Alternative strategies Cockroach control: sanitation practices

Public Health Significance of Urban Pests 71 These indoor perimeter applications are designed to provide preventive control, and they should only be used when visual monitoring or traps indicate the presence of cockroaches. Special precautions should be taken to reduce the likelihood of people, pets and non-tar- get organisms being exposed.

2.6.2.4. Alternative strategies

There will always be situations and sensitive areas where the use of insecticides is unfea- sible, impractical or prohibited. Cockroach infestations in equipment such as cash regis- ters, computers, televisions and radios or in such places as museums, health care facilities, airplanes, ships and vehicles might be difficult to treat with conventional strategies. Alternative approaches have been successful, but have been used on a limited basis. For use in museums, a simple procedure that uses special polyester bags, nitrogen gas and an oxygen scavenger to produce anoxic atmospheres less than 0.1 oxygen readily kills cockroaches Rust et al., 1996. Adult American, German, and brownbanded coc- kroaches are killed with 6-hour exposures, whereas nymphs of all three species are killed within 24 hours. The most resistant stage is the ootheca. The American, German, and brownbanded cockroach oothecae require exposures of 120, 24, and 72 hours, respectively, to produce 100 mortality. Most household insect pests are extremely sensitive to high temperatures. At 51.7ºC, a 30-minute exposure kills 100 of adult male German cockroaches Rust Reierson, 1998. In field studies, it was possible to control German cockroaches by heating food- handling areas in buildings to 46ºC for 45 minutes Zeichner et al., 1996. The heat treat- ment successfully reduced chemical treatments by 60. Even though it was expensive, the treatment was considered a success because of the repeated failures with conventional chemical controls prior to heating. 2.7. Insecticide resistance 2.7.1. Physiological insecticide resistance As long as insecticides are an integral part of pest management programmes, the poten- tial for development of physiological resistance to them will be significant, especially for the control of German cockroaches. Also, insecticide resistance in other cockroach spe- cies has appeared in recent reports. German cockroaches have developed resistance to many of the organophosphates, carbamates and pyrethroids extensively used against them Cochran, 1995. Resistance to some insecticides, such as pyrethrins, bendiocarb, diazi- non and chlorpyrifos, was widespread in 1989, but resistance to such pyrethroids as per- methrin, cyfluthrin and cypermethrin was found in only a few strains. Of 30 strains col- lected in the field from three continents, 15 had a more than twofold resistance to pyrethroids and 12 were also resistant to chlorpyrifos and propoxur Hemingway et al., 1993. By 1998, at least one gene for resistance to cypermethrin was common in strains col- lected in the field. Of 57 strains in which the gene frequencies were determined, 31 were resistant Cochran, 1998. A full range of resistance mechanisms, including esterase- and Cockroaches 70 ger. Resurgence of cockroaches appeared to result from a loss of bait and not degradation of active ingredient Reierson et al., 2005. Baits are an important component of cockroach IPM programmes. However, a common misconception is that the use of baits alone is IPM. Nothing could be farther from the truth. Effective IPM involves a systematic approach and process see Chapter 15 of this report.

2.6.2.2. Crack-and-crevice treatments

The method of applying insecticides greatly affects its bioavailability to pests and people Rust, 1995, 2001. Applications of small amounts of non-repellent insecticides to cracks and crevices are effective against such insects as cockroaches and silverfish, because these insects prefer to hide in small dark spaces. Non-repellent insecticides are more likely to be encountered by cockroaches than repellent insecticides that flush them out of hiding areas. Small crevices are ideal sites to place gels baits, dusts and liquid sprays. Crack-and-crevice treatments will quickly reduce the numbers of foraging cockroaches, but will not eliminate breeding populations in voids and outdoor sites. These spot treat- ments are most effective when applied in conjunction with structural repairs, void treat- ments and sanitation. Spot treatments to cracks and crevices reduce the amount of insec- ticide applied indoors and also reduce the likelihood of exposing people and pets to insecticides Rust, 2001. These treatments are designed to be preventive and should only be made when visual monitoring or traps indicate the presence of cockroaches.

2.6.2.3 General surface treatments

Indoors, baiting and other less pervasive methods have largely replaced the use of spot, baseboard and surface sprays. Nevertheless, perimeter and spot treatments have a place in IPM, especially in treating peridomestic species outdoors, where the application of bait, structural modifications or built-in controls is problematic. The activity of insecticides against eight pest species, including American, oriental and smokybrown cockroaches, is in order of most active to least active as follows: pyrethroid, carbamate and organo- phosphate Valles, Koehler Brenner, 1999. Encapsulated diazinon and chlorpyrifos applied to perimeters of homes and in crawl spaces provided about 95 reductions of oriental cockroaches for at least 12 weeks Thoms Robinson, 1987a. The use of IGRs as surface sprays or in total release aerosols has always been of interest, because of their low toxicity to mammalians. However, because of their modest efficacy against cockroaches, they have never gained acceptance. In a recent study, noviflumuron sprays applied in infested apartments provided up to 90 reductions of German coc- kroaches at four weeks post-treatment Ameen et al., 2005. Also, in the control of German cockroaches, residual sprays of chlorfenapyr provided 80 reductions in infested apartments at eight weeks post-treatment Ameen, Kaakeh Bennett, 2000. Chlorfenapyr is a pro-insecticide – that is, it is only activated to its toxic form in the cockroach’s body – that shows promise as an alternative treatment for field strains with high levels of mixed function oxidase, resulting in insecticide resistance.