Summary: Blue mold is one of the major causes of loss to decay in the Washington apple industry. Penicillium expansum Link and P. so/itum Westling are the major causal agents for blue mold on pome fruit in the Northwest (Sanderson & Spotts, 1995). Currently, only thiabendazole (TBZ) and captan are registered for postharvest use against this disease. Many fruit packers are hesitant to use captan, because it is not accepted in some important overseas markets. Recently we found that 30% of isolates of P. expansum recovered from DPA drenches were insensitive to TBZ. In the Mid-Columbia area, up to 50% of isolates of P. expansum recovered from fruit and dump tanks in the mid 1970's were benomyl-tolerant (Bertrand & Saulie-Carter, 1978). Although some biological fungicides are being developed for postharvest use, those currently registered are not very effective. With the new Food Quality Protection Act, new chemical fungicides are unlikely to be registered for postharvest use.
