Published on 27/07/2022
Until recently this was the case in New Zealand; net blotch was at the bottom of the list of key barley diseases.
How things have changed.
Two seasons ago the Bayer field team beganto see an increase in the level of net blotch in barley crops. Then last spring the incidence of net blotch increased significantly.
Net blotch used to be a disease of second year barley crops but now it is infecting many first-year barley crops.
What might have changed?
A key inoculum source for net blotch is stubble and while this explains the incidence in second year barleys, it doesn’t for first year crops. For these crops barley stubble simply won’t be present.
Research suggests infection from volunteer crops or long-distance spore dispersal are unlikely as infection sources.
And while climate change may be making conditions more favourable for net blotch infection within the paddock, it doesn’t explain the initial infection source.
One possible source of net blotch infection is the seed. Barley seed can be infected with net blotch and it is important to use a seed treatment that provides effective control of seed borne net blotch.
Hopefully the reason net blotch is increasing will be answered with time, but for this spring the important thing is to ensure the disease is successfully controlled.
For the successful control of net blotch, it is important to use the correct fungicides as not all control the disease and to understand that infection starts during the winter.
Bayer produces several fungicides which all control net blotch.
The DMI fungicide prothioconazole, the strobilurin fungicide trifloxystrobin and the SDHI fungicides bixafen and isoflucypram are available in the fungicide products Proline, Prosaro, Delaro, Aviator Xpro, VIMOY iblon and CALEY iblon.
After conducting trials investigating disease control strategies for barley, Bayer now sup ports the application of fungicides at GS30,GS31-32 and GS39.
By starting at GS30, infection that took place in the winter is controlled and the GS31-32 and GS 39 applications maintain disease control through to the important flag leaf timing.
Applying Delaro at GS30 and again at GS31-32, with an application of Prosaro + VIMOY iblon at GS39, very effectively controlled net blotch, scald and leaf rust in Bayer trials.
This programme also resulted in a healthy crop which can help delay the onset of ramularia leaf spot.
This fungicide programme also utilises different modes of action which helps delay the development of fungicide resistance.
It seems that net blotch is here to stay as an important disease.
For next autumn it is important to practice sound agronomy practices such as making sure barley stubble is buried.
And it would be prudent to request seed treated with Raxil Star which is registered for the control of seed borne net blotch.
Words: Neil Waddingham, customer marketing manager, Bayer NZ.