Yellow Jackets, a pain in the…Fall!
After spending the afternoon being "stalked" by an angry Yellow-Jacket at my remote, then coming home to 2 in my living room that wanted at me, I decided to do some research on why they can be so nasty the closer to fall we get. Here's here's what I found out...
Yellowjackets are at their pestiest in the late summer or early fall. There are no more developing larvae to feed so workers are foraging randomly for themselves. They can become increasingly aggressive in gathering food and are more likely to sting during this time. Also in the fall, their food interests switch from mainly proteins to mainly sweets. You'll find them buzzing around your soda can, which can mean a nasty surprise if your lips and yellowjacket meet.
In late summer, a yellowjacket colony is at its largest (1,000-4,000 workers), but its social structure is breaking down. The workers have built larger reproductive cells in which new queens have developed. Males are also produced in the late season colony. These reproductives leave the nest and mate and the newly fertilized queens will look for a protected site, such as under loose tree bark, to spend the winter.
Sometimes the overwintering queens will end up seeking shelter inside buildings. In almost all cases, the worker yellowjackets will die at the end of the season, along with the current colony queen.
So, how much longer will yellowjackets be active? It depends on your location. Overall, you can expect peak yellowjacket activity in late summer and early fall in most areas, and the yellowjackets' "pestiferous" activity may extend to late fall, always depending on the weather.
In more northern states, yellowjacket colonies begin to decline in July or August, but some colonies remain active and growing throughout September, which means you can still expect some yellowjacket activity in October. In southern states, reproductives may not even be produced until after September. In rare instances, foraging yellowjackets can be found as late as December, even in northern areas.
In the mountains, yellowjackets have been reported to burrow up through the snow from ground nests to forage for food! Yellowjackets nesting in protected building voids often remain active well into December.
...so there ya go, get ready for overly aggressive yellow-jackets for a while