Cockroach Killer Sprays

The sprays in this range are formulated for fast knockdown on the cockroaches they are applied to, and some also leave a residual film that keeps working on treated surfaces. Check what the label states for the one you buy - knockdown and residual are different jobs, and not every spray does both.

Where cockroaches shelter, not across open floor. Treat cracks and crevices, behind and underneath the fridge and cooker, around motor housings, behind kickboards, around pipework under sinks and along skirting edges. Spraying where you saw one walk does very little if the harbourage behind the appliance is untouched. Use cockroach bait traps first to find which areas are active.

Only as often as the label directs. Reapplying more frequently than stated is not more effective and takes the product outside its approved use. In practice that usually means an initial treatment and a repeat if activity continues. You will also need to re-treat a surface after washing it down, since cleaning removes a residual film.

These are insecticides and need treating as such. Keep children and pets out of the room during application and until treated surfaces are completely dry, ventilate while you work, and do not spray food-preparation surfaces or utensils unless the label specifically allows it. Cover fish tanks and move pet bowls and bedding out before you start. If you would rather avoid a spray in an occupied room, enclosed bait traps keep the active substance contained.

The two usual patterns look different. If you knocked cockroaches down and more appeared within days, the harbourage was never reached - treat behind and under appliances, in motor housings and around pipework rather than the open room. If nothing changed at all, you are probably not treating where activity is: put traps out for a few nights and let those tell you which corner to work on. Either way, allow for the egg cases, which survive most treatments, so a repeat application in line with the label is normal rather than a sign the product failed.

Yes, but not on the same spot. Spraying over or next to gel bait can put cockroaches off feeding, and feeding is what reaches the ones you never see. Bait the harbourages, spray the routes and cracks around them, and keep monitoring traps running so you can see whether numbers are actually falling. Read our guide to getting rid of cockroaches yourself for the order to work in.

If activity is still there after a full treatment cycle in line with the label, if it has spread beyond one room, or if you are in a flat or shared building where the source may be next door. German cockroach infestations are hard to clear as a DIY job. Look for a qualified pest controller with BPCA membership.