Abstract
Ultraviolet light traps are commonly used to manage house flies in indoor situations. Many indoor traps are longer than their 46-cm fluorescent tubes and have glue boards to capture attracted flies. Smaller traps have been sold to use in homes and small rooms, but few if any trap evaluations can be found in the literature. One trap, the DynaTrap Flylight DT-3009 (DTFL) has become quite common and a performance evaluation between it and an open-front commercial trap seemed warranted. Evaluations were conducted at the USDA-ARS-CMAVE laboratory in Gainesville, FL. The DTFL and the Gardner GT-200 open-front trap were evaluated individually and then in pairs. Traps were placed approximately 90 cm above the floor at the edge of a 2.4- × 0.76-m wide counter. Traps tested individually were centered on the long axis of the counter. For paired tests, traps were placed approximately 2.1 m apart. Fifty mixed-sex, 3- to 5-d-old house or stable flies were released and counts of captured flies were made after 1, 4, and 24 h. In individual tests, the DTFL and the GT-200 captured 38 and 76% of the house flies, respectively, and 3 and 18% of the stable flies, respectively, after 4 h. At 4 h in paired tests, the DTFL and the GT-200 captured 3 and 66% of the house flies, respectively, and 2 and 16% of the stable flies, respectively. Depending on the intended use, either trap was considered efficacious in capturing house flies when used alone. Differences in trap performance are discussed.
Keywords: ultraviolet light, glue board, plug in trap, Gardner GT-200 trap
Traps with ultraviolet (UV) light as an attractant have been commonly used for capturing indoor and outdoor populations of house flies, Musca domestica L., as well as other filth flies (Lillie and Goddard, 1987; Miller et al., 1993a, b). These traps are usually constructed with a housing that partially encases the fluorescent tubes that produce light in the range of 310–370 nm (Thimijan and Pickens 1973). Many trap models for use in commercial establishments, e.g., stores and restaurants, have one or two 45-cm fluorescent tubes oriented horizontally for best results (Pickens and Thimijan 1986). Models for use in larger spaces, e.g., outdoors, have longer tubes (Hogsette 2019).
Small indoor traps have been commercially available for home use, but lights in many early models were not bright enough to compete well with room lighting or light from nearby windows (Hogsette, unpublished data). The brightness of the light emanating from a trap is a major aspect of it being efficacious (Pickens and Thimijan 1986). In this study, we evaluated a small model trap with a 9-W fluorescent tube that does not appear to shine directly at the viewer. This trap was evaluated alone and in paired comparisons with a representative commercially available open front trap. Although house flies were the main target for this trap, stable flies were added to the evaluations.
Materials and Methods
Study Site and Flies
All evaluations were conducted at the USDA–ARS Center for Medical, Agricultural, and Veterinary Entomology (CMAVE), Gainesville, FL, in a 3.3- × 6.0- × 2.4-m high windowless room with temperature maintained at 23°C. Ceiling-mounted fluorescent lights (16 tubes) constantly illuminated (Hogsette 2008) provided 30-ft candles as required by OSHA (2016). House flies and stable flies (50 of either species per replication, mixed sex, 3–5 d old) from CMAVE colonies (Hogsette 1992) were used for evaluations but fly species were always tested separately. Flies were immobilized with CO2, counted into a release cup, and then allowed to recover for at least 30 min prior to the beginning of a test.
Traps
The DynaTrap Flylight indoor trap, Model DT3009 (DTFL), 6.4 and 8.9 cm wide at the base and light cover, respectively, × 24.1 cm high × 4.5 cm deep at the base (Dynamic Solutions Worldwide, LLC, Milwaukee, WI) with an AtraktoGlo 9-W UV tube, and replaceable StickyTech glue boards (12.7 × 6.4 cm; Fig. 1) was used in this study. This trap was evaluated alone and in combination (tandem) with the Gardner GT-200 trap (48 long × 25 high × 15 cm deep, Gardner, Horicon, WI). The GT-200 was selected for this comparison because it is typical of open-front type UV light traps used in commercial food handling venues for fly management. The GT-200 has two horizontally mounted 20-W UV tubes protected by a metal grid composed of 2.5- × 5.0-cm long rectangular openings (Fig. 2). The trap requires two glue boards, one of which fits vertically behind the tubes (36.8 × 19.7 cm high) and another which is placed horizontally beneath the tubes (38.1 × 8.3 cm wide). Fluorescent tubes in both traps were illuminated for 200 h prior to use to allow phosphors in the tubes to stabilize (Hogsette 2019). Both traps operate on household current.
