Response of Eastern and Formosan Subterranean Termites (Isoptera: Rhinotermitidae) to Borate Dust and Soil Treatments
Workers of the termites Coptotermes formosanus Shiraki and Reticulitermes flavipes (Kollar) were topically treated with disodium octaborate tetrahydrate, a fine-grain zinc borate, or boric acid (+ 1%magnesium stearate) powder; they were also exposed to sand treated with borates in an indirect exposure tunneling assay. Dust treatment with boric acid powder caused the most rapid mortality, with application of all three powders causing 100% mortality within 15d. Treatment of 10-20% of the termite workers in test groups with borate dusts indicated that the toxicants are transmitted by grooming or trophallaxis (or both) to untreated individuals. However, less mortality occurred in groups of C. formosanus than in corresponding groups of R. flavipes workers when 10% of the workers were treated with disodium octaborate tetrahydrate or zinc borate powders. Both termite species readily penetrated sand containing 5,000, 10,000, or 15,000 ppm disodium octaborate tetrahydrate or zinc borate. In the 10-d test period, ~5,000 ppm (or greater) disodium octaborate tetra hydrate and 15,000 ppm zinc borate in the sand elicited high mortality (85-93%) in R. fla vipers. Responsesof C. formosanus workers were more variable. Only 10,000 and 15,000ppm zinc borate in the sand caused mortality (70-89%) significantly different from that in control groups. In both dust transmission and tunneling experiments, interspecific differences in grooming or tunneling behavior may cause reduced exposure of C. formosanus to the borates.