Spotted-wing drosophila
A small fruit fly 2 to 3 mm long. Males have a single dark spot on each wingtip. Females have a serrated egg-laying tube that punctures unbroken ripening fruit, which sets SWD apart from vinegar flies that only feed on already-damaged fruit. Active from first ripening through frost.
Drupelets soften and collapse within a day of ripening. Tiny pinprick scars on the berry surface mark egg-laying sites. Cut a soft berry open and white maggots wriggle inside the drupelets. Fruit fermentes on the cane and the whole harvest can be lost within a week of the first picking.
Mesh netting on canes from green fruit through harvest
Drape fine insect mesh (~1 mm openings, ProtekNet or similar, ~$30 to $50) over the trellised canes once berries reach green-fruit stage and seal at the base. The mesh is fine enough to exclude SWD adults yet still lets light and rain through. The single most effective home defense for blackberry harvests.
Pick daily and refrigerate within an hour
Walk the row every morning once the first drupelets ripen. Pick every berry that gives to gentle pressure, even slightly soft ones.
Drop overripe or damaged fruit into a sealed bag in the trash, never on the ground or in the compost. Fallen fruit breeds the next generation.
Refrigerate harvested berries within an hour. Cold below 36F stops larval development inside any fruit that was already infested.
Apple cider vinegar traps to monitor populations
Fill a deli cup with 1 inch of apple cider vinegar plus a drop of dish soap. Punch 6 holes 3 mm wide near the top.
Hang one trap per 10 feet of canes at fruit height starting 2 weeks before the first ripe berries.
Check weekly. Tiny dark flies in the cup mean SWD pressure is on. Tighten netting and shorten harvest intervals when you see them.
