**1. Introduction**

346 Pesticides in the Modern World - Risks and Benefits

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#### **1.1 Termite as pest insect**

Termites are insects that belong to Termitidae and from systematic point of view cockroaches are most closely-related to them. Although termites had been formed the independent order, Isoptera, recently they became a part of Blattodea (Inward et al., 2007). While cockroach is one of the most important household and hygiene pest insects all over the world, termite is also occupying a high position as a household pest insect. However their position is bit different from their closest relatives and is a structural pest which attacks and gives serious damage to wooden structures such as residences [c.f., in developing countries they are pests to trees and agricultural products (Constantino, 2002)]. In Japan, several hundred million dollars are spent annually for the prevention and control of termites (Yoshimura, 2001; Tsunoda, 2003). One thing to be addressed here is that termites are very important decomposers of cellulose in the ecosystem. They become pest insects when their habitats overlap those of humans.

Fig. 1. Left: workers and soldiers of *Coptotermes formosanus* in their nest. Right: Damage on a residential structure caused by foraging termites of *C*. *formosanus*

Termites are eusocial insects similarly as Hymenopterous insects, like ants and wasps, which are taxonomically distantly-related groups. They usually build up queen-and-king-centered

Colony Elimination of Subterranean Termites by Bait Application

species in Japan were used for the studies.

Fig. 2. Chemical structure of bistrifluron

workers in the laboratory (Kubota et al., 2006).

interval to determine the change in mortality over time.

intervals after termites were released. Five replications were made.

**2.1 Evaluation methods** 

**2.2 Speed of action** 

**2. Termiticidal activity of bistrifluron and its speed of action** 

**1.3 Bistrifluron** 

Using Benzoylphenylurea Compounds, with Special Reference to Bistrifluron 349

Bistrifluron (Fig. 2) is one of BPUs (Kim et al., 2000), therefore it was expected to show good efficacy in terms of colony elimination of subterranean termites. Author conducted several laboratory studies to evaluate inseciticidal efficacy of the compound against subterranean termites in order to examine how baiting with BPUs bring about colony elimination of termites. *C. formosanus* and *Reticulitermes speratus* (Kolbe) which are the most important pest

In order to quantitatively evaluate feeding toxicity of bistrifluron against termite, no-choice and two-choice feeding tests with filter paper baits were conducted with *C. formosanus*

In the no-choice feeding test, filter paper disks treated with 0.005, 0.05, 0.5 and 5.0% (w/w) of bistrifluron were air-dried and weighed. Each disk was placed in a small plastic cup (ca. 14 ml) with small entry holes to allow termite access. Plastic cups were then put into separate plastic containers (200 ml) and each container retaining 100 of *C. formosanus* workers. The bottom of this larger container was covered with 2-3 mm of plaster and had several small holes made in the base. Assembled units were placed on a damp cotton pad in an incubation chamber so that termites could uptake water through the plaster. Five units were prepared for toxic baits and untreated controls. The units were maintained under appropriate condition for 12 weeks. Dead or moribund termites were counted at given

In the two-choice feeding tests, Filter paper disks were treated with 0.5% (w/w) of bistrifluron. The test container was a plastic Petri dish (140 mm in diameter) with approximately 5 mmthick agar [4% (w/w)] on the bottom. Four wells (35 mm in diameter) were made through the agar and plugged by two treated and two untreated disks. One hundred termites were introduced before the dish was covered with a lid and sealed with parafilm. Units were kept under appropriate condition. Mortality and weight of disks consumed were checked at given

In the no-choice test, mortality increases significantly faster as bistrifluron concentration were higher (Fig. 3). When termites were exposed to 0.5% bistrifluron (possible concentration in a commercial product), there had been no significant increase in mortality

colonies. Thousands to millions of worker termites are usually deployed in each colony. They are systematically mobilized to attack and feed wooden materials, therefore sometimes give critical damages to wooden structures. Among them, economically the most important group in temperate and tropical regions is Rhinotermitidae which includes genera *Coptotermes* and *Reticulitermes*. Termites belonging to Rhinotermitidae are 'subterranean termites' as they build their nests in the ground. Since they come on underground tunnel and often invade through underfloor space of structures, few people are aware of them until their houses are assaulted. *Coptotermes* and *Reticulitermes* termites widely occur in human habitat and are seriously harmful to structures. *Coptotermes* termites, like *Coptotermes formosanus* Shiraki, *Coptotermes gestroi* (Wasmann), *Coptotermes acinaciformis* (Froggatt) and so on, build huge colonies and extremely problematic species around the Pacific countries (Fig. 1).
