Seedlings may die before or soon after emergence even though they only show slight damage. Common root rot and crown damage lower yields. Infected plants tend to produce fewer tillers with smaller and fewer seeds per head. Some plants may ripen prematurely. Root rot in wheat and barley in Alberta causes average annual yield losses of 6 and 10 per cent, respectively.
Cereal crops can withstand a certain amount of seedling blight.
The extra space, water, nutrients and light that would have been used by missing seedlings are taken up by neighboring plants to produce more tillers with larger heads and kernels compensating for the loss. No definite threshold levels are available. The presence and severity of C. sativus on common wheat can be determined by pulling up plants and examining the crowns and subcrown internodes for disease. This gives an estimated yield loss as a percentage. The percentage of plants in the second group is the rating.