It’s a supposed to be a high of 90°F on a late-July day, and cherry growers in the Kelowna, BC, area are nervous. Heat like this might exacerbate a new cherry disorder called slip-skin, where a cherry’s outer skin detaches from its inner flesh, typically toward the shoulders and tops of the fruit. The slip-skin area then ferments and rots.
On this warm day, I’m riding around the Kelowna area with Molly Thurston, a Field Service Horticulturalist with BC Tree Fruits, as she monitors cherry orchards in her area. It is Thurston who helps growers walk that fine line between Brix and softening shoulders, believed to be a precursor to slip-skin. If a grower waits too long, the entire crop could be rejected at the packing plant.
There are a lot of unknowns about the disorder that started showing up in 2012. It’s believed to have something to do with the rising temperatures in the area, especially right around harvest. There’s also belief that there’s some fungal pathogen that could be a cause, as it’s been found in the damaged tissue of cherries with slip-skin. It seems to be a varietal issue, showing up in ‘Stacatto’ and ‘Sweetheart.’
That’s the fascinating thing about this ride-along. I couldn’t help but wonder: What to do when preventing slip-skin isn’t on the table? I’d like to think that fruit growing is as much about reacting to the current growing conditions as it is about prevention. Molly tells me conventional fungicide and potassium bicarbonate sprays haven’t really made a difference in the incidence of slip-skin.
Some relief may come with better cropload management, summer shoot thinning, or even applications of sunburn protection. For now, all growers can do is scout for early indications of slip-skin and, if discovered, harvest the crop as quickly as possible.
I didn’t realize all that went into working as a field service technician. Especially after we stop at one grower’s orchard to check for slip-skin. To say he’s nervous is an understatement. He tells me he lost his entire crop last year to the mysterious malady. Molly is joined by two more field service technicians at the farm to check on the progress of the cherry crop. Samples are taken from a few trees, the team sorts fruit by size and color, and Brix is assessed.
The Brix wasn’t off the charts, but some of the cherries had softening shoulders. So, Molly suggested the grower begin picking the tops of his trees in three days to account for the preharvest interval of his last spray. The hope is that the cherries most at risk would be picked first.
Molly was hopeful this year that the grower wouldn’t lose his crop to slip-skin again, but as she drove off, she suspected her days would only get busier. More heat was in the forecast, and ‘Stacatto’ harvest was just picking up.