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Wasp Nest Removal

Why Are Wasps Aggressive in September?

Wasps become aggressive in September because the colony stops raising young, which cuts off the sugary reward the workers were being paid in. Thousands of them are suddenly redundant, hungry and drawn to anything sweet, including your drink.

Dealing with wasps right now? Wasp Nest Removal, by a team that does nothing else.

The change people notice every September is real, and it is not your imagination that the same insect that ignored you in June will not leave you alone in September. The reason is a shift inside the nest rather than anything you have done.

The deal that breaks down

For most of the summer a worker wasp is a courier. It hunts insects, takes them back to the nest and feeds them to the larvae. It cannot digest that protein itself. What it gets in return is a drop of sugary liquid produced by the larvae, and that exchange is the only reliable sugar supply a worker has.

By late August or early September the queen stops laying. The last larvae pupate, the exchange ends, and several thousand workers are left with no job and no sugar. They do not simply die at that point. They go looking, and they are no longer tied to a feeding schedule.

That is the wasp at your picnic. It is not being territorial or defending anything. It is a redundant worker searching for the sugar it has lost, which is why it fixates on jam, fruit, fizzy drinks and beer rather than the meat it would have taken in July.

Why they seem bolder and clumsier

  • Fermenting fruit. Windfall apples and overripe plums ferment on the ground, and wasps feeding on them take in alcohol. A wasp that has been at the windfalls is noticeably slower, less coordinated and less inclined to move away when you wave at it.
  • Nothing left to lose. A worker in September has no brood to return to. There is no behavioural brake on persistence.
  • Numbers. The colony is at its largest of the year at exactly the point the workers become free-ranging, so you are meeting far more of them than you were in June.
  • Competition. Several wasps arriving at the same sugar source will jostle each other, and that agitation carries over to anything nearby, including you.

Does it mean there is a nest nearby?

Not necessarily. A foraging wasp will travel a few hundred metres from its nest, so wasps around your table in September could be coming from a nest well outside your boundary. What does suggest a nest on your property is a steady two-way traffic line: wasps arriving and leaving along the same route, in and out of one point in a roof, wall or bank, rather than drifting in from all directions.

If you can see that traffic, the nest is worth dealing with rather than waiting out, particularly if the entry point is near a door, a bin store or anywhere children play. See wasp nest removal for what a treatment involves.

Reducing the nuisance while the season runs

None of this removes a nest, but it does make September more bearable:

  • Clear windfall fruit rather than leaving it to ferment.
  • Keep bins closed and rinse anything sugary before it goes in.
  • Cover drinks outdoors and check the glass before you drink, because a wasp in a can is how most sting-to-the-mouth injuries happen.
  • Move away calmly rather than swatting. Crushing a wasp releases an alarm signal that draws others.

If you are stung and want to know what is normal and what is not, see wasp sting treatment, and are wasps dangerous for the risk picture.

How long it lasts

The behaviour eases once the cold arrives and the workers die off, which is usually through late autumn depending on the weather where you are. For the full cycle, see when wasps die off and when wasps are most active.

Frequently asked questions

Why are wasps so aggressive in September?
The colony stops raising young in late summer, which ends the exchange where workers fed larvae protein and received sugary liquid in return. Thousands of workers lose both their job and their sugar supply at once, so they go looking for it elsewhere. That search is what brings them to food, drink and bins.
Are wasps drunk in September?
In effect, some are. Windfall fruit ferments on the ground and wasps feeding on it take in alcohol, which leaves them slower and less coordinated. It is part of why they seem clumsier and less willing to move away late in the season.
Does a wasp problem in September mean a nest on my property?
Not always. Foraging wasps travel a few hundred metres, so they may be nesting elsewhere. What points to a nest on your property is steady two-way traffic in and out of a single point, such as a gap in the roof line or an air brick, rather than wasps arriving from every direction.
Will killing the wasps around my food help?
It tends to make things worse. A crushed wasp releases an alarm signal that attracts others nearby, so swatting often increases the number of wasps around you. Moving away calmly and removing the sugar source works better.
When will they stop?
The workers die off as the weather turns cold through late autumn, and the behaviour eases with them. Only next year's queens survive the winter, and they do not forage, so the nuisance ends with the first sustained cold spell rather than gradually through the autumn.