Autumn Pests: What Changes in September and October

September

Wasps Are Worst Just Before They Finish

The most counter-intuitive thing about autumn is that wasps become more of a nuisance as the colony dies, not less.

Through the summer the workers forage protein for the larvae, and the larvae reward them with a sugary secretion. In late summer the queen stops laying, the brood is reared out, and that internal supply of sugar simply stops. The workers — thousands of them, with nothing left to do — go looking for sugar outside. Hence the windfall apples, the bins, the pub garden, the tin of lager, and the general impression that the wasps have become bad-tempered.

They have not changed temperament. They have changed diet, and there are more of them than at any other point in the year.

A nest treated in September is still worth treating if it is causing a problem. Left alone it will die out by November, but that is six weeks away and the workers are active now.

Photographs on this page are for illustration purposes only.

September into October

Spiders, and What Is Really Happening

Every autumn brings a wave of large house spiders and the belief that they are coming in from the cold. They are not, particularly. What you are seeing is mature males walking about looking for females, which is why they turn up in the middle of a floor or in a bath rather than sitting in a web.

They are harmless and the season is short. They are worth mentioning here mainly because a lot of people reach for a spray in September for something that resolves itself in a few weeks.

October

The Handover

This is the one that matters. As the ground gets cold and wet and outdoor food runs short, mice and rats start moving towards buildings.

It is not a dramatic migration. It is a few individuals finding a gap that has been there all year, and it is why the calls start in late October and peak after Christmas — because what came in during October has been breeding since.

Cluster flies also move in during October, gathering in lofts and roof voids to overwinter, often in south-facing corners and often in large numbers. They do no damage and you will not see them again until the first warm day of the new year.

What to do about it

One Afternoon Outside

The autumn job is proofing, and it pays for itself more reliably than anything else on this site.

• Kneel down and go round the outside. Everything that matters is below knee height. Airbricks, the gap under an external door, where the waste pipe or the gas supply passes through the wall, the edge of the render, a missing air-brick grille.
• A mouse needs about a pencil width. Judge gaps against that, not against the size of a mouse.
• Close them with the right material. Wire wool packed tight, stainless mesh, mortar, or a metal plate. Foam and filler are chewed through in days.
• Move bird feeding away from the house. Winter feeding is good for birds and good for rodents. Keep it, move it, and sweep up underneath.
• Deal with the bin store and the compost now, while it is still dry enough to move things.
• Check the loft while it is light. If something is already up there, you want to know in October rather than in January.

Short answers

Questions, Briefly

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