Scald
(Rhynchosporium secalis)

Overview

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Scald is an important fungal disease caused by the pathogen Rhynchosporium secalis. The disease is common to all cereal growing regions of Canada and other countries. In instances of severe infection, yield losses greater than 20% have been recorded.  Attacks occurring at the late boot or early heading stage reduce the size of the grain and the number of kernels formed per head. As such, the control and prevention of this disease are critical to reduce yield losses.

Main description

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The disease is favored by cool (12-14ºC), humid weather and dense crop canopies, where leaves remain wet for prolonged periods (free water present). Scalds distinct lesions have an obvious oval shape which develops on leaves and leaf sheaths. Initially, lesions are watery with a bluish-green colour. As the mature, they dry out and become tan in color. Lesions mature and coalesce to form blotches.

The fungus overwinters in the field on barley residue. Severe infections can occur where barley is grown continuously or under very tight rotations.

Scouting

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At the milky ripe stage, examine and assess a minimum of 25 main tillers selected randomly per plot. Check the level of infection on the first and second leaves of individual plants. Take the average of first and second leaves and determine the estimated yield loss using the following formula: % yield loss = 2/3 x % area of flag leaf infected + 1/2 x % area of second leaf infected / 2.