Final report for OS18-113
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.
The use of traps to assist scouting is expected to contribute to 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 for management.
This 2-year project compared different trap types for sampling of Asian cockroaches on a lettuce farm. Lo-Line sticky traps baited with blattellaquinone performed best, and these traps can be used to compare relative levels of cockroach populations among particular locations on a farm. For example, observations suggest that sugarcane fields bordered by weedy habitats are a greater source of Asian cockroaches infesting lettuce than sod fields. Thus, Lo-Line traps baited with blattellaquinone are tools that can be used to refine Asian cockroach management. However, the relationship between visual observations in lettuce fields and trap captures is unknown. In addition, trap capture efficiency might be low, cost might be an issue, and blatellaquinone lures are not available commercially.
The on-farm research project had 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 to detect changes Asian cockroach infestation levels and determine the influence of adjacent areas toward a trap-assisted scouting program.
All experiments were conducted on the same commercial farm in Palm Beach County, Florida.
A first series of experiments focused on comparing the performance of traps for sampling Asian cockroaches to select traps that could be used in a trap-assisted scouting program (objective 1).
Two experiments compared six trap treatments 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 6 inches 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 tied vertically to a piece of rebar, approximately 6 inches above the soil surface. The traps were checked once for Asian cockroaches.
One experiment further studied the performance of six trap treatments for sampling Asian cockroaches during the fall (11/13/19-12/6/19). The traps included green/yellow/white Universal Moth bucket traps with an insecticidal strip, aluminum foil pans with red rubber mulch and an insecticidal strip, and Lo-Line traps. Each of these traps were deployed with and without a rubber septum loaded with 100 µl of blatellaquinone dissolved in hexane at 0.1 µg/µl. Blatellaquinone is the major component of the sex pheromone emitted by German cockroach females and it attracts male Asian cockroaches under field conditions (Matos and Schal. 2015. Environ. Entomol. 44: 1155–1160). Thus, it was hypothesized that the use of blatellaquinone would increase the performance of traps. The number of replications and trap placement was the same as for the first two experiments conducted in 2018. Traps were checked for Asian cockroaches and pheromone lures and Lo-Line traps were replaced once a week.
A final experiment was conducted during the winter (2/10/20-3/9/20) using the best performing traps in lettuce fields to further evaluate blatellaquinone lures, detect population fluctuations, and determine the potential influence of adjacent habitats (objective 2). Fifty Lo-Line cardboard sticky traps were deployed over a 285-acre area containing lettuce fields bordered by sugarcane and weeds (southern and western edges) and sod (northern and eastern edges). Traps were placed along five parallel transects that were 0.5 miles long. For each transect, there were 5 locations 600 feet apart. At each location there was 1 trap with and 1 trap without lure at an intertrap distance of 50 feet. Traps were checked for adult Asian cockroaches and were replaced once a week.
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.
In the fourth experiment, 115 Asian cockroaches (85.2% adults) were captured in the 60 traps over 23 days. Trap captures in the three trap types confirmed results of the first year, with cockroaches present in all areas of the farm. The number of cockroaches was significantly (P < 0.001) greater in the Lo-Line traps with blatellaquinone (1.93 cockroaches/trap/week) than in any other trap (<0.87 cockroach/trap/week). Thus, results of this experiment suggested that sticky traps baited with a sex pheromone component were the most effective traps tested since the initiation of the project.
In the fifth experiment, 577 adult cockroaches total were captured in the 50 traps over 28 days. The addition of blattellaquinone significantly (P = 0.008) increased cockroach captures in Lo-Line traps (3.7 vs. 2.2 cockroaches /trap/week), consistent with the fourth experiment. Trap captures changed (P < 0.001) among the four weeks of the experiment, decreasing from 4.8 cockroaches/trap/week during the first week to 0.9 cockroaches/trap/week during the fourth week. In addition, more cockroaches (P < 0.001) were captured in traps near sugarcane and weedy habitats (5.0 cockroaches/trap/week) than near sod (1.4 cockroaches/trap/week).
This 2-year project compared different trap types for sampling of Asian cockroaches on lettuce farms in Florida. Lo-Line sticky traps baited with blattellaquinone lures performed best, and these traps can be used to determine relative levels of cockroach populations among particular locations on a farm. For example, observations of this project suggest that sugarcane fields bordered by weedy habitats are a greater source of Asian cockroaches infesting lettuce than sod fields. Thus, Lo-Line traps baited with blattellaquinone are tools that can be used to refine Asian cockroach management. However, the relationship between visual observations in lettuce fields and trap captures is unknown. In addition, trap capture efficiency might be low, cost might be an issue, and blatellaquinone lures are not available commercially.
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 three 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, “Insect pest management update” on 2/27/19, and “On-farm insect sampling with traps: Where do we go from here?” on 3/12/20. Meetings of the Florida Lettuce Advisory Committee are held twice a year and involve farmers, crop consultants, extension agents, personnel of the Florida Department of Agriculture and Consumer Services, and researchers of the University of Florida.
A face-to-face meeting was held on 3/12/20 with four lettuce farmers growing >75% of the lettuce in southern Florida. Project results and potential future on-farm research projects were discussed.
The publication of one UF/IFAS extension article and one peer-reviewed research article focusing on Asian cockroaches on lettuce farms in Florida was included in the project proposal. Although famers are concerned about Asian cockroaches and very supportive of research addressing sustainable management, they are extremely concerned about client and public perception of cockroach problems in their crop. Thus, it was decided to avoid the publication of a broadly available extension publication and to focus on face-to-face exchange of information. The data collected during this on-farm project have not been included in a research publication at the time of this report. However, the data combined with data of future work building on this project will ultimately be included in a research publication.
Knowledge of insect pest biology
Knowledge of insecticide options
Knowledge of traps as sampling tools
Project outcomes have been limited because the traps did not perform as well as expected during the first year of the project. However, the project increased researcher and farmer knowledge. The project formally documented the presence of Asian cockroaches in commercial lettuce fields and in farm shop areas, which had not been done before. The project identified areas of the cooperator’s farm at higher risk of cockroach infestations (i.e., areas adjacent to sugarcane and weedy borders). In addition, the project demonstrated that Lo-Line sticky traps baited with blattellaquinone can be used to sample Asian cockroaches in lettuce fields. This change in knowledge is expected to change farmer behavior. Although the widespread adoption of traps as a sampling method to assist scouting is not expected in the near future, farmers have expressed interest in potential use of traps in cases when current sampling and management do not provide satisfactory results. The project also increased the presence of university personnel on commercial lettuce farms and has increased communication between farmers and university personnel. Thus, another outcome is the expected increased collaboration between farmers and university personnel. Collectively, changes in knowledge and expected changes in behavior are expected to better inform insecticidal management, avoiding unnecessary insecticide applications in fields or areas with low Asian cockroach populations.