Dont let diseases reduce your crop potential
You can employ some proactive management strategies to minimise potential disease impacts on your crops this season. Weeds and/or volunteer crop plants present at the start of the new cropping season, particularly in or adjacent to cropping paddocks, pose a greater risk of spread of pests and diseases to newly emerging crops.
Biotrophic diseases are carried over on green bridge (volunteer plants, weeds). Biotrophic diseases 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 (https://www.agric.wa.gov.au/barley/root-disease-under-intensive-cereal-p...) and nematodes (cereal cyst nematode, root lesion nematode) (https://www.agric.wa.gov.au/barley/root-lesion-and-burrowing-nematodes-d...) can also be supported by a green bridge. Management strategies – Remove the green bridge by using herbicides and grazing at least four weeks prior to seeding, use of registered fungicides at seeding (seed dressing or in-furrow) in areas at risk of early disease.
Necrotrophic diseases are carried over on stubble and include powdery mildew, wheat yellow spot and Parastagonospora (septoria) nodorum, barley scald and net blotches, canola blackleg 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, avoid sowing alongside or downwind of infected stubble, and use of registered fungicides at seeding (seed dressing or in-furrow).
Diseases carried by vectors such as aphids or mites that survive summer on green bridge include barley yellow dwarf virus, wheat streak mosaic virus, and beet western yellow virus. Management strategy – Remove the green bridge.
Seed borne examples include anthracnose in lupins, ascochyta in chickpea, barley scald, cereal smuts and bunts, net-type net blotch, which is not considered a big risk when compared to infection from wind borne spores, and wheat streak mosaic virus. Management strategies – Seed testing, new clean seed, use of registered fungicides at seeding (seed dressing or in-furrow).
Soil borne – examples 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 uneven growth or bare patches in crops last year,
crop rotation with good weed grass control, fallow, and use of registered fungicides at seeding (seed dressing or in-furrow).
Where sclerotinia stem rot has previously occurred, sclerotinia fruiting bodies called sclerotes can survive in stubble and 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. Be aware of the risk factors associated with each crop disease and variety - give preference to varieties with some disease resistance. Crop rotation is particularly important for reducing the risk of stubble borne and soil borne diseases. Find out more crop specific disease management and the disease ratings of different varieties on the DPIRD website
- Monitor and report to PestFax the presence of disease on volunteer cereals or early sown crops.
- Consider the use of registered seed or in-furrow fungicide treatments (https://www.agric.wa.gov.au/barley/seed-dressing-and-furrow-fungicides-c...) 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, should disease strike early. Information on registered seed dressing and in-furrow fungicides for cereals is available on the crop disease webpage.
- 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. Foliar fungicide registration charts for cereals, canola and lupin are available on the crop disease webpage and spray strategies are outlined on specific crop disease management pages.
- Check out the PestFax map, which shows the diseases that were reported from your area last season and will give you an idea of the diseases you might be at a higher risk of this season. Be sure to subscribe to the PestFax newsletter if you haven’t already, to receive information on pest and disease reports across the WA Wheatbelt next season.
- Download canola disease apps to assist with in-season management. BlacklegCM and SclerotiniaCM are free apps available for tablets from the App store or Google play. They provide guidance for economic application of fungicide for managing blackleg and sclerotinia respectively.