Laboratory and Field Evaluations of Selected Chemical Treatments for Control of Drywood Termites (Isoptera: Kalotermitidae)

Abstract

A 1-m board bioassay was used to assess the efficacy of spinosad, disodium octaborate tetrahydrate (DOT), calcium arsenate, and chlorpyrifos on the mortality and fecal pellet production of 2 drywood termite species, Incisitermes snyderi (Light) and Cryptotermes brevis (Walker), under unforced exposure and simulated field conditions. Spinosad suspension concentrate at 2,300 or 5,000 ppm, 35% calcium arsenate, and chlorpyrifos aerosol at 5,000 ppm were more toxic and reduced pellet production compared with DOT treatments at 4 wk. Of DOT treatments, only 98% dust caused higher mortality than controls at 8 wk. Spinosad suspension concentrate and chlorpyrifos had an effect on termite location in bioassay boards. Acoustic emissions activity of 55 C. brevis infestations in 2 buildings was determined before intragallery injection of liquids and dusts tested above, with the exception of arsenate dust, and surface application of 10% DOT. After treatment, acoustic emission activity was recorded for each infestation at 1, 2, 3, 5, 8, and 12 mo. At 4 mo, one building was fumigated with sulfuryl fluoride. Posttreatment readings taken 3 mo or earlier for infestations treated with spinosad suspension concentrate, chlorpyrifos, and DOT surface showed reductions in acoustic emission activity. Only spinosad SC treatment yielded significant acoustic emission reductions at 5 mo or later. Results suggest that chemical toxicity, formulation, and application method, as well as drywood termite behavior and gallery system architecture, influenced the performance of local chemical treatments. Sulfuryl fluoride fumigation resulted in cessation of acoustic emission activity in all colonies monitored in the fumigated building.