The takeaway: use protein bait in spring and early summer, switch to sweet in late summer and fall. When I matched the season the wasps emptied the station in a day; when I didn't, it sat untouched.
Early summer: protein won, easily
In June I put protein bait on one station and sweet on another, side by side. The protein station had a line within an hour. The sweet one barely got a visitor. The colony was raising brood and the workers were hunting protein for the larvae — so that's what they took.
Late summer: the switch flipped it
By mid-August the exact same setup reversed. Sweet bait got mobbed; protein went quiet.
Nothing changed but the calendar and the colony's appetite. With the brood matured, the workers were foraging carbohydrates for their own energy — the same reason they suddenly crash every picnic in late summer. Sweet bait was the obvious winner the rest of the season.
How I knew when to switch
I watched the wasps, not the date. When they started mobbing my soda instead of the grill, I switched to sweet.
That behavior cue beat any calendar rule. If they're working a meaty smell, run protein; if they're after your drink and fruit, run sweet. The science behind the seasonal switch is laid out well over at WaspBait — my test just matched what they describe.
Key takeaway
Don't argue protein vs. sweet — schedule it. Protein early, sweet late, and let the wasps confirm the switch.
See the full 6-method ranking →FAQ
Should I use protein or sweet bait for yellow jackets?
Both, at different times. The wasps mobbed protein in early summer when the colony fed larvae, then switched to sweet in late summer when workers wanted carbs. Match the bait to the season and they take it fast.
When do yellow jackets switch from protein to sweet?
In my yard, mid-to-late summer. Watch behavior, not the calendar: when they start mobbing soda and fruit instead of meat, they're in carbohydrate mode and sweet bait wins.