A case for adopting a standardized protocol of field and laboratory bioassays to evaluate a potential soil termiticide

The rationale for adopting a new approach to the field testing of potential soil termiticides is advocated on the grounds that current testing methods are limited to termite bioassays and do not address quantitatively the persistence and bioavailability of soil termiticides to foraging subterranean termites over time and in different soil types. Furthermore, the present testing regimes assume field situations of uniform high termite hazard across field sites. Our testing procedures require the random sampling of soil cores from test soil pads (500 x 500 mm) at several geographically different locations. The soil cores from treated and untreated soil pads are returned to the laboratory and half of the samples chemically analyzed using a chromatographic method (HPLC) examined for each year of test period. The bioavailability of termiticide residues in the remaining soil samples are evaluated by tunnelling bioassays using the field collected subterranean termites, Coptotermes acinaciformis (Froggatt). Both tunnelling distance and mortality are used as indicators of termiticide activity and availability. This paper compares the traditional soil test methods with our new approach, which addresses the problems of security with longevity of test, variability of termite hazard levels at different field sites, and a practical method for managing variables in assessing potential soil termiticides. Importantly, this technique prevents the direct destruction of natural populations of subterranean termites or the indirect contamination by contact from soil residues of termiticides applied in and around active termite colonies.