Barley disease update and current management recommendations
The PestFax team received quite a few barley disease reports this week. The diseases may have become visible after recent rainfall. Reports are predominantly coming from crops in the Albany and Esperance port zones with some reports of spot-type net blotch from the central agricultural region.
Blotches
- Nokaning
- Muntadgin
- Coomaldannerup
- Woogenellup
- Moonigurrup
- Wittenoom Hills
Crop protection officer Kylie Chambers (DAFWA) has found spot-type net blotch (STNB) in seedling barley crops, sown onto barley stubble, at Nokaning and Muntadgin.
Crop protection officer Alice Butler (DAFWA) has reported finding STNB in a tillering barley crop at Coomaldannerup and net-type net blotch (NTNB) in a tillering Flinders barley crop at Woogenellup and a tillering barley crop (variety unknown) at Moonigurrup.
Plant pathologist Andrea Hills (DAFWA) has seen STNB at low levels in a tillering La Trobe barley crop near Wittenoom Hills. The crop was also displaying signs of physiological leaf spotting, which is expressed when plants are under stress.
For further information on symptoms and management of blotches see DAFWA’s Managing spot type net blotch in continuous barley and Managing net-type net blotch of barley in Western Australia pages.
Barley leaf rust, scald and powdery mildew
- South Stirling
- Borden
- Kendenup
- Wittenoom Hills
James Bee (Elders) has reported finding low levels of barley leaf rust (BLR) in tillering Planet, Oxford and Flinders barley crops near South Stirling. Only 1-3 rust pustules were found on older leaves on most plants and the BLR was at early stage infection but James commented that BLR is likely to become widespread throughout the area due to the presence of rusty volunteer barley in pasture paddocks. James also found low levels of scald in these barley crops.
Plant pathologist Kithsiri Jayasena (DAFWA) has reported finding trace levels of BLR in a seedling (Z25) Planet barley crop near Borden. The crop had been treated with Impact in-furrow and the farmer had sprayed the crop with propiconazole this week. Kith has also found trace levels of BLR in a seedling (Z25) Flinders barley crop east of Kendenup. The crop had been seed treated with Baytan® and Gaucho®. The grower will continue monitoring the crop and will spray with a foliar fungicide.
Quenten Knight (Precision Ag) has found low levels of BLR and powdery mildew in a tillering Baudin barley crop at Wittenoom Hills.
For more information on BLR and how to manage it refer to DAFWA’s Diagnosing barley leaf rust page and the 2017 PestFax newsletter Issue 4 Barley and wheat leaf rust warning for 2017 article.
For more information on barley powdery mildew and scald refer to DAFWA’s Management of barley powdery mildew in 2017 and Diagnosing barley scald pages.
Current recommendations for managing barley diseases
In the face of a tight season in many areas, the decision whether or not to apply fungicide will vary with the disease and barley crop type (malt vs feed barley). Careful thought needs to be given to yield outlook and potential for disease to progress prior to investing in fungicide.
Net blotches
At this time blotches are likely to be an issue only for barley on barley crops. Crops sown with Systiva® or Uniform® should not be exhibiting significant levels of disease. Most varieties are susceptible to spot type net bloth (STNB) and the varieties Bass, Flinders and Oxford are likely to be vulnerable to net type net blotch (NTNB).
Prolonged dry weather does not favour disease development or response to fungicide application for these diseases. DAFWA trials show yield loss from STNB is very dependent on seasonal conditions with winter/spring rainfall an important driver of disease development and yield impact. Application of fungicide prior to stem extension (for example, tillering) can reduce disease but will need follow-up spray later to give yield response. Trials do not indicate a penalty from waiting till late tiller/stem extension for application.
Barley leaf rust
Where there was a green bridge infected by BLR then paddocks are at risk and growers and consultants are urged to monitor paddocks for rust on a weekly basis, reports received suggest that some barley crops in the lower great southern fit into this category.
Most varieties will be susceptible at this early stage, even those varieties with adult plant resistance (APR), such as Flinders, Oxford or Planet.
Plant pathologist Kithsiri Jayasena (DAFWA) advises growers and consultants not to underestimate the leaf rust pathogen. As long as the susceptible host is present the rust can survive. These infected plants, such as in volunteer barley, will produce millions of rust spores and will spread via the wind. When these spores land on leaves of susceptible barley and the leaves are wet, then the spores will start germinating and infect the plant. This process will continue until the plants mature and die.
This season there are drier areas, especially in the northern and eastern agricultural regions of WA where barley leaf rust inoculum is unlikely to be present in significant levels, but conditions are very different in the lower great southern region. Kith says in this region, if the local area is dry but experiencing early morning dew and the crops are infected, then it is worth incorporating fungicide into the post weed control program at mid tillering or to wait until the early stem elongation stage and spray.
If the barley seed was treated with fluxapyroxad seed dressing prior to seeding or seeded with an in-furrow fungicide containing actives such as azoxystrobin with metalaxyl M, this will suppress the leaf rust development. In this situation growers can delay spraying any foliar fungicide and keep monitoring. The second spray will be depend on the how season progress. If no rain and no dew is present and crops are infected then fungicide spraying can be delayed and growers and consultants keep monitoring.
Scald
Growers and consultants need to know their variety resistance. The varieties Oxford, Flinders and Rosalind are moderately susceptible (MS) so will be at some risk, while LaTrobe is moderately resistant (MR) and should be okay. As with the net blotches, prolonged periods of dry weather do not favour scald development.
If the paddock is rusty then a fungicide application will help with both diseases.
Paddocks treated with a fluxapyroxad fungicide seed dressing should be protected.
Powdery mildew
Seed dressing or in-furrow products applied to manage other diseases may provide some degree of protection from powdery mildew.
The compromised triazole ingredients tebuconazole and triadimefon will have reduced efficacy and are not recommended for powdery mildew control. Any use of tebuconazole increases the selection pressure on the fungicide resistant strains of powdery mildew.
Products containing other triazole fungicide active ingredients like epoxiconazole (for example, Opus®), prothioconazole + tebuconazole (for example, Prosaro®) or propiconazole (for example, Tilt®), should have uncompromised activity against powdery mildew.
For greatest efficacy, fungicides should be applied before significant levels of disease establish in crop.
Barley foliar fungicide information can be found at DAFWA’s Registered foliar fungicides for cereals in Western Australia.
For more information contact Kithsiri Jayasena, Plant Pathologist, Albany on +61 (0)8 9892 8477, Geoff Thomas, Plant Pathologist, South Perth on +61 (0)8 9368 3262, Andrea Hills, Plant Pathologist, Esperance on +61 (0)8 9083 1144 or Ciara Beard, Plant Pathologist, Geraldton on +61 (0)8 9956 8504.