Fig. 1.
The DynaTrap Flylight DT-3009 showing the front, side, and fluorescent tube. Trap is plugged into an extension cord and placed near a vertically oriented wooden panel to simulate placement near a wall.
Fig. 2.
The Gardner GT-200 showing two 20-W fluorescent tubes and housing with protective metal grid.
Trap Placement
Traps were placed approximately 90 cm above the floor at the edge of a 2.4- × 0.76-m wide counter along the long axis of the study room. This height was based on previous research showing that UV light traps captured the most flies when placed within 1 m of the floor (J.A.H., unpublished data). When tested individually, traps were centered on the long axis of the counter. When tested in pairs, traps were approximately 2.1 m apart at opposite ends of the counter. Traps always faced into the room and trap pairs were parallel to each other. Although the DTFL is designed to be plugged into an electrical wall outlet, for testing purposes, it was plugged into an extension cord so it could be placed at the edge of the counter like the GT-200. To be sure that this freestanding placement did not adversely affect DTFL efficacy, additional tests with the trap at the edge of the counter were conducted with a vertically oriented plywood panel (48 × 41 cm high) placed 10 cm behind the trap to simulate a wall.
Evaluations
To begin a test, single traps or trap-pairs (DTFL and Gardner GT-200) were placed as described above with their tubes illuminated and 50 flies were released into the test room. Numbers of flies captured on each glue board were recorded at 1, 4, and 24 h post-release. Flies on both GT-200 glue boards were added together for a total count. After the 24-h count, live flies remaining in the room were killed in preparation for the next test. Single traps were tested over 6 dates (n = 6); for paired tests, traps were rotated to opposite positions after every test (n = 6 rotations) for a total of 3 complete rotations. After each test, traps were provided with new glue boards.
Statistics
Data from flies captured on traps were analyzed with GLM and means separated with the Ryan–Einot–Gabriel–Welsh multiple range test (SAS Institute, 2014). Unless otherwise indicated, when significance is mentioned in the text, it refers to the P = 0.05 level used for the means separation test. Mean numbers of flies captured were normalized by calculating flies captured per cm2 for each trap.
Results
At 24 h in the single evaluation tests, the DTFL captured about 83 and 33% of the released house flies and stable flies, respectively, compared with 100 and 56%, respectively, captured by the GT-200 (Table 1). The GT-200 captured nearly 50% of the house flies in the first hour compared with 6.0 and 3.6% for the DTFL, with and without the board, respectively. The percent capture for the DTFL increased by the 4-h time interval but was still 50% lower than that of the GT-200 (Table 1). Mean and percent stable fly captures for both traps were much lower than those recorded for house flies and neither trap captured more than 56% of the stable flies after the 24-h exposure period (Table 1). Because mean numbers of house flies captured did not change significantly (t = 0.00, P = 0.9967) when the plywood panel was placed behind the DTFL, subsequent use of the panel was discontinued.
Table 1.
