Why do cockroaches come inside? Here’s how to keep them out of your Sacramento home

Cockroaches love the heat. As Sacramento residents gear up for summer, how can you keep these creepy crawlers right where you want them — away from your home?

These cold-blooded insects become more active in late spring and early summer as they generally thrive in warm and humid weather. The warmer it is, the more active they are, UC Davis entomologist Lynn Kimsey told The Sacramento Bee for a previous story.

There are several varieties of cockroaches that exist in California — and some of them like to come indoors.

Here’s why the pests are attracted to your home, and how to keep them out:

Why cockroaches enter homes

While there may be an idea that cockroaches swarm to houses that are not clean, that’s not usually the case. Bill Donahue, an entomologist and the owner of Sierra Research Laboratories Inc. in Modesto, said cockroaches are scavengers and have adapted to survive in many situations.

“I think people thought that if you get cockroaches, you must have a dirty house,” Donahue said.

While garbage and clutter don’t help the problem, Donahue said roaches are usually there in search of nutrients and water — not because your house is gross.

With an unusually wet winter and early spring, Donahue said the outdoor species’ behavior may change now that there’s more access to water sources, so you may see fewer around your home this season.

While cockroaches have a “yuck” factor, Donahue said that’s most of what residents have to worry about with the bug.

However, they can carry diseases that can be harmful to humans, including Salmonella and poliomyelitis, the virus that causes polio, according to the U.S. Centers for Disease Control and Prevention.

In general, cockroaches are a common source of allergens and can trigger asthma. They have also been known to “cause considerable psychologic or emotional distress” to some, the CDC states.

“People just don’t want them around,” Donahue said.

When should you worry about seeing a cockroach in your home?

They are generally nocturnal creatures, and if they’re spotted during the day, it is a sign of a robust population.

In California, there are eight exotic species of cockroaches. The species that is the main cause for concern in the state is the American cockroach because it can carry and spread bacteria. Restaurant inspectors look out for this as sign of filth.

These are the signs you have an American cockroach infestation, according to the National Pest Management Association, and you should call pest control:

• Droppings in dim areas of your home

• Presence of egg capsules, which are about 8 millimeters long and dark-colored

• A musty smell around

However, the ones most frequently spotted in California homes are the German, Oriental and Turkestan cockroaches.

The German cockroach is the most common indoor species — common in multi-unit housing — and they like food preparation areas, according to the UC Integrated Pest Management Program, which causes concern for contamination.

While seeing one or two might not be a cause for alarm, you don’t want an infestation and again: They can transmit disease.

How to control cockroaches within your home

Donahue said he tends to take an integrated approach when trying to control cockroaches, working with both traps and chemicals.

To prevent attracting cockroaches within the home, Donahue said reducing garbage and clutter can help.

“German cockroaches, especially, are pretty predictable,” Donahue said. “That’s where trapping becomes pretty effective.”

While effective, trapping requires patience, Donahue said. He said he’s been successful trapping roaches with something as simple as an empty 2-liter soda bottle.

Here’s how that trap works, according to cockroachfacts.com: Cut the top off the bottle, right where it rounds out to its full width. Rub petroleum jelly inside the top half of the bottle (and the bottleneck). Then, place some bait (like peanut butter, a piece of a banana peel or a similarly sweet bait) at the bottom of the bottle, slide the top section upside-down into the bottom section and wait for roaches to climb in after the bait.

Roaches are adaptable creatures, and outdoor varieties are best controlled by liquid chemicals as a perimeter treatment, Donahue said.

“Frankly, most people just want them gone immediately,” Donahue said. “At that point, we come to chemical control.”

Here are more tips, from the National Pest Management Association, to help keep cockroaches away from your home:

• Seal cracks in walls and gaps near electric sockets

• Keep counters, sinks, tables and floors free of clutter and crumbs

• Don’t let dishes pile up

• Avoid leaving food out in the open and store it in airtight containers

• Vacuum at least once a week to remove food particles

• Ventilate crawl spaces to prevent moisture buildup

This story was originally published May 18, 2023 at 7:00 AM.