More reports of spot-type net blotch in barley
- Goodlands to Pingelly
- Yerecoin to Merredin
David Stead (Anasazi Agronomy) reports that spot-type net blotch (STNB) is gathering momentum in Spartacus, La Trobe, Litmus and Planet barley crops (that have not been treated with Systiva® or Uniform®) across his advisory region (Goodlands to Pingelly and Yerecoin to Merredin). David commented that the varieties Bass and Banks are going pretty good at this stage. Some barley crops are at stem elongation (Z31) in this area.
Plant pathologist Andrea Hills (DPIRD) has reported finding STNB, varying in severity from less than 10% of crop with damage to widespread crop damage, in Planet barley crops near Esperance and Scaddan. The growth stages vary from tillering to stem elongation. The barley with widespread crop damage was a barley on barley rotation.
Barley varieties that are susceptible to STNB or net-type net blotch (NTNB) that have not been treated with a registered seed dressing against net blotches (ie Systiva® or Uniform®) and are sown into in a high risk situation (barley on barley) are particularly vulnerable. To see which barley varieties are susceptible to STNB and NTNB refer to DPIRD’s 2019 barley variety sowing guide for Western Australia.
Growers need to spray before STNB levels reach 5% leaf area infection. The most consistent responses for a first fungicide application timing have been recorded with fungicide application around stem elongation (Z30-31). In regions or seasons where spring rainfall will support disease development then applications around flag leaf - booting can show significant yield and quality benefits.
Applying a fungicide spray is necessary in medium to high rainfall regions where disease threatens crops with high yield and quality expectations. The choice of a single-spray or double-spray strategy depends on the environment in which the crop is growing, the time onset of disease and use of seed dressing or in-furrow fungicides:
- In high rainfall environments it may be necessary to apply two sprays, such as at early stem elongation stage with a follow-up spray three to four weeks later.
- In medium rainfall regions, consider one well timed spray between late stem elongation and early flag leaf emergence (Z33 - 39) to protect leaf two (flag-1). Under high disease pressure, best results may be obtained by using the maximum recommended rates.
Details on which foliar fungicide active ingredients are registered for STNB and NTNB can be found at DPIRD's Registered foliar fungicides for cereals in Western Australia.
Fungicide resistance is an emerging issue in net blotches. If growers suspect that fungicides have reduced efficacy in their paddocks, they can contact the CCDM’s Fungicide Resistance Group at firstname.lastname@example.org. More information on STNB fungicide resistance can be found at CCDM’s Spot form of net blotch debuts on the fungicide resistance list and GRDC’s GroundCover article Barley growers face net blotch resistance threat.
For further information on symptoms and management of blotches see DPIRD’s;
- 2019 PestFax Issue 7 article Net blotches found in barley crops and volunteers
- Managing spot type net blotch in continuous barley page
- Managing net-type net blotch of barley in Western Australia page.
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.
Article author: Cindy Webster (DPIRD Narrogin). Input by: Kithsiri Jayasena (DPIRD Albany).