Jan 2, 2014Cranberry research seeks longer shelf life
A new adjunct professor at Washington State University (WSU) is trying to find ways to extend the cranberry season beyond the fall and winter holidays.
Frank Caruso recently retired after 28 years at the University of Massachusetts Cranberry Station. He is now 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 United States.
“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.”
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 moved to Edmonds, Wash., to be near both of his children and one grandchild.
Caruso’s work is funded through a one-year grant, which could extend into a multi-year 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.
“We decided to follow the progression of fruit infection by fungi in six beds. Three of these beds were located in the Long Beach area, and fruit in these beds were water harvested for their use as processed fruit,” Caruso said. “Three of these beds were located in the Grayland area, and fruit in these beds were dry harvested for their use as fresh fruit. All of the beds were planted with the cultivar Stevens.
“Kim’s assistant sampled fruit from these six beds in mid-August, early September and late September. The latter sample was a much larger sample than the previous two samples, as it was harvested one week prior to commercial harvest. Three samples were subsequently taken from this larger sample while the fruit was stored in the cooler. Consequently, there were three field rot samples and three storage rot samples. Healthy and rotted berries were both plated on culture media for the latter five samples. There was no rot present for the first sample from which only healthy berries were plated. Fungi were identified in the plates 21 days after fruit were plated.
“At this point, fungi have been identified from the first five samples; the sixth sample will be evaluated on Dec. 23. Results thus far have included fungi that are important pathogens in Massachusetts fruit, and other fungi that are more important pathogens in Washington fruit.
“Populations of these fungi have varied significantly among the six beds. This may be accountable to the different locations (Long Beach versus Grayland), the end fate of the fruit (processed versus fresh), the fungicide schedules, the strain of Stevens or other factors. When the production records are received from this growing season, as well as a history of the individual bed, some conclusions can be reached on why certain fungal pathogens are present at higher levels than others.
“One conclusion that I have already reached is that (unlike Massachusetts) a key fungus contributing to fruit rot in Washington is Colletotrichum acutatum. Growers will be urged to use the fungicides Abound and Evito in 2014. These fungicides are in the strobilurin class, and highly effective against colletotrichum. The use of these fungicides in Washington has been very limited thus far. The results of this study will be reported at the winter meeting of the Washington cranberry growers in January.
“This is only the first year of a multi-year study,” Caruso said. “It is always hard to make conclusions based on a single growing season. The study may be expanded in 2014 to include other beds, and possibly beds planted with other cultivars.”