Disodium octaborate tetrahydrate treatments to slash pine for protection against Formosan subterranean termite and eastern subterranean termite (Isoptera: Rhineotermitidae)

Minimum retentions of disodium octaborate tetrahydrate (DOT) needed in slash pine, Pinus elliottii Engelm. variety elliottii, wood to provide maximum protection against 2 species of subterranean termites were determined in choice and no-choice laboratory tests. Efficacy criteria for DOT were greater than or equal to 90% termite mortality and less than or equal to 5% loss in weight of treated wooden blocks. For termites fed only DOT-treated wood, 0.10 and 0.30% boric acid equivalent (BAE, percentage of boric acid based on dry weight of wood, assuming all boron is present as boric acid) protected wood from the eastern subterranean termite, Reticulitermes flavipes (Kollar), and Formosan subterranean termite, Coptotermes formosanus Shiraki, respectively. When termites had a choice between treated or nontreated wooden blocks, 0.30% BAE protected wood from R. flavipes, but the highest retention tested, 0.54% BAE, was not effective against C. formosanus. In a nonleaching field study where wooden blocks were not in contact with soil or exposed to rain, a BAE of 0.30% protected the wood from naturally occurring Reticulitermes sp. for 18 mo. In wooden structures under constant pressure from subterranean termites, concentrations 0.54% BAE may be required to protect wood, especially against C. formosanus