Improving spring and summer fungicide treatments for winter barley

Abstract

The response of winter barley to broad-spectrum fungicides applied at first node stage [growth stage (GS) 31] or as two-spray programmes [first node stage and flag leaf to ear emergence (GS 39–59)] was examined at 22 sites over five years during 1986–1990. Single sprays were also applied at an intermediate timing [third node to flag leaf emerging (GS 33–37)] at all sites in 1989 and 1990. The mean response to the single spray at GS 30–31 was 0.86 t ha −1 but ranged from 0.25 to 3.03 t ha −1 (4–80%). With the addition of a late spray (GS 39–59) of propiconazole plus tridemorph to the spring treatment, mean response was 1.25 t ha −1 [range 0.35–3.32 t ha −1 (5–87%)]. There were some differences between fungicides and fungicide mixtures applied at GS 31 and a prochloraz component was needed for effective control of eyespot. Seasonal differences in the mean response to the GS 39–59 treatment reflected differences in disease pressure after GS 59. The GS 30–31 treatment failed to maintain disease control up to the milky ripe stage (GS 75) in years when disease pressure was high. Yield responses were correlated with disease severity on leaf 2 at the time of the spring (GS 31) application and with the degree of control of eyespot on the stem base and of foliar diseases on the flag leaf at GS 75. A single spray applied at GS 33–37 gave comparable yields to the two-spray programmes and has potential to improve profitability where disease levels are low at the first node stage.