Development and thermal activity thresholds of European mirid predatory bugs

Generalist predators belonging to Dicyphini (Hemiptera: Miridae) play an important role in pest control in vegetable crops. Temperature is one the most important factors affecting their efficacy as biological control agents (BCAs) and a better understanding of temperature effects can help to select the best performing species for certain climatic conditions. In this study we assessed the thermal requirements of six dicyphine species: Dicyphus bolivari (2 different strains), Dicyphus eckerleini, Dicyphus errans, Dicyphus flavoviridis, Nesidiocoris tenuis and Macrolophus pygmaeus. Two experimental methods were used: one static, by recording the developmental times at six temperatures (15–40 °C) and one dynamic, by determining low and high temperature thresholds for movement. Based on the results of both methods we identified two groups: N. tenuis, M. pygmaeus and D. bolivari showed the best performance at high temperatures and the species D. errans, D. eckerleini and D. flavoviridis were most active at low temperatures. Dicyphus bolivari and N. tenuis were the only species able to reach adulthood at the constant temperature of 35 °C. At low temperatures, D. eckerleini and D. errans were the only species still able to walk below 0 °C. The species less vulnerable for lower temperatures were more vulnerable for higher temperatures and viceversa. Among the tested species, the larger sized species seem to be better adapted to lower temperature and the smaller sized species better to higher temperatures. Females and males in all species differed in their cold and heat tolerance. Males were in general better adapted to higher temperatures and females better adapted to lower temperatures.