Abstract
The brown planthopper Nilaparvata lugens (Stål) is the most serious pest of rice across the world, especially in tropical climates. N. lugens nymphs and adults were exposed to high temperatures to determine their critical thermal maximum (CTmax), heat coma temperature (HCT) and upper lethal temperature (ULT). Thermal tolerance values differed between developmental stages: nymphs were consistently less heat tolerant than adults. The mean (± SE) CTmax of nymphs and adult females and males were 34.9±0.3, 37.0±0.2 and 37.4±0.2°C respectively, and for the HCT were 37.7±0.3, 43.5±0.4 and 42.0±0.4°C. The ULT50 values (± SE) for nymphs and adults were 41.8±0.1 and 42.5±0.1°C respectively. The results indicate that nymphs of N. lugens are currently living at temperatures close to their upper thermal limits. Climate warming in tropical regions and occasional extreme high temperature events are likely to become important limiting factors affecting the survival and distribution of N. lugens.
Highlights
Temperature has a direct influence on many life history parameters of insects ([1], [2], [3], [4], [5])
The critical thermal maximum (CTmax) was significantly lower in first instar nymphs than adults (ANOVA; F2, 27 = 33.550, p,0.001), but not between the sexes
The heat coma temperature (HCT) of nymphs was significantly lower than the adult morphs (ANOVA; F2, 27 = 68.214, p,0.001), and between the sexes (p = 0.013), with females having the higher HCT
Summary
Temperature has a direct influence on many life history parameters of insects ([1], [2], [3], [4], [5]). Whilst cold tolerance has been an area of research interest since the pioneering studies of Salt ([15], [16]), there has been less focus on the high temperature tolerance of insects, especially those living in tropical areas, or on the proximity of their upper thermal limits to current and future temperature regimes. This may be explained by the assumption that insects already living in high temperature environments may be less affected by increases in temperature than species inhabiting cooler climates, or that they have the ability to cope with such changes [17]. As with many tropical species, there is a lack of information about the high temperature tolerance of N. lugens and the likely effects doi:10.1371/journal.pone.0029409.g001
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