The Asian cockroach, Blattella asahinai, is an exotic invasive species first detected in Florida in 1986. This insect now occurs everywhere in Florida and has become established throughout the Southeastern U.S. Large populations of Asian cockroach build up outdoors and subsequently infest homes, making the Asian cockroach a household pest. Large populations in rural areas can also occur in agricultural fields.
Asian cockroaches observed in and near lettuce fields of the Everglades Agricultural Area of Florida have become an increasing concern for local lettuce producers. Although Asian cockroaches do not feed on lettuce, their presence cannot be tolerated because the presence of insect injury or of insects, dead or alive, can throw lettuce heads out of grade or even lead to rejection of shipments. In addition, cockroaches can be a potential food safety issue because they may come in contact with contaminated habitats before moving into lettuce fields.
Asian cockroach management consists of preventive insecticide applications in lettuce fields with as many as five applications per crop cycle. It also consists of frequent insecticide applications on field surroundings, irrigation equipment, packing equipment and supplies, and portable toilets for farm employees. This management approach is generally preventive and indiscriminate as lettuce harvest approaches. It is expensive, increases potential non-target impacts, and increases the risk of insecticide resistance. Thus, Asian cockroach management is not sustainable.
Trap-assisted scouting, in and around lettuce fields, will answer the need for a refined, more sustainable, management strategy because scouting relying on traps would be consistent regardless of personnel. In addition, trap-assisted scouting would provide continuous sampling of Asian cockroach populations in a specific area, which would be expected to more accurately estimate cockroach populations.
Mexican rice borer pheromone traps can reflect changes in Asian cockroach population dynamics and could be used to monitor Asian cockroach populations. Asian cockroaches live in leaf litter and are attracted to landscaping mulches. Red rubber mulch is attractive to nymph and adult cockroaches. This observation suggests that pan traps with a layer of mulch may be used to monitor Asian cockroach populations.
The proposed on-farm research project will have two objectives:
- Compare the performance of traps for sampling Asian cockroaches to select traps that could be used in a trap-assisted scouting program.
- Deploy best performing traps in lettuce fields and adjacent areas to determine the benefits of a trap-assisted scouting program for Asian cockroaches.
Consistent with the project proposal, two experiments compared six trap treatments on a commercial lettuce farm during the spring (4/19/18-5/10/18) and fall (10/19/18-11/15/18). The trap treatments included green/yellow/white Universal Moth bucket traps placed 0.5 foot above the soil surface with a Mexican rice borer pheromone lure and an insecticidal strip, or with an insecticidal strip only, or without pheromone lure or insecticidal strip. The other three trap treatments included baking aluminum foil pans placed on the soil surface with a 1-inch layer of red rubber mulch, or with a one-inch layer of sugarcane bagasse, or empty.
Each trap treatment was deployed in eight commercial lettuce fields and two farm shop areas. In each field, the six traps were placed in a random order along a longitudinal transect, at an intertrap distance of 100 feet. In each farm shop area, the six traps were placed at a random location, at an intertrap distance > 5 feet. Thus, the experiments followed randomized complete block designs with 10 blocks (1 replicate/block). Traps were checked for Asian cockroaches once a week.
Because Asian cockroach trap captures were low in bucket and pan traps, an additional field experiment was conducted during the winter (2/22/19-2/25/19). This experiment was conducted to determine the feasibility of using Lo-Line cardboard sticky traps developed for indoor cockroach management. Lo-Line traps with a beer plus bread bait, with InVite roach bait, or without additional bait were deployed in eight fields and two shop areas consistent with the previous experiments (10 blocks and 1 replicate/block). The traps were checked once for Asian cockroaches.
In the first field experiment, only two Asian cockroach adults were captured in the 60 traps over 21 days. These adults were in bucket traps with an insecticidal strip only.
In the second experiment, 43 Asian cockroaches (83.7% adults) were captured in the 60 traps over 27 days. The number of cockroaches was significantly (P < 0.001) greater in bucket traps with a Mexican rice borer pheromone lure and an insecticidal strip (0.55 cockroach/trap/week) than in any other trap. These observations showed that cockroaches, adults and nymphs, were present in all areas of the fields and of the farm shop during the lettuce production season, regardless of insecticide treatments. However, the number of cockroaches in traps was low relative to cockroach activity observed while checking the traps. In addition, for the six pan traps in the farm shop areas, checking for cockroaches under the pans revealed the presence of 0.625 cockroaches/trap/week (73.3% adults). These observations under the traps show that Asian cockroaches find shelter in cryptic locations in areas of the farm near lettuce packing and storage activities.
In the third experiment, Lo-Line traps maintained their integrity outdoor under dry weather conditions. However, only one cockroach was captured in a trap with InVite roach bait. These observations suggest that Lo-line traps could be used for Asian cockroach monitoring on lettuce farms although adverse weather conditions might have negative impacts on the traps.
Educational & Outreach Activities
Farm consultations occurred during trap set up and sampling. Topics included biology of Asian cockroaches, available management tactics, purpose of the SSARE OFRG project, and observations associated with the SSARE OFRG project.
There were two presentations at meetings of the Florida Lettuce Advisory Committee held at the UF/IFAS Everglades Research and Education Center in Belle Glade, FL. Presentations were entitled “Mitigation of insects as foreign objects in harvested lettuce” on 10/3/18 and “Insect pest management update” on 2/27/19.
Knowledge of insect pest biology
Knowledge of insecticide options
Project outcomes have been limited so far because the traps have not performed as well as expected. However, the project has formally documented the presence of Asian cockroaches in commercial lettuce fields and in farm shop areas, which had not been done before. This aspect of the project has raised awareness of the problem among stakeholders and will assist in providing justification for future work. In addition, the project increased the presence of research/extension personnel on commercial lettuce farms and has increased communication between farmers and research/extension personnel.