Circumvent early crop disease risks
If weeds and/or volunteer crop plants are present at the start of this new cropping season, particularly in or adjacent to cropping paddocks, there is a greater risk of spread of pests and diseases to newly emerging crops.
Volunteer regrowth has been reported in several areas of the wheatbelt this year with wheat stem rust and barley net blotches found in regrowth barley at South Stirling (lower great southern).
You can employ some proactive management strategies to minimise potential disease impacts on your crops this season.
Biotrophic diseases
Biotrophic diseases are carried over on green bridge (volunteer plants, weeds).
These include rusts on wheat and barley, and mildew on wheat, barley, oats and canola.
Root (take-all, rhizoctonia, common root rot) and crown (crown rot) diseases, and nematodes (cereal cyst nematode, root lesion nematode) can also be supported by a green bridge.
Management strategies – remove the green bridge by use of herbicides and grazing at least four weeks prior to seeding, use registered fungicides at seeding (seed dressing or in-furrow) in areas at risk of early disease.
Necrotrophic diseases
Necrotrophic diseases are carried over on stubble and include powdery mildew, wheat yellow spot and Stagonospora (septoria) nodorum, barley scald and net blotches, canola blackleg, sclerotinia stem rot (when sclerotes present in the stems) and white leaf spot, field pea black spot, chickpea ascochyta, cereal crown rot and take-all.
Management strategies - crop rotation with good grass weed control and avoiding sowing alongside or downwind of infected stubble, use registered fungicides at seeding (seed dressing or in-furrow).
Diseases carried by vectors
Diseases carried by vectors such as aphids or mites which survive summer on green bridge include barley yellow dwarf virus, wheat streak mosaic virus, and beet western yellows virus.
Management strategy – remove the green bridge.
Seed borne diseases
These include anthracnose in lupins, ascochyta in chickpea, barley scald, cereal smuts and bunts, net-type net blotch (but not considered a big risk when compared to blown in infection from wind borne spores), and wheat streak mosaic virus.
Management strategies – seed testing, get new clean seed, use registered fungicides at seeding (seed dressing or in-furrow).
Soil borne diseases
These include lupin brown spot, common bunt of wheat, flag smut of wheat, covered smut of barley, loose and covered smut of oats, root diseases (common root rot, rhizoctonia, Pythium root rot, take-all) and nematodes (cereal cyst nematode, and root lesion nematode).
Management strategies – soil testing (particularly if you observed any uneven growth or bare patches in your crops last year), crop rotation with good weed grass control, fallow, use registered fungicides at seeding (seed dressing or in-furrow).
Where sclerotinia stem rot has previously occurred, sclerotinia fruiting bodies called sclerotes can survive in soil for up to six years infecting canola, lupins, chickpeas and lentils. So non-host species, such as cereals, should be grown for at least three years in paddocks that were recently affected.
Some other key tips:
- Plan variety choices and crop rotations to minimise disease risks. Find out more crop specific disease management and the disease ratings of different varieties on the Crop Disease webpage of the Department of Primary Industries and Regional Development (DPIRD) website.
- Monitor and report to PestFax any presence of disease on volunteer cereals or early sown crops.
- Consider use of registered seed or in-furrow fungicide treatments for seed-borne or other diseases your crop could be at risk of (including foliar and root diseases) to avoid the need for early fungicide sprays if early disease strikes. See the crop disease webpage for more information.
- Be aware of foliar fungicide product registrations, limits on number of times a particular mode of action can be used on a crop per season, optimal timing and rates of sprays for effective control, and withholding periods for grazing and harvesting.
- Check out the PestFax map showing what diseases were reported from your area last season to give you an idea of what diseases might be a higher risk next season. Be sure to subscribe to the PestFax newsletter if you haven’t already to receive information on pest and disease finds across the WA wheatbelt next season.
The following webpages contain additional useful information:
- Crop diseases: forecasts and management
- Control of green bridge for pest and disease management
- Registered foliar fungicides for cereals in Western Australia
- Seed dressing and in-furrow fungicides for cereals in Western Australia
For further information contact
Ciara Beard, Plant Pathologist, Geraldton on +61 (0)8 9956 8504,
Geoff Thomas, Plant Pathologist, South Perth on +61 (0)428 947 287 or +61 (0)8 9368 3262,
Kith Jayasena, Plant Pathologist, Albany on +61 (0)8 9892 8477,
Andrea Hills, Plant Pathologist, Esperance on +61 (0)8 9083 1144,
Ravjit Khangura, Canola plant pathologist, South Perth on +61 (0)8 9368 3374,
Brenda Coutts, Virologist, South Perth on +61 (0)8 9368 3266,
Sarah Collins, Nematologist, South Perth on +61 (0)8 9368 3612,
Daniel Huberli, Plant Pathologist (root diseases), South Perth on +61 (0)8 9368 3836.