Net Form of Net Blotch (NFNB)
By Boyd Coles / May 2019
Boyd is a Barley Agronomist based in Idaho Falls, ID. Boyd has a bachelor’s degree in Business Management from Idaho State University and has worked for Anheuser-Busch since June 1997.
Net blotch is a common disease of barley. It is caused by the fungus Pyrenophora teres and is favored by high humidity, rainfall, and sprinkler irrigation.
What to look for when diagnosing NFNB?
The net form of net blotch starts as pinpoint brown lesions, which elongate and produce fine, dark brown streaks along and across the leaf blades, creating a distinctive net-like pattern. Older lesions continue to elongate along leaf veins, and often are surrounded by a yellow margin.
Issues caused by NFNB?
A severe infection of NFNB may cause premature leaf death and reduce the seed weight. It may also reduce the number of heads and the number of grains per head.
Where does the NFNB come from?
Initial crop infection (primary inoculum) typically comes from infected stubble, on which the pathogen can survive for up to three years. The NFNB can also be seed-borne following humid conditions while the crop is maturing.
How do you control NFNB?
NFNB can be effectively controlled with the following strategies:
- Use resistant cultivars.
- Bury crop residue and destroy volunteers.
- Use balanced applications of nitrogen and phosphorus. Heavy nitrogen applications generally produce conditions favorable to outbreaks of this disease.
- Follow a crop rotation for at least two years with non-susceptible hosts. Barley should not follow barley, particularly if disease levels were high the previous year.
- If barley must be grown in two successive years, use a susceptible cultivar the first year and a resistant type the second.
- Use pathogen-free seed if possible.
- Use seed treated with a fungicide seed treatment.
- Application of a foliar fungicide can reduce the effects of the disease and keep your plants healthier.
In some circumstances you may not realize an economic return.
NFNB complete control is not economically feasible. There are three things that will help minimize the chance of infection:
- Removal of residue
- Crop rotation
- Use a fungicide seed treatment on your seed
A good practice is to always scout your fields for any type of diseases and disease pressure. For questions or recommendations contact your local barley agronomist.
McLean, Mark. “Net Blotches of Barley.” Net Blotches of Barley, Agriculture Victoria, June 2007, agriculture.vic.gov.au/agriculture/pests-diseases-and-weeds/plant-diseases/grains-pulses-and-cereals/net-blotches-of-barley. Updated: November 2017
Robertson, Larry D, and Jeffery C Stark. Idaho Spring Barley Production Guide. University of Idaho, 2003.
Skoglund, Leannea G. “Net Blotch (Barley).” Net Blotch (Barley), Center for Invasive Species and Ecosystem Health at the University of Georgia, 8 Apr. 2016, 16:38, wiki.bugwood.org/HPIPM:Net_blotch_(barley).