Getting to know the Turkestan cockroach

Cockroaches have historically been a top pest and reliable source of business for PMPs.  Indeed, from day one most new technicians are taught to recognize the four most commonly encountered species:

• the German cockroach--one of our smaller cockroaches, bane of restaurants and homes
• the American cockroach (a fast and intimidating insect that looks twice as big as it really is when running across a floor or flying)
• the black, rather nasty Oriental cockroach--pest of sewers and the grounds around buildings
• the smoky brown cockroach, an outdoor cockroach unafraid to venture into homes. 

Other common species, depending on your part of the country, include the Australian, brown, brown-banded, Asian and field cockroaches.

Figure 1. The adult female S. lateralis (A) and adult female Oriental
cockroach (B) are similar in size and color. Arrow points
to the distinguishing light marking on the forewing margin
of the Turkestan cockroach. Photo modified from Kim and
Rust (2013).

In many parts of the country pest management professionals need to add the invasive Turkestan cockroach (Shelfordella lateralis Walker) to their watch list. This Asian invader is quickly making a name for itself and moving through Texas and other states.

Because the Turkestan cockroach looks similar to other species, you may already have seen it and not realized it was something new. Female Turkestans look like Oriental cockroaches. Male Turkestans look like small American cockroaches or perhaps an innocuous field roach.

Spread

The Turkestan cockroach has becoming a significant new pest since it was first reported in Shelford, California in 1978 and El Paso, Texas in 1979.  It has since spread through Arizona and New Mexico, across Texas and even to Georgia.  This week I got my first north Texas specimen, and tentatively identified an emailed photo from Tennessee as a Turkestan cockroach.

Figure 2. To my knowledge, this is the first Turkestan cockroach
recorded from north Texas. Collected from a hotel in Frisco,
TX (VII-29-2019). Note the pale, almost transparent border
at the margin of the forewing, and the size (28 mm/one inch),
which is smaller than a typical American cockroach. Photo
M. Merchant.

If you think this pest won't reach your area soon, think again. Internet commerce is also at work. Turkestan cockroaches are commonly sold online where they are well known in the pet trade as "red runners." They provide food for reptile, amphibian and small mammals. Pet owners like the fact that Turkestan cockroaches breed quickly, do well in captivity and don't climb glass (so are easy to keep in aquaria).

My first North Texas specimen of a Turkestan cockroach came this week courtesy of Emory Matts, with Rentokil Steritech.  Guests at a local hotel recently started complaining of roaches on several floors. Whether this was an invasion from outdoors (males can fly and are attracted to lights at night), or represented an indoor infestation could not be determined.  Though it's often referred to as an "outdoor" insect, the Turkestan is capable of establishing itself indoors, similar to Oriental and American cockroaches.

Competition

Figure 3. Turkestan (A) and Oriental cockroach nymphs.
Notice the reddish-brown thorax and dark abdomen of
the Turkestan nymph compared to the uniform brown color
of the Oriental. Photo from Kim and Rust (2013).

According to Kim and Rust (2013), the Turkestan is replacing the Oriental cockroach throughout much of the Southwest as the most important cockroach pest around the outsides of structures.  Common breeding sites are similar to those of Oriental cockroaches, including water meter and irrigation boxes, electrical boxes, hollow block walls, cracks and crevices in concrete, compost piles and potted plants.  However, it appears that in the warm climates of the Southwest, Turkestan cockroaches rush through their 5 nymph stages faster than the Oriental with its 7-10 nymph stages.  A female Turkestan cockroach will produce about 25 oothecae (egg cases) in her lifetime compared to 5-10 oothecae for an Oriental cockroach.  The numbers tell the story as to why Turkestan cockroaches are taking over.

Distinguishing Turkestan cockroaches

The immature Turkestan roach resembles both Oriental and American nymphs in general appearance (Fig. 3).  The Oriental cockroach, however, is uniformly dark-brown and the American cockroach is uniformly reddish brown.  The Turkestan, in contrast, is reddish-brown on the head and  thorax (pro- and meso-thorax) and dark-brown only on the rear of the body.

Figure 4. American (top) and Australian cockroaches. 
Note the bold markings on pronotum and the
forewings of the Australian cockroach, in contrast
with the American, which lacks forewing markings.
Photos, M. Merchant.

Besides size (the male Turkestan cockroach is smaller), American and Australian cockroaches can be distinguished by both the wing borders and markings on the prothorax (shield behind the head)(Fig. 4).  Forewing margins of the Turkestan cockroach are pale and almost transparent compared to the uniform-colored wings of the American, and the bold yellow margins of the Australian. Click here for another image of male and female Turkestans.

Control

Research on control methods for the Turkestan cockroach is still limited; however control methods should be similar as for the Oriental cockroach. Granular cockroach baits can be effective; however, Kim and Rust suggest that higher reproductive and growth rates for the Turkestan cockroach could mean that technicians should need more bait when treating.  Special attention should be paid to pest proofing doors and other building entry points to keep cockroaches outdoors where they pose the least trouble.

Reference:

Kim, T. and M. Rust. 2013. Life history and biology of the invasive Turkestan cockroach (Dictyoptera: Blattidae). J. Econ. Entomol. 106(6): 2428-2432.