Cranberry research aims for longer shelf life

cranberries-closeup-100x80pMOUNT VERNON, Wash. – The cranberry season could extend beyond the fall and winter holidays thanks to the work of a new adjunct professor at Washington State University Mount Vernon.

Frank Caruso recently retired after 28 years at the University of Massachusetts Cranberry Station. He is conducting disease research for the Washington cranberry industry in hopes of giving the fruit a longer shelf life.

Cranberries are a $385.5-million-per-year industry in the U.S.

“Some growers can lose up to 30 percent of their crop” to rot, which is most often caused by fungi, Caruso said. “That’s a significant loss. The ultimate goal of my research here is to help growers reduce that percentage of fruit loss.”

Frank Caruso sorts through cranberry samples for signs of fruit rot, which can reduce a grower’s crop yield. (Photo by Kim Binczewski, WSU)

He is studying which fungi species are contributing to rot in the field and in storage. Cranberry samples are sent to him at regular intervals from six southwest Washington beds – three for berries sold fresh and three for those sold for canning. He follows the progression of fungi found in the berries throughout their development and ripening, from August through November.

“What I’m finding so far are significant differences in fungal populations in all six beds,” he said. “One fungus I’m finding a lot of, that is not a major player on the East Coast, is Colletotrichum acutatum, which is a major pathogen of numerous fruit crops.”

Once the fungi are identified, Caruso will correlate his findings with growers’ fungicide applications. This will help determine what changes are needed to reduce loss due to rot in the crop.

“We know that Abound fungicide works well on Colletotrichum acutatum,” he said. “But there’s another strain – or perhaps a different species – that I’m having analyzed right now; I’m finding it at higher levels in the fresh fruit beds.

“I don’t know what significance it has in these circumstances,” he said, “so the next steps will be to identify, isolate, inoculate and prove if it causes fruit-rot disease. Then the growers will be able to make choices on how to best respond.”

Fresh-fruit cranberries typically have less rot, he said, because more fungicides are applied at higher rates to extend storage life through the holiday season. More rot is found in process-fruit berries treated with fewer fungicides applied at lower rates because they will be stored frozen.

Caruso’s work is funded through a one-year grant, which could extend into a multiyear project, from the nonprofit Cranberry Institute and Ocean Spray food company. He is based at WSU’s Northwestern Washington Research and Extension Center vegetable pathology laboratory under the direction of Debbie Inglis.

He collaborates and shares lab space with other researchers at various facilities, including the WSU Long Beach Research and Extension Unit where he works with Kim Patten.



Frank Caruso, WSU Mount Vernon NWREC, 774-238-0698,

Debbie Inglis, WSU Mount Vernon NWREC, 360-848-6134,