 2021 than 2020.
"We learnt our lesson with the Yr198 pathotype and poorly managed infection levels in highly susceptible winter wheats, such as DS Bennett creating disease pressure for main season wheat last season," Dr Simpfendorfer said.
"However, stripe rust is sneaking into crops in some areas, with one control option for mixed farmers being to crash graze crops. However, this is often ineffective due to current low stock numbers only providing patchy grazing that allows rust development to continue in lightly grazed areas."
He said encouragingly there was a reasonable level of awareness and concern about wheat powdery mildew (WPM) even though there had been limited reports of WPM occurrence to date this season.
"The levels of fungicide resistance and reduced sensitivity in NSW and Victoria populations of WPM last season is concerning for industry, but growers are increasingly aware of the best management practices," Dr Simpfendorfer said.
"Overall fungicide supplies currently appear adequate this season, but many growers and agronomists across NSW are trying to determine risk levels going forward and are working to secure supplies now."
Looking ahead the experienced pathologist warned if the season remained wet into flowering there may be an increased risk of Fusarium head blight (FHB). Dr Simpfendorfer said to add to the concern the only product registered for FHB control in Australia was Prosaro (prothioconazole + tebuconazole) which may also be in demand for disease management in canola.
The identification of fungal cereal diseases can provide valuable information to help with crop rotation planning, variety and paddock selection for subsequent seasons. It also provides vital information for GRDC's crop disease surveillance programs to stay in-front of changes in pathogens to guide breeding efforts and the potential development of fungicide resistance.
Any winter cereal crops (wheat, durum, barley, oats or triticale) which are showing signs of disease should be sampled and sent away for testing by NSW DPI. Cereal disease diagnosis can be obtained by sending an infected tissue/plant sample in paper packaging (paper bags, envelopes or wrapped in newspaper) to:
Queensland – Lisle Snyman, DAF QLD, Hermitage Research Facility, 604 Yangan Rd, Warwick QLD 4370; 07 4542 6761.
Northern NSW – Dr Steven Simpfendorfer, NSW DPI, 4 Marsden Park Rd, Tamworth NSW 2340; 0439 581 672.
Southern NSW – Dr Andrew Milgate, NSW DPI, Wagga Wagga Agricultural Institute, Pine Gully Road, Wagga Wagga NSW 2650; 02 6938 1999.
