Value of observational data in bioassays for evaluating bait efficacy against subterranean termites (Isoptera : Rhinotermitidae)

A novel method is presented for determining bait removal and acceptance of up to nine choices under laboratory conditions by the Formosan subterranean termite, Coptotermes formosanus Shiraki. Data from a study using this meth od showed that estimated bait removal and bait mass loss data were correlat ed (r=0.694; P <0.0001), indicating the value of periodic bait removal esti mates during choice studies. We also provide data from a two-choice test wh ich allows collection of standard data such as mortality and wood mass loss at the end of the experiment, but also gives information on the daily prog ression of bait matrix removal by termites. We examined this method with C. formosanus using powdered cellulose bait matrices containing two rates eac h of zinc borate hydrate (ZB) or disodium octaborate tetrahydrate (DOT) pai red with Ponderosa pine blocks. In the example trial, 2% DOT cellulose bait s were removed by termites significantly more than all other baits during t he first week of the experiment (P = 0.001), and overall mortality was sign ificantly greater with DOT baits than with ZB or blank controls (P < 0.0001 ). Wood mass loss was significantly lower for those blocks paired with the DOT baits than for those paired with controls or ZB baits (P < 0.0001). No significant difference was found between either wood mass loss or mortality of termites exposed to 1% or 2% DOT bait. Thus by using the daily bait rem oval estimates, differences in rate performance between the two DOT baits c ould be assessed that were not apparent from standard quantitative data col lected at the end of the experiment.