Heat Cold Controlled atmospheres

Public Health Significance of Urban Pests 145

4.5.4.4. Steam

Some pest managers have effectively used steam treatments to quickly eliminate live bugs and their eggs from the seams of mattresses and other cloth items. Effective use of this technique requires practice and care. Manufacturer’s instructions about the steam gene- rating devices’ operation, maintenance and safety precautions must be followed carefully. To be effective, the steam emission tip must be about 2.5–3.8 cm from the surface being steamed. If the tip is too far away, the steam water vapour may not be hot enough to kill all the bedbugs and eggs on such a surface. If the tip is too close, excess moisture may be injected into the treated material, and that can potentially lead to other problems – for example, facilitating the survival and increase of dust mite populations and creating an environment for the growth of surface molds.

4.5.4.5. Sticky monitors

Insect monitors with an adhesive layer on a flat cardboard backing are a simple means to detect many types of crawling insects. They have also been recommended to augment other techniques for increased control of some wandering spiders. Although bedbugs often get caught on such monitors, many recent reports from pest control technicians in North America have indicated these are not very effective at detecting much less increa- sing the level of control of small to moderate populations of bedbugs in rooms where other signs are obvious, where bugs are easily found by direct observation and where peo- ple are being bitten routinely. Based on this evidence, both the impact of such devices on the control of bedbugs and their reliability as a surveillance tool for the bugs are poor.

4.5.5. Pesticide applications

Currently, the exclusive use of non-insecticide control products and techniques is not effective or efficient enough to be practical. Even their use as a primary means for control- ling or eliminating an established bedbug population is ineffective. Still one of the most effective, practical and quickest ways to reduce the size of an established bedbug infes- tation is the use of a precisely placed but thorough application of a properly labelled, registered and adequately formulated residual insecticide. Effective control usually consists of applying interior sprays or dusts to surfaces that the bedbugs crawl over to reach the host, as well as applying them to cracks and crevices where they rest and hide. Microencapsulated formulations and dust formulations have a longer residual effect than other formulations. Also, both synergized and natural pyrethrins are used. Synergized pyrethrins not only show high lethal activity against the bugs, but they also show the abi- lity to flush them out, allowing quicker analysis of the infested area. Moreover, the addi- tion of natural pyrethrins at 0.1–0.2 vv to organophosphate, carbamate or microen- capsulated insecticide formulations will increase efficacy by irritating the bedbugs and initiating an excitatory effect that causes them to leave their hiding places, thereby increa- sing exposure to the fresh insecticide layer. Modified diatomaceous earths with hydrophobic surfaces can also be used to treat cracks and crevices. Retreatment, however, is essential and should be carried out at not less than two-week intervals until the population has been eradicated. Bedbugs 144 tly sealed containers can greatly reduce the availability of harbourage sites.

4.5.3.3. Mattress covers

Commercially available plastic covers, at least 0.8 mm thick and usually having a zippe- red edge, can completely encase a mattress or box spring and stop any bedbugs harbou- ring in either of them from further access to bite a host using that bed. Such covers were first developed and marketed as a measure to help reduce human exposure to HDM aller- gens that emanated from mattresses, but they can work well to isolate bedbugs within or keep them out of such items. If no such covers are readily available, any plastic of similar thickness and strength can be used to completely cover a mattress or box spring, and it can be sealed tightly shut with any durable, flexible tape, such as filament tape or duct tape Cooper Harlan, 2004.

4.5.4. Physical elimination techniques

Heat, cold and steam are used in physical techniques for eliminating bedbugs.

4.5.4.1. Heat

Heating infested rooms or whole buildings to temperatures of at least 45°C, the thermal death point of common bedbugs, has been used to try to control bedbugs since the early 1900s. For a heat treatment to be effective, it is critical to attain a high enough tempera- ture, low enough relative humidity and minimum length of time at those combined conditions. Some species of stored product pest beetles, which are considered to be very hard to kill, have been shown to be eliminated by exposure to a combination of 49–52°C and 20–30 relative humidity for 20–30 minutes Dosland, 2001. Heat treatments, however, do not prevent reinfestations, and bedbugs can reoccupy any site so treated immediately after temperatures return to ambient levels. Of concern in particular situa- tions, when using this technique for physically eliminating bedbugs, is the potential phy- sical distortion of structures or their contents, as well as flammability risks for some kinds of heat sources Usinger, 1966.

4.5.4.2. Cold

If bedbugs are kept cold enough long enough, exposure to cold temperatures can kill them. Bedbugs can tolerate –15°C for short periods and, if acclimated, they can survive at or below 0°C continuously for several days Usinger, 1966. Cold treatments of rooms or buildings to control bedbugs have not been well studied or used often, but freezing of furniture or other items within containers or chambers may be a practical alternative for limited infestations or to augment other control measures.

4.5.4.3. Controlled atmospheres

In a small series of very preliminary laboratory tests conducted by the German Federal Environmental Agency, all life stages of common bedbugs were reportedly killed within 24 hours or less by constant exposure to very high concentrations of carbon dioxide gas at ambient atmospheric pressure, but they were not affected very much by high concen- trations of nitrogen gas under those same conditions Herrmann et al., 1999. Further precise testing of such a strategy may be warranted. Public Health Significance of Urban Pests 147 control techniques to use against them. Several different active ingredients and formu- lations have been licensed and are currently used against bedbugs, and a variety of insec- ticide formulations and devices must be used to treat infested harbourages. As per label directions, applications of dust formulations should be used in electrical outlet boxes and in other places where it is desirable to use a minimum-risk, long-lasting insecticide.

4.5.5.5. Use of pest management products