The Turkestan cockroach, the rusty red and the red runner…Blatta lateralis goes by many names. Introduced to California and Texas in the late 1970s, probably hidden within military equipment brought back from the Middle East, the species is now common throughout urban and suburban landscapes of the American Southwest. Interestingly, this cockroach is readily available for purchase online as a popular live food source among reptile enthusiasts, likely contributing to its widespread distribution. Turkestan roaches are closely related to the more familiar oriental cockroach, Blatta orientalis. Both species live primarily outdoors in urban settings and will often be found inhabiting moist sheltered locations such as irrigation and electrical boxes, concrete cracks and crevices, and hollow block walls. In many cases, foraging cockroaches may enter structures that are not properly sealed, triggering complaints and calls for pest control services. Entomologists and PMPs alike have observed a displacement of oriental cockroaches by Turkestan cockroaches in some areas. This is most likely due to the Turkestan’s rapid development from egg to adult, their ability to produce more eggs than the oriental cockroach and better adaptations for survival in arid climates.
Traditionally, professionals have sought to exclude these invading pests using perimeter protection programs, where liquid formulations insecticides are regularly applied around building exteriors. But what happens if we aren’t allowed to use such products? Do we wave the white flag? Not a chance: we believe there are currently a number of highly effective outdoor cockroach baits on the market that represent important alternatives to perimeter sprays. These should be strongly considered when local regulations prohibit sprays, when insecticide resistance is suspected, or when minimizing exposure risk at sensitive sites or within integrated pest management (IPM) programs.
One major hurdle with perimeter protection programs is that state and federal policies often restrict and heavily regulate professional use of pyrethroids, commonly found in sprays, particularly when applied to impervious surfaces (buildings, concrete and other hardscape elements), due to concerns about surface water contamination. Also, sensitive sites such as schools, child care centers and hospitals provide challenging pest control settings since they may have additional restrictions and require notifications prior to sprays. PMPs working in these environments can reduce time and labor by designing IPM programs that are exempt from these requirements. Finally, repeated and widespread use of pyrethroid insecticides has caused many insects to develop resistance to the active ingredients within these sprays, making long term management more challenging.
Recently, the NPMA sponsored a University of California research team in order to evaluate the efficacy of insecticidal baits as alternatives to liquid sprays for management of Turkestan and oriental cockroaches, focusing on sensitive sites. A series of lab assays were performed at UC Riverside, and field trials were conducted at two public schools that were experiencing Turkestan cockroach infestations, one in northern California (Mendocino county) and one in southern California (Riverside county). The northern California field site had been unsuccessfully battling an extremely large population for several years while primarily using perimeter sprays of pyrethroid insecticides.
If you’ve ever applied gel baits outside during the hot and dry summer months in California (or elsewhere in the American Southwest), you’ve probably noticed how quickly they dry out and become brittle. One of the questions addressed through this study was how effective gel baits are after that ageing process. In a lab setting, five different baits were intentionally dried out and then provided to groups of cockroaches in plastic containers. Exposure to both fresh and dried bait caused widespread mortality, with 70%-100% of cockroaches dead within 14 days. This is where it gets really interesting: in some cases, very little bait was consumed, but mortality was still high. We observed that some of the cockroaches were playing with their food; dragging bait granules or chunks of dried gel around the study arena. This suggests that contact with bait may be enough to kill an individual and that substantial bait consumption is not always necessary.
COMBINATION OF CHEMICAL AND NON-CHEMICAL TACTICS
Considering the large population of Turkestan cockroaches found at the northern site, a robust IPM program needed to be implemented there in order to be successful, combining several chemical and non-chemical tactics. Sweeps were installed on exterior doors to restrict access to classrooms, cafeterias and kitchens. Pipe penetrations, conduit access points, cracks, vents and other structural defects were sealed with appropriate materials. Additionally, trashcans throughout campus were raised on pedestals to eliminate harborage areas under cans.
Next, evaluations of three insecticidal baits (two gels and one granule) were conducted using targeted outdoor applications. Because California’s Healthy Schools Act requires special posting and notification prior to ‘uncontained’ insecticide applications, baits were distributed using two novel self-contained, tamper-proof methods: inside 1″ PVC irrigation slip couplings placed within in-ground boxes (irrigation valve, water meter and sewer cleanout) and within lock-and-key rodent bait stations (Protecta RTU) affixed to concrete surfaces. Initially, the maximum label rate of bait products was applied (3g deposits, 12g per treatment area per month), but rates were reduced (1g deposits, 4g per treatment area per month) as cockroach numbers declined. Old bait deposits were removed and replenished monthly throughout the study according to label guidelines.
What we found was that within a month of this one-year study, populations were significantly reduced at both schools. We observed 80%-90% control of Turkestan cockroaches in areas treated with bait. In areas where no baiting occurred, cockroach populations at the southern site remained high, while populations at the northern site decreased by 50%. We believe that this unexpected decrease seen in the untreated areas of the northern site was due to a large initial population, larger foraging ranges than were previously expected (treatment areas were only separated from one another by about 100 feet) and the consumption of bait-intoxicated cockroaches by their own kind. Such cannibalism was commonly observed in our overnight trapping programs, with trapped cockroaches being dismembered and consumed by their comrades.
Our lab results and field observations suggest that many different professional cockroach baits are attractive to Blatta species, even when the insects have access to alternative food and water sources. Gel bait deposits can effectively kill cockroaches even if they have been dried out for some time. Bait programs give PMPs additional options for cockroach management when perimeter protection programs are restricted, unavailable or ineffective.
ABOUT THE PEST MANAGEMENT FOUNDATION
The Pest Management Foundation is a charitable organization affiliated with the National Pest Management Association but is a separate entity with a unique Board of Trustees focusing on serving the industry by advancing research and education in urban/structural pest management. The Pest Management Foundation is funded entirely through donations from individuals and companies. All donations are tax deductible—both personal and corporate donations are accepted. To learn more about the Pest Management Foundation, visit www.npmafoundation.org.
This work was made possible through collaborations with Dr. Mike Rust, Dr. Siavash Taravati, Dr. Dong-Hwan Choe and Kathleen Campbell. Funding provided by the National Pest Management Association, and many outstanding images provided by Joyce Gross.
Tina Kim, Michael K. Rust; Life History and Biology of the Invasive Turkestan Cockroach (Dictyoptera: Blattidae), Journal of Economic Entomology, Volume 106, Issue 6, 1 December 2013, Pages 2428-2432, https://doi.org/10.1603/EC13052.