September Pest Forecast: UK Pest Activity & Prevention Tips

Monday 24/08/2026

It has been a long, hot summer, with record-breaking temperatures and below-average rainfall across the UK. As we head into September, the seasons are changing and so is pest activity.

For pest professionals, this is a month of transition. Rodents start looking for shelter, bird-proofing projects pick-up, and overwintering insects start searching for somewhere to spend the colder months.

Here's how to stay ahead.

Birds

September marks the return of bird-proofing.

Breeding season is ending, and many sites that couldn't be worked on over the summer are now becoming accessible. Before starting any installation, check that nests are no longer active and that all birds have successfully fledged.

If you still have surveys to finish, now is the time to complete them. Finalise quotes, get customer approval, and book October installations while the weather is still good.

Whether it's bird spikes for ledges, solar panel proofing to prevent nesting beneath panels, bird netting for larger structures or bird alert systems and lasers for commercial sites, September is all about turning planned projects into confirmed work.

Cluster Flies

If there's one pest that likes to test your patience, it's the cluster fly.

September is when they begin searching for sheltered places to overwinter, disappearing into lofts, wall voids and roof spaces through the smallest gaps. Unfortunately, stopping them from getting inside isn't always possible.

Once cluster flies have settled into hard-to-reach spaces, they are also hard to treat. That's why acting early is so important. Smoke generators can help treat closed spaces where flies hide, while electric fly killers (EFKs) are useful for controlling the adult flies that come indoors.

One final tip? Set customer expectations early. Even after treatment, it's not unusual for hidden flies to continue emerging.

Rodents

Rodents don't wait for winter.
As soon as the nights get cooler, mice and rats start looking for steady food and warm places to live. Those small gaps around pipes, air bricks, and loading areas that were ignored during summer suddenly become very inviting.

September is one of the best times of the year to proof a building before rodents move indoors in greater numbers.

Check around the building before the rodents do. Fit covers on air bricks, seal entry points with rodent wool or mesh, and don't forget smaller gaps that need a good rodent-proof sealant. A little prevention now can save your customers a much bigger problem later.

Wasps

Just because summer is ending doesn't mean wasp season is over. In fact, September is often when customers notice them the most.

The reason is simple. By now, the queen has stopped laying eggs, so there are no new larvae producing the sugary secretions that normally feed the adult workers. With their main food source gone, the workers head off in search of sugar elsewhere.

That's why wasps suddenly become regular visitors to bins, cafés, beer gardens and outdoor seating areas.

Keep checking for active nests, especially where they could be a danger to customers or staff, and use wasp traps in high-activity areas to help reduce nuisance wasps while colonies naturally begin to decline.

Spiders

Every September, the same question comes up: Why are there suddenly so many spiders?
The answer is that there probably aren't.

September is mating season for many of the UK's house spiders. Males leave their hiding spots in search of females, making them more visible than they have been all year. It's not a spider explosion; they're just finally being seen.

For pest professionals, spider jobs are often as much about reassurance as treatment. Removing webs, reducing flying insects around a property and sealing entry points can all help reduce activity.

Looking Ahead

September is about getting ahead of the season. A few preventative measures now can make all the difference in the months ahead.
If you'd like advice on the best products for the job, the PestFix team is always on hand to help.