Mean ± SE (cumulative % numbers) and number/cm2 of house flies and stable flies trapped by the DynaTrap Flylight DT-3009 and the Gardner GT-200 individually in a windowless room
| Trap | Fly species | Hours after release | ||
|---|---|---|---|---|
| 1 | 4 | 24 | ||
| DynaTrap Flylight (alone) | HF | 3.0 ± 0.8b (6.0%) 0.037/cm2 | 18.8 ± 2.1b (37.6%) 0.231/cm2 | 41.5 ± 0.9b (83.0%) 0.511/cm2 |
| DynaTrap Flylight (board) | HF | 1.8 ± 0.8b (3.6%) 0.022/cm2 | 18.5 ± 5.8b (37.0%) 0.228/cm2 | 43.0 ± 3.6b (86.0%) 0.529/cm2 |
| Gardner GT-200 (alone) | HF | 24.3 ± 4.7a (48.6%) 0.023/cm2 | 38.2 ± 4.9a (76.4%) 0.037/cm2 | 50.0 ± 0.8a (100.0%) 0.048/cm2 |
| DynaTrap Flylight (alone) | SF | 0.7 ± 0.4a (1.4%) 0.009/cm2 | 1.5 ± 0.4b (3.0%) 0.019/cm2 | 16.3 ± 2.2b (32.6%) 0.201/cm2 |
| DynaTrap Flylight (board) | SF | 1.8 ± 1.2a (3.6%) 0.022/cm2 | 3.8 ± 1.9ab (7.6%) 0.047/cm2 | 14.3 ± 2.6b (28.6%) 0.176/cm2 |
| Gardner GT-200 (alone) | SF | 3.2 ± 1.2a (6.4%) 0.003/cm2 | 9.2 ± 2.7a (18.4%) 0.009/cm2 | 28.2 ± 2.4a (56.4%) 0.027/cm2 |
Traps were placed on a countertop 90 cm from floor. Flies per replication = 50 (n = 6).
Means within fly species in columns followed by the same letters are not significantly different (P = 0.05; Ryan–Einot–Gabriel–Welsh multiple range test [SAS Institute 2014]).
DynaTrap Flylight (board)—to allow light from the trap to reflect from a surface behind the trap, much as it would if the trap had been plugged into an electrical wall outlet, a 48- × 41-cm high plywood panel was placed 10 cm behind trap.
HF = house fly; SF = stable fly.
DynaTrap Flylight glue board area: 12.7 × 6.4 cm = 81.3 cm2; Gardner GT-200 vertical glue board area: 36.8 × 19.7 cm high = 725.0 cm2; horizontal glue board area: 38.1 × 8.3 cm wide = 314.5 cm2; ∑ glue board area = 1039.5 cm2. Flies/cm2 = mean fly number/total glue board area per trap.
Individually the GT-200 greatly outperformed the DTFL at every time interval catching significantly more flies of both species (Table 1). However, when values for mean numbers of flies captured were normalized into flies per unit area, the DTFL performed the same as or better than the GT-200 after the 1-h interval (Table 1). At the 4-h interval, the DTFL would have captured ca. 6 and 2 × more house flies and stable flies, respectively, as the GT-200 if the glue boards on both traps were of equal area (Table 1).
In paired tests, the GT-200 greatly outcompeted the DTFL (Table 2). The cumulative house fly and stable fly percent catch values for the GT-200 trap were similar to those shown in Table 1 when the traps were tested individually. Corresponding percent catch values for the DTFL were relatively flat over time and never exceeded 3.6 and 9.4% for house flies and stable flies, respectively. Per unit area, the GT-200 greatly outperformed the DTFL for capturing house flies at all time intervals, but values were quite similar for stable flies captured by both traps (Table 2).
Table 2.
Mean ± SE (cumulative % numbers) and number/cm2 of house flies and stable flies trapped by the DynaTrap Flylight DT-3009 and the Gardner GT-200 in paired comparisons, by fly species, in a windowless room
| Trap | Flyspecies | Hours after release | ||
|---|---|---|---|---|
| 1 | 4 | 24 | ||
| DynaTrap Flylight (tandem) | HF | 1.0 ± 0.3b (2.0%) 0.012/cm2 | 1.7 ± 0.9b (3.4%) 0.021/cm2 | 1.8 ± 0.5b (3.6%) 0.022/cm2 |
| Gardner GT-200 (tandem) | HF | 20.3 ± 2.8a (40.6%) 0.020/cm2 | 33.2 ± 4.1a (66.4%) 0.032/cm2 | 46.5 ± 1.3a (93.0%) 0.045/cm2 |
| DynaTrap Flylight (tandem) | SF | 0.7 ± 0.4b (1.4%) 0.009/cm2 | 1.0 ± 0.5b (2.0%) 0.012/cm2 | 4.7 ± 1.3b (9.4%) 0.058/cm2 |
| Gardner GT-200 (tandem) | SF | 2.3 ± 0.5a (4.6%) 0.002/cm2 | 8.2 ± 2.4a (16.4%) 0.008/cm2 | 27.5 ± 2.6a (55.0%) 0.027/cm2 |
Traps were placed on a countertop 90 cm from floor. Flies per replicate = 50, n = 6.
