Turkestan cockroaches are common at schools throughout California. Adapted to dry climates, they live in the landscape and cracks in the hardscape, coming out at night to forage for food. If buildings are not sealed, cockroaches can get inside classrooms, locker rooms, and food prep or storage areas, leading to pesticide applications indoors and outdoors.
School districts typically respond to outdoor cockroaches with building perimeter pesticide applications. Unfortunately, pest control programs will fail without exclusion measures (e.g., door sweeps and seals). Furthermore, strict regulations for pesticide applications at sensitive sites like schools require posting for pesticide applications; notification of parents, teachers and staff; and pesticide use reports.
Inside buildings, insecticide bait has been the standard management practice for decades for indoor cockroaches like German cockroaches. It is very effective. “Baiting has changed the way we do pest control indoors. There are a lot fewer indoor insecticidal sprays now,” says Area IPM Advisor Andrew Sutherland. When the bait is eaten, the cockroach dies. Dead cockroaches may also be eaten by other cockroaches, poisoning them as well. The insecticide can move through the cockroach population and cause the numbers to fall quickly.
“Why don’t we use baits outdoors?” Sutherland asks. He wants outdoor bait programs to become more common, but many were skeptical that they could work. Baits work best when placed near areas where cockroaches breed and hide. Gel baits lose water very quickly in areas of high temperatures and low relative humidity. Dust and debris coat the surface of the bait and make it less attractive.
Funding from the California Department of Pesticide Regulation and the National Pest Management Association enabled Sutherland to investigate whether baits could be effective outdoors in hot and arid environments. The first step was to conduct lab tests with bait dried as if by environmental conditions found outdoors. The dried-out baits were still attractive to cockroaches and still effective at killing them.
Then, at two schools, baits were tested outside in self-contained tamper-proof bait stations typically used for rodent management. The bait stations were mounted to hardscapes or bolted to the floor near areas with cockroaches. In subsurface utility ports, Sutherland placed polyvinyl chloride (PVC) slip couplings with bait. Sutherland states, “Talking to pest management professionals about applying bait using PVC slip couplings, there was lots of interest for using this method in the field. You can see if the bait is being consumed. It’s not as messy. And you can prep these bait placements before you go out. You can apply bait within the couplings while in the shop, put them in a container, and they’re ready to take into the field and place out.” In this study, old bait was removed and replaced with fresh bait once per month.
“Talking to pest management professionals about applying bait using PVC slip couplings, there was lots of interest for using this method in the field. You can see if the bait is being consumed. It’s not as messy. And you can prep these bait placements before you go out. You can apply bait within the couplings while in the shop, put them in a container, and they’re ready to take into the field and place out.” —Andrew Sutherland
In addition to baiting, both schools invested in door sweeps and hardscape sealants to prevent cockroaches from getting inside. Insecticidal foam targeted the areas where cockroaches breed and hide. Training to use baits was provided to school personnel and pest control technicians.
Monitoring for cockroaches indicated whether management practices were working and also identified hotspots and places where roaches breed and hide so that exclusion efforts could be focused there. Cockroach numbers were measured three ways: overnight glue traps, overnight jar traps, and night surveys. Glue traps were placed near exterior doors to measure the number of cockroaches that could potentially invade the buildings. Jar traps had food inside to attract cockroaches and masking tape on the outside so cockroaches could climb into, but not out of, jars. Night surveys entailed walking the treatment area and counting roaches.
In just one month, numbers of cockroaches crashed. The project was continued for a full year (including winter months, November through March, when it’s too cold and wet for cockroaches to forage for food). Roach numbers stayed low to nonexistent for the full year at both schools. Both school districts have maintained their baiting programs to continue to keep cockroaches out of school buildings.
Sutherland designed an effective cockroach management program that reduces outdoor numbers and prevents cockroaches from entering structures. This program can be used in schools and child care environments without the posting and notification requirements, saving school personnel and pest management professionals time and effort. This demonstration of the efficacy of outdoor baiting for Turkestan cockroaches benefits California, other states, and countries worldwide that may rely on applications of liquid pesticides to manage outdoor pests.