Net Blotch

The net form produces fine, dark brown longitudinal and transverse streaks that form a net-like pattern within a yellowing zone, giving the disease its name. The spot form instead produces dark brown, round to oval spots surrounded by a chlorotic halo. In both forms, heavy infection leads to extensive leaf browning and premature death of foliage.

Pyrenophora teres survives between seasons on infected barley residue and can also be carried on seed. From residue it produces ascospores that infect emerging crops, while conidia formed on lesions spread by wind and rain within the crop. Under cool, wet conditions the disease can cycle repeatedly and move up the canopy over the season.

• Infected barley residue and volunteer plants carry the fungus over
• Infected seed can introduce the pathogen into new crops
• Ascospores from residue start infection, then conidia spread it further
• Cool, wet weather drives repeating cycles up the canopy

Barley is the main host of net blotch. Continuous barley cropping, retained infected residue, and use of infected seed all raise inoculum levels, while cool to mild, wet weather with long periods of leaf wetness favours infection and spread. Susceptible varieties allow the disease to build most rapidly.

• Barley-after-barley cropping with infected residue retained
• Cool to mild temperatures with wet, humid conditions
• Use of infected or untreated seed from an affected crop
• Susceptible varieties and dense canopies that hold moisture

Net blotch is managed by combining resistant varieties with practices that reduce residue-borne and seed-borne inoculum. No single tactic is sufficient in a wet season, so an integrated approach gives the most reliable protection.

• Grow varieties with good resistance to the net-blotch form present locally
• Use clean, tested seed to avoid introducing the pathogen
• Rotate away from barley and manage residue to lower carry-over inoculum
• Avoid overly dense canopies that keep leaves wet
• Monitor crops during cool, wet weather from early growth onward