Means within fly species in columns followed by the same letters are not significantly different (P = 0.05; Ryan–Einot–Gabriel–Welsh multiple range test [SAS Institute 2014]).
HF = house fly; SF = stable fly.
DynaTrap Flylight glue board area: 12.7 × 6.4 cm = 81.3 cm2; Gardner GT-200 vertical glue board area: 36.8 × 19.7 cm high = 725.0 cm2; horizontal glue board area: 38.1 × 8.3 cm wide = 314.5 cm2; ∑ glue board area = 1039.5 cm2. Flies/cm2 = mean fly number/total glue board area per trap.
Discussion
Single DTFL units placed 90 cm above floor surface effectively collected house flies indoors. As expected, these units did not perform as well against stable flies, and only reduced indoor stable fly populations by 30% (Table 1). The fly density used for these tests was much higher than expected indoors, except at animal facilities; indoor UV light traps are used mainly for indoor house fly control (Lillie and Goddard, 1987; Miller et al., 1993a, b). However, other muscoid flies, especially calliphorids and occasionally stable flies, can be captured if exposed to these traps (J.A.H., unpublished data).
It was not surprising that the Gardner GT-200 captured significantly more flies at every time interval when in competition with DTFL (Table 2). A major factor, as determined by Pickens and Thimijan (1986), is the brightness of the GT-200, which has two 20-W tubes compared with the single 9-W tube in the DTFL.
Pickens and Thimijan (1986) also determined that horizontal orientation of the tubes produces the best fly catch. The UV tube in the DTFL is oriented vertically. However, the glue board is placed in front of the tube and prevents it from being visible through the front of the trap housing (Fig. 1). The ability of this trap to capture up to 83% of the released flies in 24 h appears to question the importance of trap brightness (Pickens and Thimijan 1986). When the DTFL is operated in a room with overhead lights turned on, it is difficult to tell that the trap is illuminated. Brightness inside of the housing has been maximized by folding the tube into a tight “U” shape, essentially placing two 9-W tubes side by side. This doubles the brightness inside of the housing, but this light is directed out the top, sides, and back of the trap.
The GT-200 glue boards have 12.8 times the area of the DTFL glue board. As shown by the data, this did not reduce the efficacy of the DTFL. However, in situations where fly density is high, glue board replacement intervals will be shorter as the glue boards will fill up faster with trapped flies.
In conclusion, the DTFL performed much better than expected for a small trap. The relatively dark front of the housing did not adversely affect the trap’s propensity to attract and capture flies as would be expected with a closed front trap (Hogsette 2008). On an individual basis it compared well the GT-200, although the GT-200 captured flies at a faster rate. Capture rate of the DTFL was low during the first hour of exposure but increased 6 × by the 4-hr exposure period. Because the DTFL does not need a wall directly behind it to effectively attract and capture house flies and stable flies, plugging it into an extension cord greatly increases its portability and versatility. More research is needed to validate the DTFL design, especially if a larger model of the trap was developed.
Acknowledgments
We thank Heather Furlong for her assistance with this project. The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, nor the U. S. Government. Both authors are employees of the U.S. Government. This work was prepared as part of their official duties. Title 17, U.S.C., §105 provides that copyright protection under this title is not available for any work of the U.S. Government. Title 17, U.S.C., §101 defines a U.S. Government work as a work prepared by a military Service member or employee of the U.S. Government as part of that person’s official duties.
Contribution of Authors
J.A.H. carried out the laboratory work. J.E.C. conceived, designed, and coordinated the study. All authors gave approval for publication and agree to be accountable for the content.
Competing Interests
The authors declare no competing interests.
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