Survival and feeding of subterranean termites, Reticulitermes spp., in three relative humidity regimes

Termites caused $577 million worth of damage in the United States in 1983, and approximately $1.5 billion is spent for control of termites each year. Previous research has dealt with direct control of termites, but little has been done to determine the effects of relative humidity and wood moisture on termites isolated in a wooden structure.

Research was conducted to determine the effects of soil access or no-soil access in three relative humidity regimes (90 to 100%, 50 to 60%, and 30 to 40%) on survival and feeding of the eastern subterranean termite, Reticulitermes flavipes (Kollar), and a related species, R. virginicus Banks. Wood moisture content in southern yellow pine (Pinus sp.) framing was measured, and termite damage ratings were determined for weathered pine blocks and strips in each regime.

Termite survival in simulated wall voids in which termites were excluded from or allowed access to soil was determined. Colony survival at the highest humidity (90 to 100%) was full term (45 days) with 50% or more of the individuals surviving at the end of the test. The medium humidity (50 to 60%) had a greater contrast in termite survival between soil access and no-soil access voids than the lowest and highest relative humidities. At the low relative humidity (30 to 40%) significant differences in survival occurred between the soil access and no-soil access voids, but termite survival time was shortest overall.

Wood moisture content in pine frames was measured every other day at each relative humidity. There were no significant differences in wood moisture content between soil access and no-soil access frames within a single relative humidity level. However, differences were detected among the relative humidity levels, as wood moisture content was significantly greater at the highest relative humidity than at the medium and low humidities.

Wood weight loss and damage ratings were affected by termite survival, which was a function of relative humidity. There was a general trend of significantly higher wood loss and damage rating values for the highest relative humidity compared with the medium and low humidities.