Improving methods to measure critical thermal limits in phloem‐feeding pest insects

Abstract

International audienceThe ability to accurately assess thermal tolerance in the laboratory without compromising ecological relevance is essential to predict the impacts of global climate change on phytophagous pest insects such as the phloem-feeding aphids. One method to study thermal tolerance employs a temperature-controlled column to measure critical thermal limits. However, assessments are commonly made with little relation to the natural environment of the study species. This study measured critical thermal minima (CTmin) for three cereal aphids – Sitobion avenae (Fabricius), Metopolophium dirhodum (Walker), and Rhopalosiphum padi (L.) (all Hemiptera: Aphididae) – in the absence and presence of host plant material to determine the best experimental design. Results revealed that CTmin measured in the presence of the host plant was significantly lower, suggesting that performing the measurement in the absence of the host plant could result in an underestimation of insect thermal tolerance. In addition, the study highlights the importance of understanding how an insect interacts with its environment, as this can reveal behavioural variation integral to differential survival at unfavourable temperature

Comparative assessment of the thermal tolerance of spotted stemborer, Chilo partellus (Lepidoptera: Crambidae) and its larval parasitoid, Cotesia sesamiae (Hymenoptera: Braconidae)

“…The thermal tolerance traits commonly measured in ectotherms vary and may include both lethal and sublethal tests (see Sinclair et al, 2015). Lethal tests that result in the death of the insects include lethal temperature determination, time to death at set temperatures and supercooling points, dependent on insect freezing strategy (Formby et al, 2013;Alford et al, 2016). Sublethal tests include determination of critical thermal limits (CTLs) (i.e., the onset of extreme conditions, beyond which an insect's activity is compromised), time to heat knock-down and/or recovery after chill-coma Alford et al, 2016).…”

“…Lethal tests that result in the death of the insects include lethal temperature determination, time to death at set temperatures and supercooling points, dependent on insect freezing strategy (Formby et al, 2013;Alford et al, 2016). Sublethal tests include determination of critical thermal limits (CTLs) (i.e., the onset of extreme conditions, beyond which an insect's activity is compromised), time to heat knock-down and/or recovery after chill-coma Alford et al, 2016). CTLs are considered more ecologically relevant as temperature can be raised or cooled using rates that mimic field conditions (Rezende et al, 2011;Alford et al, 2016;Verberk et al, 2016).…”

“…Sublethal tests include determination of critical thermal limits (CTLs) (i.e., the onset of extreme conditions, beyond which an insect's activity is compromised), time to heat knock-down and/or recovery after chill-coma Alford et al, 2016). CTLs are considered more ecologically relevant as temperature can be raised or cooled using rates that mimic field conditions (Rezende et al, 2011;Alford et al, 2016;Verberk et al, 2016).…”

The impact of climate change on wheat insect pests: current knowledge and future trends

“…Improvements in the tools and techniques currently available will be required (e.g. Pearson and Dawson, 2003;Elith et al, 2006;Alford et al, 2016), along with a re-framing of the climate change research questions we assess (i.e. from what is the impact to how can we manage for a range of responses).…”

Heat shock sensitivity of adult male fertility in the parasitoid wasp Anisopteromalus calandrae (Hymenoptera, Pteromalidae)

“…Compared to lethal consequences, the non-lethal effects of heat stress have received less attention. Sublethal tests include determining critical thermal limits (stress temperature and exposure duration) and time to recovery after chill-coma (Andersen et al, 2015;Alford et al, 2016). From an ecological point of view, sublethal tests are considered more relevant than mortality because the temperature variations used are closer to field conditions (Alford et al, 2016;Verberk et al, 2016).…”