Abstract
Two subterranean termite species were subjected to combinations of six temperatures (10°, 15°, 20°, 25°, 30°, or 35°C) and five relative humidities (RH) (55, 65, 75, 85, or 99%) to determine optimum conditions for survival. When small groups of the Formosan subterranean termite Coptotermes formosanus Shiraki or the eastern subterranean termite Reticulitermes flavipes (Kollar) were exposed to all 30 combinations of temperature and RH, survival times were significantly influenced by temperature, RH, and their interaction. For both species, survival times were longest at low temperatures and high RH. Maximum survival of small groups of C. formosanus and R. flavipes workers and soldiers occurred at the combination of 10°C and 99% RH C (LT50= 28.2 d, LT50 = 18.1 d, respectively). Survival of paired C. formosanus dealates was evaluated at combinations of 20°, 25°, or 30°C and 55, 65, 75, 85, or 99% RH. Survival was strongly influenced by temperature and humidity. Longest survival times until 50% mortality occurred at 99% RH and 20° or 25°C (LT50= 2.5 d, LT50 = 3.0 d, respectively). At all temperatures, mortality occurred too quickly for LT50 values to be determined when RH was 55% or 65%.
Highlights
Temperature and moisture are key factors affecting termite survival, activity, and geographic distribution
Sponsler and Appel (1990) found that nest materials from two subterranean termite species had moisture contents ranging from 16.3% – 67.7% and interstitial spaces near saturated relative humidities (RH) levels
Survival times increased with relative humidity (Figs. 1-6, Table 1)
Summary
Temperature and moisture are key factors affecting termite survival, activity, and geographic distribution. Effects of soil moisture on feeding and tunneling activity have been extensively studied (Su and Puche 2003, Arab and Costa-Leonardo 2005, Green et al 2005, McManamy et al 2008). Sponsler and Appel (1990) found that nest materials from two subterranean termite species had moisture contents ranging from 16.3% – 67.7% and interstitial spaces near saturated RH levels. Humidity may indirectly influence subterranean termite success by affecting the ability of soil and wood to retain moisture. Daily fluctuations in temperature and relative humidity do not have much affect on wood moisture. Inside homes, the relative humidity of outdoor air is altered by heating and cooling, resulting in seasonal changes in wood moisture content. Humidity and temperature can affect the survival of alates, dealates, aerial populations, and colony fragments transported to new locations, having important implications for termite dispersal
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