Ecologically relevant measures of the physiological tolerance of light brown apple moth, Epiphyas postvittana, to high temperature extremes

Global warming means that the ability to withstand heat stress is of crucial importance to insects' survival and reproduction. Insects have various ways of achieving thermal tolerance, which can be affected by thermal history, physiological state, and seasonal cycles. In this study, we compared the thermal tolerance of life stages and seasons of a wild population of the striped stem borer, Chilo suppressalis (Walker) (Lepidoptera: Pyralidae), an economically significant pest of rice crops in Asia. Our results demonstrate that the eggs, larvae, and adults of C. suppressalis collected in rice fields in Yangzhou, China, are able to tolerate extremely high temperatures, in excess of those this species encounters in nature. We found that egg masses had a survival rate of 75% after being kept at 42 °C for 8 h. Egg masses exposed to 39 °C for 8 h had the longest hatching time (3.3 days). LTemp50 and LTemp90 (i.e., the temperatures at which 50 or 90% of individuals died within 2 h) of larvae collected in late summer were 45.4 and 47.3 °C, respectively. LTime50 and LTime90 (i.e., the time required to kill 50 or 90% of individuals) at 44 °C were 6.2 and 9.6 h, respectively. The corresponding values for 46 °C were 1.5 and 2.6 h. We also found that the heat tolerance of adults collected in late summer was lower than that of larvae. For example, LTemp50 of male and female adults was 43.8 and 43.6 °C, respectively. Other measures of the heat tolerance of adults, such as LTime50 at 42 °C, also differed between the sexes, being 5.9 h for males and 7.2 h for females. Although adult survival was robust to heat stress, adult fertility was more sensitive. Our results also indicate that although the second generation of adults (i.e., the summer generation) typically encountered higher temperatures than the overwintering generation, survival of the second generation adults was lower.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Heat tolerance of developmental and seasonal stages of Chilo suppressalis

Cao

Liu

et al. 2014

“…Similarly, the survival rates of egg, nymph, and adult of Corythucha ciliata (Say) were relatively high when exposed for 8 h to 35–39 °C and decreased dramatically with the increase of exposure duration at temperatures ≥41 °C (Ju et al., ). Epiphyas postvittana (Walker) was resistant at 32.3–38 °C and susceptible at 40.4 °C in all development stages (Bürgi & Mills, ). Cydia pomonella (L.) adults were tolerant to exposure for 2 h to 41–43 °C (Chidawanyika & Terblanche, ).…”

Section: Discussionmentioning

confidence: 99%

“…The dynamic method, on the contrary, involves exposing invertebrates to ramped temperatures at different rates (Terblanche et al., ). Though the dynamic method was considered to be more ecologically relevant, the static method was still adopted frequently (Ju et al., ; Terblanche et al., ; Bürgi & Mills, ).…”

Section: Introductionmentioning

confidence: 99%

Effects of heat shock on survival and predation of an important whitefly predator,Serangium japonicum

Yao

Zheng

Ding

et al. 2019

Climate change is expected to increase the frequency of periods of extreme weather events, including heat waves that are harmful to arthropod natural enemies. We studied the thermotolerance of the ladybeetle Serangium japonicum Chapin (Coleoptera: Coccinellidae), an important native predator of the whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) in China. Serangium japonicum eggs, first‐ and fourth‐instar larvae, pupae, and adults were subjected to a range of high temperatures (36, 39, 42, 43.5, and 45 °C) at intervals between 15 and 720 min. Survival was compromised and declined sharply for all life stages at temperatures of 42 °C and higher. First instars were the least heat tolerant, and eggs were typically the most resistant. Egg predation by S. japonicum did not differ whether the adult beetles were subjected to either heat shock or starvation first. Heat shock treatments at 36 °C did not impede adult egg consumption, treatments at 39 °C crippled ladybeetle's egg consumption for 8 h following treatment but recovered predatory capacity within 24 h after treatment. However, treatments at 42 °C greatly impaired ladybeetle's predatory capacity. After experiencing heat shock at 39 and 42 °C, adults significantly increased the amount of time they spent resting, which is the probable cause of predation decline after heat exposure. These results demonstrate that short periods of extreme heat exposures have a detrimental impact on S. japonicum survival and predation, but the effect was dependent on duration and life stage. Overall, these findings can help predict population dynamics and success of biological control of whitefly by S. japonicum in a warming world.

“…Indices of thermal tolerance commonly employed to study the thermal tolerance of ectotherms can be categorised as either lethal or sub‐lethal traits. Lethal traits, resulting in the death of the organism, include lethal temperature (Terblanche et al., ), lethal time (Bürgi & Mills, ), and supercooling point (Formby et al., ). Sub‐lethal traits include critical thermal temperatures (Klok & Chown, ), coma temperatures (Alford et al., ; Everatt et al., ), and coma recovery times (Andersen et al., , ); these are traits measured prior to the point of temperature‐induced mortality.…”

Section: Introductionmentioning

confidence: 99%

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

Alford

Burel

Baaren

2016

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