Determination of temperature and relative humidity combinations that are sub-lethal to bed bugs

Bed bugs (Cimex lectularius) are obligate blood feeders and a global pest, whose survival is significantly influenced by environmental factors, like temperature and relative humidity (RH). Yet, bed bugs are well-adapted to survive in dry environments as they are resistant to desiccation. However, sub-lethal heat exposure impacts their feeding, reproduction, and development. This study aims to determine specific temperature and humidity combinations that induce sub-lethal effects, to understand how different humidity levels influence heat-induced mortality. Harlan bed bugs were exposed to various temperatures (25℃, 37℃, 38℃, 39℃, and 40℃) and RH levels (10% (low), 45% (standard), 90% (high)), in a temperature-controlled incubator, for 14 days and mortality was checked daily. This study found that a temperature-RH combination of 40°C and 90% resulted in the highest bedbug mortality within a day, and 40°C at 10% RH achieved 100% mortality within 5 days. At 38°C, lower RH led to quicker mortality. Normal humidity conditions at all temperatures showed similar rates of bed bug mortality at different temperatures. These findings suggest that low humidity is more important for inducing bed bug sub-lethal mortality at 38°C and below. However, as lethal temperatures are approached, higher humidity caused mortality at a faster rate than low humidity, indicating that heat index plays an important role in heat-induced bed bug mortality. Identifying temperature and RH combinations that are sub-lethal (e.g., 38℃, 10%RH) to bed bugs enables future studies that examine what management strategies could be improved by heat.