The guide covers visual differences between net and spot form blotches, the diseases' life cycle and methods of spread, control options and emerging issues with fungicide resistance.

Net form net blotch (NFNB) and spot form net blotch (SFNB) are foliar diseases of barley which account for more than $125 million of annual losses in Australia.

The NSWDPI guide has plenty of details on blotch disease and how to manage it. Yield losses from NFNB generally range between 10-20 per cent, but losses of more than 30 per cent have been reported in susceptible varieties. NFNB most commonly causes losses during seasons with a yield potential (more than five tonnes per hectare), coupled with wet conditions during spring. Grain quality can also be affected.

Yield losses resulting from SFNB are generally less than 10 per cent but severe outbreaks can see losses of up to 40 per cent. Losses due to SFNB generally occur when infection severity is greater than 10 per cent on the top four leaves at grain fill stage.

When severe, SFNB can also cause significant reductions in grain plumpness. Increases in screenings and reduction in retention and grain weight can also occur.

Net blotch control options include grow resistant varieties, not planting seed from infected crops, crop rotation, reducing stubble loads, using seed dressings and using foliar fungicides.

The guide can be downloaded here: https://bit.ly/3rV8QFS