Do cockroach foggers and bug bombs actually work?

One can, one afternoon, problem gone: it is easy to see the appeal, especially when you are worn out. But a fogger releases a mist that drifts down and settles on open surfaces: worktops, floors, the tops of cupboards. Cockroaches spend the day in cracks, behind kitchen units and inside walls, and their egg cases sit in the same places. The mist mostly misses them.

Why bug bombs fall short

• It lands on top, not inside. The mist settles on what faces up. It does not find its way into hinges, wall voids or the back of the fridge motor.
• It can drive them deeper. Like many sprays, it can repel the cockroaches it does not kill, so they retreat further into the walls.
• In flats, it moves them around. Cockroaches escape along pipes into the next flat, then drift back once the air clears. Your neighbour may get them for a while, and you get them again.
• It does not stop the next generation. Egg cases are hidden and protected, so young ones keep hatching after the fog is gone.
• It leaves residue. That means cleaning every food surface afterwards, and residue near bait puts cockroaches off eating it.

If you use one anyway

A fogger is a regulated pesticide. Follow the label exactly, and check it is allowed where you live. The label is the rule, and these are the points it usually covers:

1. Use only the amount the label gives for the size of the room. More is not better, and it raises the risk.
2. Turn off pilot lights, flames and anything that could spark, as the label directs.
3. Cover or remove food, dishes and utensils, and anything else the label lists.
4. Everyone out, people and pets, for the full time on the label.
5. Air the room before going back, then wash surfaces that touch food.

Kids, pets, pregnancy and asthma: everyone leaves for the full time on the label, including caged pets. Fish tanks and pet bedding need protecting as the label says. Never set off more than the label allows: the mist can catch fire near a flame or spark. If anyone feels unwell after exposure, see a doctor or pharmacist and take the label with you. Our page on safety and labels has more, and how long to stay out covers going back in.

What reaches them instead

There is no single big fix, but there is a short plan that goes where the fog cannot. For the small indoor German cockroach:

1. Starve them. Grease, crumbs, open food, the dripping tap.
2. Gel bait in small dots right in the hiding spots. Cockroaches carry it back to the ones you never see.
3. An insect growth regulator to stop the young from becoming breeding adults. This is the part that deals with the eggs a fogger cannot touch.
4. Monitor traps, counted weekly, so you know it is working.

Our answer on what to get and in what order lays it out. For the larger cockroaches that come up from drains, the first step is closing the way in, see four cockroaches side by side.

In a flat, bring the building in

If you live in a block, ask your landlord or building manager in writing to treat the flats around yours at the same time. Treating one flat alone tends to move cockroaches rather than end them. More in cockroaches coming from next door. Still catching young ones after four weeks of bait and a regulator? That is the point to call a professional.