An architectural insecticide method based on insect traits

responsibility for wording of article: Akira Takashima (OIST)

What are architectural insecticide methods?

Physical technologies of insect control to protect against insect invasion of production facilities (factories) and logistic facilities (warehouses) are being developed. This technology is not based on using insecticides or similar chemical treatments in principle but based on architectural means such as designing structures and features when designing new buildings or restoring existing ones to protect against insect invasion. By considering insect behavioral traits and by intervening possible entrance pathways and breeding grounds in each room with appropriate countermeasures, it is possible to prevent or reduce insect invasions.

Suppressing propagation of insects inside buildings

Countermeasures against propagation of insects in buildings are not just a matter of the physical structure and equipment. Management and operation measures such as daily cleaning and monitoring of the inhabiting situation are also important.The role of architectural insect control countermeasures in combating propagation of insects is to provide physical structures that enable easier cleaning and monitoring. In particular, the junctions of walls and floors should be rounded, window frames should be angled, lighting should be embedded into the sealing and/or wall, and exposed horizontal pipes and rough wall surfaces are avoided inside rooms, thereby facilitating cleaning and eliminating potential insect hotbeds such as waste and dust reservoirs. The inside temperature and humidity are also major factors in propagation of insects. The development threshold temperature for insects inside buildings (the highest temperature at which the insects will not develop) ranges between approximately 10°C and 20°C. The optimal temperature for development is between 25°C and 30°C. Therefore, while considering the cost of temperature control, setting the air conditioning to a temperature of 15°C requiring relatively low energy should inhibit insect reproduction even in places only used for long-term storage of materials that insects could eat. Similarly, keeping the humidity lower than 60% inhibits the growth of molds that can serve as food for insects and will inhibit propagation of insects.

Countermeasures against insect invasion from outside

Architectural insecticide methods are largely dependent on countermeasures to prevent insect invasions from outside. Whether in a factory or in a warehouse, insect-trapping surveys have shown an overwhelming preponderance of chironomid and fungus gnat flies flying in from outside. Countermeasures against these invasions include keeping buildings airtight, regulating air pressure, and selecting suitable lighting methods and light sources. Modern factories and warehouses are airtight; hence drafty places have become uncommon. However, buildings need openings for people and goods to go in and out, and this is the main cause of insect invasions. Typical insect protection equipments for warehouse include dock shelters and high-speed sheet shutters. The dock shelters keep the entranceways covered by the truck during loading and unloading, and the interior stays airtight. High-speed sheet shutters protect against insects by ensuring rapid opening and closing and are suitable for precise open/close control essential for protection against insects. Protection against insects is improved if there is more than 1 door. Air can enter through ventilation openings; therefore it is essential to install fine mesh nets at the openings. The air flow in and out of the building affects insect invasions. It is easy to understand how insects can be transported in through airflow from outside the building. Air flowing out of the building can also facilitate insect invasions, given that some insects have propensity to fly upwind. Airflow is influenced by air pressure inside and outside the building. However, higher air pressure inside the building than outside appears to reduce insect invasions.

Attraction of insects to light

It is well known that insects have a positive phototaxis, and the choice of lighting regime and light source are a major factor to reduce insect invasions. Several light sources have been developed that exploit such a trait of insects.

Prospects of architectural insect control

The architectural insect control methodology is a practical technology field that has been recently established through human economic activity. It is highly expected that the insect control technology that does not rely on chemical reagents will be applicable to various other fields as an ecofriendly technology.

Further Reading

昆虫ミメティックス Insect Mimetics(2008),針山孝彦,下澤楯夫,pp.941-949

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