Sixteen of the 240 (6.6%) control bed bugs were dead at 24 h after treatment (the time of evaluation for all bugs); therefore, for percent control calculations, our results were adjusted using the Abbott correction [
22]. Temprid
®, Transport
®, Invader
®, Cimexa
®, and BBT-2000
® were the only products which showed any substantial (> 40%) bed bug control upon exposure to pre-treated substrates after the six-month waiting period, although results with the resistant bed bug strain were much reduced (see Section below) (
Figure 3 and
Figure 4). Alpine dust
® killed 27% of bed bugs or less, depending on strain and substrate (
Figure 3 and
Figure 4). EcoRaider
® and Mother Earth D
® showed only 11% control or less. Cimi-Shield Protect
® showed no activity whatsoever against bed bugs in this study. It should be noted that diatomaceous earth products (such as Alpine dust
® and Mother Earth D
®) may take several days to produce bed bug mortality [
23].
Further analysis indicated a three-way interaction between treatment, substrate, and bed bug strain (Numerator DF 9; Denominator DF 80; F = 4.90;
p < 0.0001). In that analysis, only Transport
®, Temprid
®, Invader
®, Cimexa
®, BBT-2000
® and Alpine dust
® were significantly different from the water control (
Table 2). Some possible reasons why the other three products showed no difference from water controls could be bed bug deaths in those reps due to handling (all 2400 bed bugs were individually picked up with forceps and placed in petri dishes) or possibly not enough time allowed after exposure for death to occur. However, handling deaths theoretically would be the same for insects used in controls and treatments, and there were 48 h between the time of initial exposure and evaluation.
3.2. Resistant Strain
None of the products tested demonstrated >50% efficacy against the resistant strain of bed bugs. This is not surprising in light of recent studies demonstrating that insecticide resistance is increasing in field populations of bed bugs, even to the successful dual action products, such as Temprid
® and Transport
® [
24,
25,
26]. However, Cimexa
® killed approximately half of resistant bugs on the upholstery fabric, while Temprid
® killed 32% on ceramic tiles (
Figure 4). As for why Cimexa
® (100% amorphous silica gel) seemed ineffective on the tiles, perhaps the powder did not stick to the slick tile surface. Silica gel particles are so lightweight they often suspend in the air following application [
26]. Interestingly, the natural product, BBT-2000
®, composed primarily of cedar and soybean oil, killed 43% of resistant bed bugs on pre-treated tiles, a better result than either Temprid
® or Transport
®. In a previous study, this same product, formerly labeled as Swepe Tite Bed Bug Treatment
®, produced 70% control of bed bugs when exposed to ceramic tiles which had been treated 24 h earlier [
27], thus, there is some evidence that these natural oily products can have a residual effect.
Figure 4.
Efficacy of selected insecticides against a resistant bed bug strain, all reps combined.
Figure 4.
Efficacy of selected insecticides against a resistant bed bug strain, all reps combined.
In their defense, some natural or green products do not claim to kill bed bugs months after treatment. In fact, many of them simply claim to “kill bed bugs on contact.” In this study, we did not test at shorter time intervals to determine the residual life of these products. However, some products do indeed claim a residual effect. Cimexa
® claims that the product lasts up to 10 years if undisturbed, which implies that it would still have activity against insect pests for that time period, and recent field tests with the product have shown great promise [
26]. EcoRaider
® claims to provide “long-lasting” protection but does not define how long that is. The BBT-2000
® label says, “repeat every 1–2 weeks for prevention,” which implies a residual effect for that time period. Mother Earth D
® (diatomaceous earth) says on its labeling, “provides long-lasting control of insect pests.” On a website, Cimi-Shield Protect
® specifically claims to “prevent bed bug infestations for a full year.” This particular claim seems in stark contrast to the data presented here.
There are places and times where natural or green insecticides are warranted for bed bug control, such as in sensitive accounts like classrooms, day care centers, nursing homes, certain areas of hospitals, and the like. However, pest management professionals and homeowners alike should realize that no one product is a magic bullet and an integrated approach to bed bug management is always best.