White leaf spot.
PHOTO: Steve Marcroft
Seasonal conditions and an increase in area planted to canola in 2013 meant the season was a bumper one for fungal diseases. Blackleg severity increased across all cultivars evaluated at blackleg monitoring sites in southern New South Wales and northern Victoria, and the mild winter followed by rainfall in July and August provided ideal conditions for sclerotinia.
‘Minor’ diseases of canola such as alternaria and white leaf spot were also observed.
The National Canola Pathology Project is a five-year project co-funded by the GRDC, which aims to take a nationally coordinated approach to canola pathology and disease management. It provides pathology support to the canola industry and key pathology contacts in each state.
While the focus of the project is on the big-ticket items – blackleg and sclerotinia – it is also examining the impact of other diseases, including white leaf spot, alternaria and powdery mildew.
Plant pathologist Kurt Lindbeck, from the NSW Department of Primary Industries, says there are several things growers can look out for this season to assess their sclerotinia risk.
Speaking at the recent GRDC Updates, Mr Lindbeck said: “Factors such as the frequency of canola in your district and in the cropping rotation, late-winter rainfall, frequency of past sclerotinia outbreaks and timing of flowering will all provide an indication of the likelihood of sclerotinia occurring in the season.
“If you produce canola in a district where outbreaks of sclerotinia frequently occur and the seasonal outlook is favourable for spring rainfall, consider a foliar fungicide to minimise potential yield loss.
“Crop monitoring is very important at the end of the season. By determining the final level of disease development, you can see if your current disease-management strategies have been successful or may require change. It also gives a baseline from which comparisons can be made in future seasons.”
The final stage of the sclerotinia life cyle is the production of sclerotia in infected stems. These sclerotia can survive freely in the soil for at least five years.
PHOTO: Kurt Lindbeck
Foliar fungicides can provide effective control when applied correctly. Application is economical only when a high level of infection is likely and yield potential is high.
When considering a fungicide application, look at the:
- timing, which is critical;
- high water rates, which are required for good coverage; and
- flowering, as application is most effective at 20 per cent bloom (14 to 16 flowers off main stem) to 30 per cent bloom (about 20 flowers off main stem).
Aim to apply product to early flowers and penetrate the lower crop canopy to protect the main stem and leaves before symptom development (stem lesions).
Use products containing procymidone or iprodione. Prosaro® is also registered for use at 20 to 50 per cent bloom.
Pulse crop diseases
Wet winter conditions throughout July and August in 2013 in southern NSW favoured the appearance of several pulse diseases.
Phytophthora root rot of lupins requires only a brief period of waterlogging – as little as eight hours – for infection of the roots and plant death to occur. The disease presents as dead patches in the crop.
Conditions also favoured the development of powdery mildew of field peas in some districts. There are several foliar fungicides and resistant varieties available to combat this disease.
Disease in manure crops
There is an increasing trend towards using pulse crops as manure in southern NSW and northern Victoria, and this is resulting in an increase in some diseases, in particular blackspot (or ascochyta blight) of field peas.
Mr Lindbeck issued a caution to those using pulse crops for manure. “If pulse crops are to be used successfully for manuring purposes, the balance has to be made between dry-matter production and disease management.
“Many pulse crops have not been developed as manure crops and the agronomy and disease management packages that accompany these crops traditionally focus on grain production.”
Blackspot Manager is a computer-based model that predicts the best time to sow new-season field pea crops and will be available to field pea producers and advisers in southern NSW this year. It calculates the timing of spore release from old field pea stubble based on seasonal rainfall and temperature data, so producers can sow crops to avoid high disease pressure conditions.
Blackspot Manager has been available to growers in Western Australia for several years, and has recently been rolled out to field pea producers in South Australia and Victoria. In the past two years, data from southern NSW has been supplied to Department of Agriculture and Food, WA, researchers to allow the model to be extended into the region.
02 6938 1608,
Email Kurt Lindbeck to register for the Crop Disease Bulletin e-newsletter.
A fact sheet on Blackleg Management is available at: www.grdc.com.au/GRDC-FS-BlacklegManagementGuide
A fact sheet on Sclerotinia Stem Rot in Canola is available at: www.grdc.com.au/GRDC-FS-SclerotiniaInCanola
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