Both net blotches are being found in barley
- Williams
- Crossman
- Esperance
Agworld users have reported finding both spot-type net blotch (STNB) and net-type net blotch (NTNB) in barley crops (variety unknown) near Williams and Crossman.
Plant pathologist Andrea Hills (DPIRD) has reported finding NTNB and STNB in a booting Oxford barley crop near Esperance. The crop had widespread infection of these diseases. It also has oat aphids. The crop will be sprayed with AviatorXpro®.
Applying a fungicide spray is necessary in medium to high rainfall regions where disease threatens crops with high yield and quality expectations. A wide range of foliar fungicides are registered for NTNB. 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.
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.
Details on which foliar fungide 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 these diseases. If growers suspect that fungicides have reduced efficacy in their paddocks, they can contact the CCDM’s Fungicide Resistance Group at frg@curtin.edu.au. 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 latest Research uncovers new changes in fungicide resistance in WA barley media statement.
Growers with significantly higher levels of NTNB disease infection are encouraged to collect plant samples before they are sprayed and send them to the department to aid identification and assist research to learn more about this new pathotype. Growers sending samples with suspected NTNB to the department can contact DPIRD technical officer Simon Rogers on +61 (0)8 9368 3445.
For further information on symptoms and management of STNB refer to;
- Managing spot type net blotch in continuous barley page
- Managing net-type net blotch of barley in Western Australia page
- GRDC’s Spot and stop barley blotch this winter media statement.
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.