In the May 6 issue of the ICM newsletter, I had an article on resistance of Phytophthora to the fungicide metalaxyl. I discussed a possible treatment option if resistance occurs, which involved switching to a different seed treatment, such as mefenoxam. Alternating different fungicides is a common strategy in fungicide resistance management; however, experts in fungicide chemistry pointed out that the active ingredients of mefenoxam and metalaxyl are isomers. Isomers are compounds that have the same number of atoms but differ in their structural arrangement.