Scald (Rhynchosporium commune) is a stubble- and seed-borne disease which is favoured by high rainfall environments. Generally, this disease is most damaging in the high rainfall, southern regions but severe epidemics have been observed in medium rainfall areas under favourable conditions. Details and more photos of the symptoms of scald are available on the MyCrop page.
- Sowing resistant varieties where possible is the most effective strategy. For medium to low rainfall areas, avoid very susceptible (VS) varieties. For high rainfall areas, sow moderately resistant (MR) and resistant (R) varieties.
- Rotating crops (for example, a break of one year) between barley crops will significantly reduce the potential for serious disease.
- Sow clean seed harvested from an uninfected crop.
- A seed dressing or in-furrow fungicide should be used in medium to high rainfall areas or if the seed is from an infected crop.
- Applying a fungicide spray is necessary in medium to high rainfall regions where disease threatens crops that have high yield and quality expectations. Apply fungicide before head emergence if hot spots within the crop are frequently observed during stem elongation or active infections are present on middle canopy leaves.
Powdery mildew (Blumeria graminis f.sp. hordei) occurs throughout the agricultural areas but is more common in southern regions where high humidity favours disease development. Severe infections can occur in winter months during the early stages of the crop growth, thus affecting yield potential through tiller abortion (up to 25% yield loss). New leaves that emerge later in the season are generally less severely infected as conditions become less favourable to the disease. This may not be the case in high production situations (such as high rainfall or humid coastal areas) where high seed rates or heavy application of nitrogen fertiliser have been used. Severe infection at later stages (after Z39) can cause 5-13% yield loss. A powdery mildew infected crop will appear yellow from a distance, similar to a crop suffering from water logging or nutrient deficiency. Therefore, close examination is needed. Details and more photos of the symptoms of powdery mildew are available on the MyCrop page.
- Using resistant varieties will minimise the impact of powdery mildew and most economical way to manage the disease. Some current malting varieties such as Granger, Flinders and Scope CL and some feed varieties such as Dash and Oxford grown in WA are resistant to powdery mildew. See the Crop Sowing Guide for disease resistance profile.
- Cultural control such as eradication of regrowth barley which harbour inoculum, disposal of infected stubbles, avoiding early sowing and avoiding use of excess nitrogen fertiliser application will help to reduce the disease.
- A seed dressing fungicide containing fluquinconazole applied as a standard treatment for susceptible varieties is usually sufficient to minimise early disease development and limit the yield loss caused by powdery mildew in medium to high rainfall areas. The duration of early protection depends on the amount (grams per tonne of grain) of active ingredient applied to grain. Higher rates will increase the duration of protection. In-furrow application with fertiliser allows the use of higher rates of fungicide than direct seed application, however fungicide resistance has diminished the control provided by flutrifol and triademfon in-furrow.
- In situations where varieties susceptible to powdery mildew are sown without seed dressings, it is important to spray the crop if there are early signs of mildew, especially during the tillering stage. Application of foliar fungicides is most economical in high risk areas or in regions with high yield or quality expectations. For greatest efficacy, fungicides should be applied before significant levels of disease establish in crop. Use the fungicide to protect the crop rather than attempt to recover the crop. The first foliar fungicide spray may coincide with post-emergent herbicide application at tillering. A second spray may be warranted before head emergence, three to four weeks after the first spray, if active infections are visible on leaves which have emerged subsequent to the first fungicide spray.
- Due to the development of fungicide resistance in the powdery mildew pathogen there are special considerations on which up-front and foliar fungicides are used for powdery mildew control. Tebuconazole based fungicides should not be used in any areas due to being compromised by fungicide resistance. In high powdery mildew risk, high rainfall areas such as south coast of WA, triadimefon and tebuconazole single active base products are not recommended. Epoxionazole, Propiconazole, Propiconazole + Cyproconazole, Propiconazole + Tebuconazzole, Tebuconazole + Prothiconazole base single actives or mixtures can be use in managing powdery mildew. The fungicide mixtures currently registered in WA which containing strobilurins (Cyproconazole + Azoxystrobin, Tebuconazole + Azoxystrobin, Epoxiconazole + Azoxystrobin and Epoxiconazole + Pyraclostrobin) are recommended to use only one application for a season as part of the fungicide resistance management strategies. See Management of barley powdery mildew in the face of fungicide resistance for further information.
- Barley growing on potassium deficient soil (K <50ppm) is more susceptible to powdery mildew. Consider applying potassium fertiliser, preferably muriate of potash 20-50kg/ha (or sulfate of potash 44-97kg/ha), four weeks after seedling emergence in order to reduce the powdery mildew and increase yield. Muriate of potash has been found to be significantly better than sulfate of potash in aiding powdery mildew control.