Most pest infestations do not announce themselves with a parade of insects across your kitchen counter. They start quietly — behind walls, under appliances, in attics and crawl spaces — and by the time you notice, the problem is often bigger than you think.
Knowing what to look for is the first step toward protecting your home. Here are the five most common signs that pests have moved in, what each one means, and when it is time to call a professional.
1. Droppings and Urine Trails
This is often the first sign homeowners notice. Pest droppings vary by species, and identifying them correctly helps determine what you are dealing with:
- Mouse droppings: Small, dark, rice-shaped pellets (about 1/4 inch). Found along baseboards, in drawers, behind appliances, and inside cabinets.
- Rat droppings: Larger (1/2 to 3/4 inch), blunt-ended, and often found near food sources and along travel paths.
- Cockroach droppings: Tiny, dark specks resembling ground coffee or black pepper. German roaches leave these in kitchen cabinets, under sinks, and around appliances.
- Termite frass: Tiny, wood-colored pellets found near baseboards or windowsills. This indicates drywood termites (less common in Missouri, but possible).
What to do: Do not sweep up droppings without protection — rodent droppings can carry hantavirus and other pathogens. Wear gloves, use a damp paper towel, and disinfect the area. Then call a professional to identify the species and assess the scope.
2. Gnaw Marks, Holes, and Structural Damage
Rodents gnaw constantly to keep their teeth trimmed. Look for chew marks on food packaging, wooden baseboards, electrical wiring, and PVC pipes. Fresh gnaw marks are lighter in color; older ones darken over time.
Other damage signs include small holes in walls or flooring (mice can squeeze through gaps as small as a dime), damaged insulation, and shredded paper or fabric (nesting material). Carpenter ants leave smooth, clean galleries inside wood — if you see sawdust-like debris (frass) piling up near wood structures, that is a serious red flag.
What to do: Gnaw damage to electrical wiring is a fire hazard. If you see chewed wires, address the pest problem and have an electrician inspect the wiring. For structural wood damage, get a professional pest inspection to rule out carpenter ants or termites.
3. Unusual Sounds — Especially at Night
Scratching, scurrying, or tapping sounds in walls, ceilings, or attics — particularly after dark — almost always indicate rodents, squirrels, raccoons, or bats. Mice and rats are most active between dusk and dawn. Squirrels, on the other hand, are daytime creatures, so scratching sounds in the attic during morning hours point to squirrels rather than rodents.
Clicking or rustling behind walls can also indicate a large cockroach or carpenter ant population.
What to do: Note the time and location of the sounds. This information helps your pest control technician narrow down the species and focus the inspection. Do not attempt to open walls or seal gaps until the pest has been identified — sealing an animal inside your home creates a much worse problem.
4. Property Damage and Unusual Odors
A musty, oily odor in enclosed spaces often indicates a rodent infestation. Mice and rats leave grease marks (rub marks) along surfaces they travel repeatedly. A strong, sweet smell in walls can indicate a dead animal. Cockroach infestations produce a distinct, unpleasant musty odor that becomes more noticeable as the population grows.
Other property damage to watch for: damaged garden plants (moles, voles, or grubs), holes in your yard (ground-nesting pests), and damaged outdoor furniture or deck wood.
What to do: Persistent unexplained odors warrant an inspection. If you suspect a dead animal in a wall or crawl space, a professional can locate and remove it safely.
5. Seeing Live Pests — Even Just One
Seeing a single cockroach, mouse, or ant does not always mean you have an infestation — but it often does. Pests are secretive by nature. When you see one in the open, especially during daytime, it usually means the population is large enough that individuals are being pushed out of hiding by competition for food and space.
This is especially true for German cockroaches and bed bugs. A single German roach sighting in a kitchen usually means dozens or hundreds more are hiding behind appliances, inside walls, and under countertops. One bed bug on a mattress seam means the infestation is already established.
What to do: Do not ignore a single sighting. It costs far less to address a small population now than a full infestation later.
DIY vs. Professional: When to Make the Call
For a single mouse that wandered in through an open garage, a snap trap may do the job. For a few ants near a window, a bait station from the hardware store might handle it. But for anything beyond a minor, isolated issue, professional treatment saves time, money, and frustration.
Call a professional when you see any of these situations:
- Droppings in multiple locations or recurring after cleanup
- Structural damage to wood, wiring, or insulation
- Sounds in walls or attics that persist for more than a day or two
- Any sign of termites — swarmers, mud tubes, or wood damage
- Cockroaches or bed bugs — DIY treatments almost always make these worse
- Wildlife in your attic, crawl space, or chimney
Roberts’ R.O.S. Bi-Monthly Program: Year-Round Protection
For homeowners who want to stop pest problems before they start, Roberts Pest Control offers the R.O.S. (Roberts Ongoing Service) bi-monthly program. A licensed technician visits your home every two months to apply preventive treatments, inspect for new activity, and address any emerging issues — all covered under a service guarantee.
Most pest problems we treat could have been prevented with a regular service plan. The R.O.S. program is designed to keep your home protected through every season, from spring termite swarms to winter rodent pressure.
Schedule Your Free Inspection
If you have noticed any of these signs in your St. Louis area home, do not wait for the problem to grow. Roberts Pest Control provides free, no-obligation inspections for homeowners across Jefferson County, St. Louis County, St. Charles County, and surrounding areas.