Horizontal transfer of boron by the Formosan subterranean termite (Coptotermes formosanus Shiraki) after feeding on treated wood

The goal of the present study was to determine whether Coptotermes formosanus Shiraki workers exposed to boron-treated wood were capable of transferring quantifiable amounts of boron to non-exposed nestmates. This effect is called horizontal transfer. Borates are not repellent to termites, nor do they cause rapid mortality, making them excellent candidates for the study of horizontal transfer. In the present study, C. formosanus workers were collected from field colonies maintained in Honolulu, Hawaii and dyed with Sudan Red 7B over a 7-day period. These termites then underwent a 3-day exposure period to one of two types of composite board, either an experimental formulation of zinc borate and anhydrous boric acid or an untreated composite board. Treated termites were placed with an equal number of untreated termites for either 5 or 10 days; sham-dyed donors and recipients were used to control for possible effects of the dye. Horizontal transmission of boron and toxic effects were assessed based on termite wet weight, percent survival, and boron content. Horizontal transfer of boron was noted at both 5 and 10 days over those levels reported in untreated, field-caught termites from the same colony (ca. 7 mg boron g-1 termites). After 5 days, boron content was elevated in both dyed donor and recipient termites (ca. 92 and 38 mg boron g-1 dyed termites, respectively), as well as in undyed donors and recipients (ca. 84 and 30 mg boron g-1 undyed termites). The same pattern was observed after 10 days in both dyed donor and recipient termites (ca. 61 and 46 mg boron g-1, respectively) and undyed donor and recipient termites (59 and 24 mg boron g-1, respectively). Increased boron content of recipient termites after exposure to donor termites (fed on treated wood) demonstrated horizontal transfer of boron.