Mortality patterns in Coptotermes gestroi (Blattodea: Rhinotermitidae) following horizontal transfer of nonrepellent and repellent insecticides: effects of donor:recipient ratio and exposure time.

The donor: recipient ratio and the time of donor exposure to termiticide required for maximal toxicant transfer among termites are crucial information for the development of termite management plans. Most of the available information on termiticide toxicity came from temperate zonal termite species, whereas little is known about tropical Asian species. In this study, mortality patterns of recipient termites, Coptotermes gestroi (Wasmann) subjected to seven formulated insecticide exposures under different donor exposure times and donor: recipient ratios were examined. For fipronil, lethal transfer was not affected by donor exposure time but was affected by the mixing ratio. The moderate-to-less toxic termiticides (imidacloprid, indoxacarb, bifenthrin, chlorfenapyr, and chlorantraniliprole) required long exposure time and a high mixing ratio to ensure maximal uptake by recipient workers compared with fipronil. For chlorantraniliprole and chlorfenapyr, donors must constitute > 30% of the donor-recipient mixture to achieve 100% mortality of the recipient workers. Among the termiticides tested, cyantraniliprole was the most fast-killing insecticide against C. gestroi. The potential of lethal transfer among recipient termites does not necessarily require both high donor exposure time and a high mixing ratio, but the toxicity of a given termiticide against termites must be factored in to achieve colony elimination.

Ability of field populations of Coptotermes spp., Reticulitermes flavipes, and Mastotermes darwiniensis (Isoptera: Rhinotermitidae; Mastotermitidae) to damage plastic cable sheathings.

A comparative field study was conducted to evaluate the ability of subterranean termites to damage a set of four different plastic materials (cable sheathings) exposed below- and above-ground. Eight pest species from six countries were included, viz., Coptotermes formosanus (Shiraki) in China, Japan, and the United States; Coptotermes gestroi (Wasmann) in Thailand and Malaysia; Coptotermes curvignathus (Holmgren) and Coptotermes kalshoveni (Kemner) in Malaysia; Coptotermes acinaciformis (Froggatt) with two forms of the species complex and Mastotermes darwiniensis (Froggatt) in Australia; and Reticulitermes flavipes (Kollar) in the United States. Termite species were separated into four tiers relative to decreasing ability to damage plastics. The first tier, most damaging, included C. acinaciformis, mound-building form, and M. darwiniensis, both from tropical Australia. The second tier included C. acinaciformis, tree-nesting form, from temperate Australia and C. kalshoveni from Southeast Asia. The third tier included C. curcignathus and C. gestroi from Southeast Asia and C. formosanus from China, Japan, and the United States, whereas the fourth tier included only R. flavipes, which caused no damage. A consequence of these results is that plastics considered resistant to termite damage in some locations will not be so in others because of differences in the termite fauna, for example, resistant plastics from the United States and Japan will require further testing in Southeast Asia and Australia. However, plastics considered resistant in Australia will be resistant in all other locations.

Toxicity and horizontal transfer of chlorantraniliprole against the Asian subterranean termite Coptotermes gestroi (Wasmann): effects of donor:recipient ratio, exposure duration and soil type.

BACKGROUND: The effectiveness of chlorantraniliprole and other insecticides (bifenthrin, fipronil, indoxacarb, imidacloprid and chlorfenapyr) were tested against Coptotermes gestroi (Wasmann). Four experiments were conducted: a topical bioassay, a horizontal transfer study, an insecticide bioavailability test and a feeding bioassay. RESULTS: The topical bioassay showed that chlorantraniliprole was significantly less active to C. gestroi at 24 h post-treatment compared with the other insecticides tested. Nevertheless, it is likely that a lesser amount of chlorantraniliprole was required to cause 50% mortality of C. gestroi at 7 and 14 days post-treatment. The exposure duration and donor:recipient ratio affect the mortality of recipient termites. Mortality after exposure to chlorantraniliprole in sandy clay was significantly lower than in sand; however, by 14 days, > 90% of donor and recipient termites died in both substrates, irrespective of concentration. Fipronil and imidacloprid showed faster action, and high to moderate toxicity to C. gestroi. Termite workers also ceased to feed after exposure for 1 h to 50 mg kg(-1) chlorantraniliprole-treated sandy clay. CONCLUSION: Chlorantraniliprole demonstrated delayed toxicity at the lowest label rate (50 mg kg(-1) ) in sandy clay. Its slow action will enable greater transfer of toxicant between nestmates, while feeding cessation will promote greater social interaction between healthy and exposed termites.