Higher temperatures reduce the efficacy of a key biocontrol parasitoid

Abstract

A primary facet of climate change is an increase in average temperatures which can have immense consequences for ectotherms, organisms that cannot physiologically regulate their own body temperatures, such as insects. Moreover, thermal stress can influence species interactions across trophic levels, especially if members of different trophic levels show differential responses. In agricultural systems, parasitoids are frequently used as biocontrol agents to reduce crop damage by regulating populations of insect herbivores, but climate change can potentially threaten this ecosystem service. In this study, we investigated the effects of diurnally fluctuating temperature regimes (average treatment temperatures = 23 °C, 25 °C, 27 °C) on the relationship between the common agricultural pest Plutella xylostella and its larval parasitoid Diadegma insulare. We found that at higher temperatures, both the host and the parasitoid developed faster. Host survival was not influenced by temperature, but higher temperatures resulted in increased parasitoid mortality in the pupal stage. Realized parasitism rates were also significantly decreased at higher temperatures, suggesting that D. insulare may become a less efficient biocontrol agent of P. xylostella as temperatures continue to increase.