Disease management of winter wheat with reduced doses of fungicides in Northern Ireland

Trials in Northern Ireland from 1994-2002 with a range of fungicides, applied at a range of doses to winter wheat, generally showed improved retention of green leaf area (GLA) due to good control of the principal pathogen Mycosphaerella graminicola. This led to significant increases in yield, thousand grain weight and profitability particularly when cultivars susceptible to M. graminicola were treated. Frequently, the maximum profitability was achieved with fungicides applied at 50% or less of the manufacturer's recommended dose. Overall profitability with cultivars resistant to M. graminicola was higher than with susceptible cultivars and treatment of resistant cultivars with fungicides did not significantly increase profitability any further. This indicates that, for cereal growers in N. Ireland, use of resistant cultivars should be the primary method of control of M. graminicola. A comparison of a spray programme at GS 32 and 39 compared with one with an extra spray at GS 59, showed tendencies towards improvement in GLA retention and yield with a susceptible cultivar, but none with a resistant. However, this was not statistically significant and with current grain prices would not have been translated into increased profitability. Results generally point to the importance in N. Ireland of using resistant cultivars and to applications at GS 32 and 39 if susceptible cultivars are grown.