We’ve had raspberries on our farm for decades and it was always a reliable source of mid-summer fruit. The variety we grew was, Boyne. This variety was released in 1960 and is an extremely winter hardy, early-season variety.
And we were happily picking—until the Spotted Wing Drosophila (SWD) fruit fly invaded our bliss. Native to Asia, SWD can now found in most of the primary fruit growing regions of the U.S.
According to North Dakota State University, “Unlike other vinegar flies that prefer to attack overripe and rotting fruit, the SWD will also lay its eggs in healthy, ripening fruits. Eggs hatch into small larvae (or maggots) and then larvae feed on the fruit, causing spoilage.”
The dreaded Spotted Wing Drosophila fly
We’ve experienced significant losses in our June bearing strawberry patch as early as the second picking.... before our summer bearing, Boyne raspberries even started to set fruit. And the SWD was there in high numbers by the time the raspberries started to ripen, causing significant losses—and we abandoned all hope of a harvest.
So David sought an earlier bearing raspberry variety that would beat the SWD’s reproduction cycle. We were introduced to the variety, 'Prelude' by Jim Walla, owner of Northern Tree Specialties. According to Jim, “The Prelude raspberry's claim to fame is that the floricane berries, those that are produced on the previous year's canes in early season, ripen earlier than any other cultivar.”
Prelude raspberries
David’s hope was to be able to at least harvest SOME raspberries before the SWD population built up too high. But despite Prelude’s earlier production than the Boyne raspberry, the SWD invasion still left us with too short a window to get much of a harvest.
David decided to manage them for fall production instead-- by cutting all the canes off in early spring so they would produce fruit in late summer to early fall. His strategy was to move the raspberry production window out of the SWD fly’s reproduction window and have less of population doing damage.
The results? When the Prelude raspberries first started to bear in August, there were still some SWD flies present but they quickly waned as the fruit production ramped up! We were able to get a successful harvest through September deep into October before killing frosts ended the run. David deemed it a real success!
I call that a real win! And I am a grateful beneficiary!!
Fall raspberry stash in the freezer!
Now to create a trellis system for these amazing canes!
One thing to make sure to note-- this works because the Prelude variety is early bearing. For later bearing raspberries, like Boyne, cutting all the canes back in the spring would likely push their fruiting season too far into the fall in our region. We'll be experimenting with that next season, so stay tuned!
Hope this helps you rethink how to beat the dreaded Spot Wing Drosophila fruit fly!
Your garden coach,
Theresa