Good coverage underpins fungicide efficacy, but can be challenging in large biomass crops where sprays can struggle to penetrate down the canopy, says Hutchinsons agronomy innovation director, David Howard. The spectre of yellow rust is a big unknown this year given the changes to YR15 resistance, potentially bringing rust to the fore in more crops, beyond the usual higher risk eastern areas. “Coverage is particularly relevant for rust control, which as a sporulating disease with a short lifecycle, can rapidly reinfect up the crop from any inoculum on lower leaves,” he notes. This is unlike septoria, which is spread by…