(A,B) Assays for cellular sensitivity of the strains carrying a single Nox gene mutation (ΔnoxA, ΔnoxB and ΔnoxR), the rescued strains (CpB24 and CpR40) and the NoxA NoxB (ΔnoxAB) and NoxA NoxR (ΔnoxAR) double‐mutant strains of Alternaria alternata to the cell wall‐targeting compounds sodium dodecylsulphate (SDS), calcofluor white (CFW) and Congo red (CR), as well as vinclozolin and fludioxonil fungicides. Fungal strains were grown on potato dextrose agar (PDA) amended with or without chemicals for 5 days. Two independent mutant strains of each type were used for the assays. The percentage change in radial growth was calculated as the percentage of growth of the deletion mutants in relation to the wild‐type grown on the same plate. A negative percentage change indicates growth reduction in relation to the wild‐type. A positive percentage change indicates that the mutants grew more rapidly than the wild‐type. The data presented are the means and standard errors of two independent mutants with at least two replicates of two experiments (n = 8). For each test compound, means indicated by the same letter within a test compound are not significantly different from one another, P < 0.05.