Comparative toxicity, residual nature and effect on respiration of boron compounds in a lower termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae)

Comparative toxicity of three boron compounds, boric acid (BA), disodium tetraborate decahydrate (DTD) and disodium octaborate tetrahydrate (DOT), against a lower termite, Coptotermes formosanus Shiraki, was investigated. Residual nature in termite body and the effect on respiration were also evaluated using boric acid as a substrate. Among three compounds BA performed best, showing the oral LD99 . 16 days value as approximately 930 mu g/g termite and 136 mu g/g termite (lethal accumulate). Approximately 20% of the ingested boric acid remained in the termite's body after more than 16 days. Ingestion of wood meal treated with BA at 20 kg/m(3) caused a 20% reduction of respiratory volumes, even when no mortality was observed. These results suggested that a relative amount of ingested boron compounds remained within the termite bodies and expressed their termiticidal performance by various physiological effects including obstruction of respiration.