Alberta Barley

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Net blotch and spot blotch

The net blotch pathogen overwinters on crop residue and releases spores in the spring. The fungus that causes the disease is seed-borne and can cause seedling blight. Net blotch initially causes small, brown spots to appear on the leaves, sheaths and glumes. These eventually expand into long, narrow, brown streaks striped with occasional dark brown lines across the lesions, in a pattern that resembles a net. The lesions may also be yellow along the edges. If the lesions merge, they are capable of killing entire leaves. There is also a spot form of net blotch that resembles spot blotch, but is still a type of net blotch. Losses caused by the disease are due to shrivelled seed and reduced seed yield, and infected grain may be rejected for malt purposes.

The spot blotch pathogen also overwinters on crop residue and produces spores, which can survive for long periods of time in the soil. Like net blotch, it can also be seed-borne. The disease thrives in warm, wet conditions. Spot blotch initially causes small, brown spots, which expand into dark brown blotches. Although very similar to net blotch, spot blotch is caused by the same fungus that causes common root rot. Losses caused by the disease are due to shrivelled seed and reduced seed set.

Prevention/management tips:

Net Blotch

  • Allow several years between barley crops.
  • Use resistant varieties—six-row lines tend to be more resistant than two-row
  • Burying crop residue may reduce disease incidence
  • Monitor crops closely around flag leaf emergence and spray only if small spots have appeared on the upper leaves. In this case, foliar fungicides can reduce losses.

Spot Blotch

  • Monitor crops closely around flag leaf emergence and spray only if small spots have appeared on the upper leaves. In this case, foliar fungicides can reduce losses.