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Yellowjackets at picnics and fallen fruit in fall

September to October

Yellowjacket colonies peak in size in late summer, and late in the season the workers forage mostly for sugar instead of the insect protein they hunted earlier in the year. That sends them crowding picnics, fallen fruit, soda cans and trash cans through September and into October, right up until the first hard frost kills the colony.

Why this time of year

Eastern Massachusetts colonies peak around Labor Day, and from then until the first hard frost the workers forage mostly for sugar, which is when they crowd picnics, fallen fruit and trash cans.

How to notice it

  1. Look at open trash cans, recycling bins and compost piles for wasps clustering on sweet residue.
  2. Check under apple, pear or other fruit trees for yellowjackets feeding on fallen, overripe fruit.
  3. Look inside any soda can or cup left outside before anyone drinks from it.
  4. If a yellowjacket lands on a picnic plate, stay still, do not swat, and let it leave on its own.

Try this with kids: Can you find a yellowjacket checking out a soda can, a trash can or a fallen apple? What do you think it is looking for now that summer is ending?

a colony is the whole wasp nest, thousands of sterile female workers built and defended around one egg laying queen

Safety

  • Yellowjackets are drawn to sugary drinks and will crawl inside cans and cups, so check before you sip outdoors in late summer and fall.
  • Stay still and do not swat at a yellowjacket investigating your food; wait for it to fly off, then cover, finish or remove the food.
  • Stings can cause serious allergic reactions in some people; anyone with a known allergy to wasp, bee or hornet stings should carry their prescribed medication, and have any nest on the property removed by a professional rather than handling it themselves.

Sources

  • umass.eduUMass Extension: conflicts rise in fall (August through September) as colonies peak; yellowjackets forage primarily for sugar at the end of the season; they cease with the first hard frost, which kills all workers; only a mated queen overwinters; soft drinks attract them; do-not-swat and allergy advice.
  • extension.psu.eduPenn State Extension: eastern yellowjacket annual cycle, queens start nests May-June, males and new queens produced August/September, fertilized queens overwinter.
  • extension.psu.eduPenn State Extension: German yellowjacket nests reach 1,000-3,000 workers by fall, then decline until workers die off with declining food and cold weather.
  • homegarden.cahnr.uconn.eduUConn Home and Garden Education Center: late August/early September peak; wasps seek sweet sugary energy as floral resources become scarce; soda-can example; workers die out with colder weather while the queen overwinters.
  • cals.cornell.eduCornell IPM: colonies can grow to 5,000 workers or more by end of summer; predatory and scavenger foraging; later-summer activity around picnic foods, drinks, trash and compost.

Checked against these sources on September 28, 2026.

In the guide for September, October

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