**6. Conclusions**

358 Pesticides in the Modern World - Risks and Benefits

treated and untreated). Because no forager was present at site 1 (treated bait added on 25 September) on sampling dates from 26 October to 30 November, all baits were replaced with new ones on 20 November as previously noted: toxic baits were added at sites 2 and 3 and a blank bait was added at site 1. Foraging termites were seen at site 1 on 30 December, and foraging termites were observed at site 2. One possible explanation for the decreased foraging population and disappearance of foragers from site 1 is feeding deterrence by bistrifluron, as previously suggested in the two-choice test described in section 2.2. Although it is unclear why foragers came back to the toxic bait at site 2, the shuffle of treated bait sites might lead to reinfestation of the treated bait by foragers at site 2 where termites previously fed on untreated bait. Dead workers and soldiers were found at site 1 and site 2 several days after the last collection (31 January 2008), and no live termite was present at these sites. Author concluded that the colony was eliminated because no live termites were found over half a year after application of toxic baits. Although the current study demonstrated that *C. formosanus* colonies could be eliminated by application of bistrifluron,

Bistrifluron amounts recovered from each termites collected from each site are shown in Fig. 10. The recovered amounts of bistrifluron ranged from 101 to 1026 ng/termite when five foragers were collected from site 1 (with toxic bait) on 28 September (day 3) and 1 October (day 7). On the other hand, when blank baits were present at sites 2 and 3, only two of 17 foragers contained bistrifluron, and the quantities detected were small (45 and 57 ng/termite). Between 10 October and 30 November 2007 (toxic bait at site 1 and blank baits at sites 2 and 3), bistrifluron was detected from seven foragers collected from site 1, and the amounts ranged from 31 – 477 ng/termite. During this same period, analyses of 28 foraging workers from sites 2 and 3 indicated that 17 termites contained bistrifluron (22 – 196 ng/termite) and 11 termites did not. These results appear to demonstrate that up to a few hundred milligrams of

Because much smaller amounts of bistrifluron were recovered from workers collected at sites 2 and 3 than site 1, it is uncertain whether those workers were donors or recipients of bistrifluron among colony members. If they were recipients, they received some bistrifluron from donors that originally took bistrifluron at site 1. This was quite possible because only a small portion of materials taken up by donors would be transferred to recipients (Sùarez & Thorne 2000; Haagsma & Rust 2005; Buczkowski et al., 2007). If they were donors, they consumed bistrifluron at site 1 and were caught at sites 2 or 3 after losing some portion of the bistrifluron through trophallaxis and metabolism. Unfortunately, distinguishing between donors and recipients will be difficult until foraging behaviour of termites is better understood: after feeding at one site, whether do foragers feed at other sites on their way

the results clearly supported the importance of placement of baits.

**5.4 Manner of the uptake of bait toxicant by foraging termites** 

bistrifluron was taken up by an individual worker through foraging activities.

back to the nest? And how frequently do they go the rounds of their feeding sites?

were killed by the insecticidal effect of noviflumuron (Su, 2005).

Analyses of eight termites collected on 31 January 2008 (several days before colony elimination) revealed that these termites consumed sufficient amounts of bistrifluron (483 – 1380 ng/termite) to cause death by 31 January 2008. Because of the lack of data describing the temporal change in the quantity of bistrifluron taken up by termites during this period, we were unable to delineate how bistrifluron spread within the colony, although the results clearly showed that almost all foragers acquired a lethal dose of bistrifluron. Slow mortality will allow the foragers to move too far to identify source of toxin and is therefore essential if the bait is to eliminate colonies of subterranean termites like *C. formosanus*. Workers of *C. formosanus* exposed to 0.5% (w/w) noviflumuron bait could move as far as 50 m before they It can be concluded as below by a series of experiments:


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