net blotch

Symptoms

Net-form: thin brown longitudinal + transverse stripes forming a netted pattern on leaf blade; spot-form: round to oval dark brown spots with yellow halo.

Plants affected

• barley

Easily confused with

• barley scald

  How to tell them apart: Net blotch shows one of two forms. The net form produces brown longitudinal and transverse streaks that cross-link into a dark-brown net or lattice pattern inside the lesion, surrounded by a yellow (chlorotic) halo. The spot form gives discrete dark-brown round-to-oval spots, each with a narrow chlorotic halo. Crucially, the dark reticulate (net) striping and/or the surrounding yellow halo distinguish it from scald's plain bleached centre. Favoured by warm, wet conditions and dense stands. Barley scald begins on the lower and mid-canopy leaves as oval to diamond-shaped lesions with a pale grey-green, water-soaked centre that dries to a bleached straw or pale-grey colour. The hallmark is a sharp, narrow dark-brown to reddish-brown margin ringing each blotch. Lesions stay flat (no netting, no spots inside), often run parallel to the leaf veins, and merge into large blotches in cool, wet, humid weather. No black net-like pattern is ever present.

Common questions

How do I recognise net blotch on barley?

Net-form: thin brown longitudinal + transverse stripes forming a netted pattern on leaf blade; spot-form: round to oval dark brown spots with yellow halo.

Do I have to report net blotch?

No. net blotch is not a notifiable organism, so there is nothing to report to an authority. Treat it as a normal garden problem.

How is net blotch treated?

Mainly with biological and cultural measures — removing affected material, changing the conditions that favour it, and treating with agents approved in your country. The exact steps and their timing depend on the plant, the season and where you live: Dr. Phyto works them out in a free diagnosis.