Chang-Lin Xiao recommends that use of Penbotec and Scholar alternate from year to year to preserve their effectiveness against fungal pathogens like this blue mold on a Gala apple. Chang-Lin Xiao Resistance of the blue mold pathogen to the postharvest fungicide Penbotec (pyrimethanil) was seen in Washington State within five years of the product being introduced, illustrating the need to use resistance management ­practices. Washington State University postharvest scientists observed resistance of blue mold (Penicillium expansum) to Penbotec for the first time in 2009 at a packing house where it had been used as a postharvest drench for apples annually […]