Turkestan Cockroaches: The Roach Taking Over Southern California Yards

It usually starts at the porch light. On a warm Southern California evening, a slender, reddish-tan insect about an inch long comes gliding in and lands near the door, and your first thought is that a small cockroach just flew at you. Or it starts when you lift the lid on your water-meter box and a cluster of dark, fast-moving roaches scatters into the soil. Both are the same insect: the Turkestan cockroach, an invasive species most homeowners have never heard of but are increasingly seeing. Over the past two decades it has quietly spread across the region and is now steadily replacing the Oriental cockroach as the most common roach living in Southern California yards.

The Turkestan cockroach is native to a band of the world stretching from North Africa through the Middle East and into Central Asia — the historical region of Turkestan, which gives the insect its name. It was first detected in the United States in 1978 at the Sharpe Army Depot in Lathrop, California, and entomologists believe it arrived on military equipment shipped back from Central Asia. For a couple of decades it stayed a curiosity. Then it started moving.

By around 2001 it was confirmed as an established, breeding population in Los Angeles County, and in the years since it has spread throughout the South Bay, the greater LA area, and much of the Southwest. Today, across large parts of Southern California, it has overtaken the Oriental cockroach as the roach you are most likely to find living outdoors around a home. If you have noticed more roaches in your yard, your water-meter box, or flying at your lights in recent years, this is very likely the species behind it.

The reason so few homeowners know the Turkestan cockroach by name is that it is almost always mistaken for something else. And here is the part that makes identification genuinely confusing: the males and females look so different from each other that they are commonly mistaken for two entirely different species.

The females are dark and stout and get called Oriental cockroaches. The males are slender and tan and can fly, so they get called American cockroaches. Two very different-looking insects, one species — and neither of the roaches people think they are seeing.

A female Turkestan cockroach is about an inch long, broad-bodied, and dark brown to almost black — which is exactly why she gets confused with the Oriental cockroach, another dark, ground-dwelling roach common in the same damp outdoor spots. The giveaway is the coloring around the edges. A female Turkestan has distinct cream or pale-yellow markings along the sides of the shield behind her head (the pronotum) and along the margins of her short wing pads. The Oriental cockroach, by contrast, is a uniform glossy black or very dark brown with no pale markings, and has a noticeably broader, wider body. If you are looking at a dark roach with cream trim, it is a Turkestan.

A male Turkestan cockroach looks nothing like the female. He is slender, reddish-tan to light brown, with long, pale yellowish wings edged in cream that extend the length of his body — and, unlike the female, he can fly. Because he is winged and reddish, he gets mistaken for the American cockroach, the large roach many people picture when they think "big flying roach." The difference is size. A male Turkestan is only about three-quarters of an inch to an inch long; an American cockroach is a full 1½ to 2 inches, distinctly reddish-brown, with a pale yellow figure-eight pattern behind the head. If a roach flew to your light and it is under an inch long, it is almost certainly a male Turkestan, not an American.

When two similar species compete for the same outdoor niche, small biological advantages decide the outcome — and the Turkestan cockroach has several over the Oriental cockroach it is displacing.

Here is the most important thing to understand about this roach: it is a peridomestic pest, meaning it lives and breeds outdoors, around the structure — not inside it. Unlike German cockroaches, which set up permanent breeding populations in kitchens and bathrooms, Turkestan cockroaches do not establish indoors and cannot sustain a population inside a typical home. When they show up inside, it is almost always an individual that wandered or flew in, usually looking for water, and it typically does not last long indoors.

That said, "they wander in" still means you keep finding them. The common ways they get inside:

Because Turkestan cockroaches live outside, the most effective thing you can do is make the outside of your home less livable for them and seal the routes they use to get in. This is where homeowners have real leverage.

One or two roaches a season, handled by tightening up door sweeps and reducing moisture, is something most homeowners can stay on top of themselves. It is worth calling a professional when you are seeing them repeatedly — multiple sightings a week, roaches turning up indoors again and again, clusters in the water-meter box or along the foundation, or a steady stream of males at the lights all summer. That pattern means there is an established outdoor population producing them faster than exclusion alone will fix.

Because the roaches live outside in harborage you cannot easily reach, the treatment is fundamentally an exterior job — which is also why indoor sprays and foggers do so little for this pest. Here is how we approach it: