Wood moisture effects on Formosan termite mortality and water loss

The subterranean termite, Coptotermes formosanus (Shiraki) is the most aggressive and destructive termite species found in the United States. Although it normally forms colonies in the soil, it is found in aerial infestations. According to the literature, termites will survive when the relative humidity of the environment is near 100% because it prevents cuticular evaporation. It has also been stated that when wood is at 15% moisture, it can support subterranean termite activity. This experiment looked at the mortality rate and water weight loss in C. formosanus at different levels of wood moisture content (MC). Blocks of southern yellow pine at 5 to 35% wood moisture with no soil contact were set up for destructive sampling at 1, 2, 3, 5, 7, 10 and 14 days. Mortality decreased as levels of wood MC increased however long term survival did not occur until wood was above its saturation level. A 15% MC was insufficient for termite survival and caused 100% termite mortality within 7 days. Termite mortality was the lowest at levels of wood moisture above the saturation level showing that termites need free water in order to have long term survival. When the relative humidity of the surrounding environment around the wood was 100%, termites still lost water. Relative humidity and moisture content of the wood are key factors in termite survival, however, in order for aerial infestations to occur, wood needs to be at levels >25-30% MC.