Figure 3. Cross-resistance among flumorph, dimethomorph and iprovalicarb.

Log-transformed EC₅₀ values (the effective concentration for causing 50% inhibition of mycelial growth inhibition of Phytophthora melonis) for isolates of P. melonis were compared among the three carboxylic acid amide fungicides using Spearman’s rank correlation coefficients. (A), (B), and (C) indicate positive cross-resistance among flumorph, dimethomorph, and iprovalicarb; (D-F) include only the higher EC₅₀ values from (A-C), i.e., EC₅₀ values from CAA-resistant isolates. (D) reveals a positive correlation between the EC₅₀ values for dimethomorph and flumorph among CAA-resistant isolates, while (E) and (F) reveals a negative correlation between iprovalicarb and flumorph and between iprovalicarb and dimethomorph among CAA-resistant isolates.