Do I need to leave the house for a roach treatment?
Usually not. Gel baits and crack-and-crevice treatment don't require you to leave, and we'll tell you before the appointment if anything about your job is different.
Why do roaches come back after spraying?
Reviewed by William "Willy" Vizcarrondo, NYS Certified Pesticide Applicator (C1825832). Updated September 23, 2026.
Short answer
Because sprays only reach the adults out in the open. German cockroach nymphs in their first stage never leave the wall voids and the spaces behind appliances to feed, egg cases aren't affected by sprays, and the population rebuilds from them within weeks. Gel bait works because the roaches carry it back to the ones you can't see.
What the spray misses
The University of Florida's research on German cockroaches is direct about it: first-stage nymphs do not leave their harborages to feed, so baseboard sprays and foggers never touch them. They survive by eating the droppings of the adults, and a female's egg case holds 30 to 40 eggs. Spray the kitchen on Monday, and by the following month the nymphs have matured and the egg cases have hatched. It looks like the roaches came back. They never left.
Why bait works
German cockroaches eat each other's droppings, vomit, and dead, and gel baits use that. A roach eats the bait, returns to the harborage, and the bait moves through the colony by what the researchers call secondary transfer (UF/IFAS). The nymphs that never came out for the spray get it from the adults that did. Combined with an insect growth regulator that stops nymphs from maturing, that's what clears a kitchen for good instead of for a month.
On Long Island
Most of the roach calls we get in Nassau and Suffolk are apartments, two-family homes, and condos in places like Glen Cove, Great Neck, Hempstead, and Huntington Station, and the other reason they come back there is shared walls. German roaches move between units through plumbing chases. Treating one unit in a building where the neighbors have them is a short-term fix no matter what product is used, and we'll tell you that up front.
Related
Related questions
How long does it take to get rid of German cockroaches?
You'll see fewer within days and the population collapses over two to four weeks as the bait moves through the colony and the growth regulator stops the nymphs. The 60-day guarantee covers a return visit if they persist.
Can German cockroaches come in from outside?
No. They live only indoors with people and arrive in boxes, bags, used appliances, or through shared walls.
Sources
Still not sure? Call (516) 509-6001 and we'll tell you what you're dealing with.