Laboratory evaluation of high temperatures to control Cryptotermes brevis (Isoptera: Kalotermitidae)

Rates of thermal increase as low as 0.04 degrees C/min were measured in large wooden members during high-temperature termite control treatments. It was hypothesized that slow rates of thermal increase might promote termite acclimation to high-treatment temperatures. However, in laboratory studies, 46 and 49 degrees C core temperatures were 100% lethal to Cryptotermes brevis (Walker) nymphs in wooden blocks (13.5 by 13.5 cm) in both 30- and 60-min exposures, whereas equal durations at 46 degrees C were between 30 and 70% effective in 8.5 by 8.5-cm blocks. Rates of temperature increase were slower in larger blocks and were correlated positively with observed thermal tolerance. The negative effect of low rates of increase may be the result of the cumulative effects of sublethal stresses. It was concluded that the commercially recommended target wood-core temperature of 54.4 degrees C is sufficient for controlling C. brevis in large timbers. However, priority should be given to achieving lethal temperatures in worst-case areas as opposed to increasing treatment temperatures because higher temperatures may not result in better control and may increase the risk of heat damage to property within the treated structure