- Author: Teresa Lavell
Have you seen this little critter? Odds are pretty good that if you haven't yet then you might see it soon. It was first found in California in 2004 in Marin. It has been making its way through the greater Bay Area ever since. I noticed them for the first time last summer. They would scurry around as I was working in the garden and once or twice I found one in the house. I would do periodic checks online but never found any answers. This year after seeing them outside I consulted with the experts! Andrew Sutherland, IPM Advisor for the UC Cooperative Extension, was able to clue me in. Here is his response:
"This species has been increasingly submitted for ID in North Bay counties. Also, it was reported in Berkeley and other East Bay locales last year. Basically, it is an outdoor species with a penchant for coming inside during drought, flooding, or to overwinter. It should be treated as a nuisance 'invader from outdoors' species, similar to Oriental cockroaches (but much smaller and cuter):
- prevent invasions by properly sealing cracks and crevices, providing fine mesh screens for open windows, and installing door sweeps (this exclusion process is a bit difficult to accomplish due to the tiny size of this roach, but it should be the goal)
- eliminate suitable habitat near structures by reducing moisture, maintaining structural perimeters (one meter from foundation) free of dense plantings and mulches, and by reducing sources of decomposing organic matter such as woodpiles and compost heaps (especially in close proximity to doors and windows)
This species does not seem to be attracted to human foods and leavings, so baits developed for other species (German roaches) may not be effective. Pesticides with physical (desiccation) modes of action, such as D.E. and silica gel, will surely have some value in an IPM program, but exclusion and habitat modification should be the main thrusts...
There is currently very little info on this roach. CDFA published a New Species Alert of sorts a few years ago when it was first encountered. You can probably find that online (search CDFA and Phyllodromica trivittata)."
Leave it to an entomologist to say one cockroach is cuter than another! However you describe it, this Mediterranean native will probably get very well established in our local climate. Let's hope it is as cute in its behavior as some think it is in appearance!
Any ideas on how to get rid of them?
Thanks
I am trying to seal up the house to keep them out. If that doesn't work I'll try putting down a perimeter of insecticide or orange oil or something.
I thought they were the nymphs of a newly-introduced roach species, but now understand they don't get larger. I did see one inside when vacuuming a baseboard near a damp corner of the crawlspace. I saw three yesterday when I watered a new plant on the patio. I believe they live in damp areas, like the crawl space, or under bricks and rocks in areas that get water.
The three-lined cockroach is well established in California, especially in the Bay Area and along the central and northern coasts. It has been present in Sonoma County for almost 10 years. We have observed the species as far north as Mendocino County and as far east as Placer County. You're welcome to call the Sonoma County Ag Dept, but the observation will not be news to them. Here's a 2022 blog article my team published that provides some ecological information: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=53670