When are yellowjackets worst in Sacramento?
Yellowjackets are usually worst from late summer into fall. UC IPM says colonies grow through summer, are largest and most defensive late in the season when natural food is scarcer, and scavenge at picnics, garbage cans, pet food and ripe fruit before the colony declines in late fall.
Sacramento's rainless stretch lines up with that curve. June to September see little or no rain, and by September the yard has little else for a wasp to eat but what you leave out. That is why a lawn that felt safe in June can feel hostile by Labor Day.
Queens start new nests every spring, so April and May are the quiet window when a nest is small and easiest to deal with. If you see a lone large wasp prospecting along a fence line in spring, that is the colony beginning.
Is this the same as the mosquito district's yellow-jacket control?
No. The Sacramento-Yolo Mosquito and Vector Control District is a public agency, and according to Sacramento LAFCo its yellow-jacket control runs July through September. Sacramento Pest Control is a separate private call line that connects you with a local pest technician and is not affiliated with that district.
The district's roots go back to 1946, when it was formed as the Sacramento County-Yolo County Mosquito Abatement District, and it was renamed in 1990 to reflect added work on ticks, yellow jackets and other pests. Its public service can be a good first call for some situations. A private technician is the better fit when the nest is in a structure, outside that window, or you want a written report and a set time.
Our guide on how the district differs from a pest company lays out which service covers what, and the late-summer yellowjacket guide explains how the colony cycle works.
Why do yellowjackets chase me when I mow near a ground nest?
Mower vibration and engine noise near a ground entrance can be read by the colony as an attack on the nest. Guard wasps pour out and may sting repeatedly. If you find a nest by accident, walk away from it in a straight line, not toward the house door through the swarm, and call for treatment.
The entrance of a ground nest is easy to miss, especially in dry grass, under ivy or at the base of a slope. If you spot a steady stream of wasps at one hole, mark it from a safe distance with a stake or flag so the technician can find it quickly, and keep children and pets away from that corner.
Can I plug the hole or spray the nest myself?
It is safer not to. Blocking an active nest entrance can push wasps through drywall or light fixtures into the living space, and spraying a ground nest tends to provoke the colony. A technician uses label-directed products, protective gear and the right approach for the nest location.
Store-bought foam sprays and flooding with a hose are common mistakes. They agitate the colony, rarely reach the queen and brood, and are a leading way people end up with multiple stings.
