Effects of acclimation on the thermal tolerance of the brown planthopper Nilaparvata lugens ( S tål)

The influence of acclimation on the cold and heat tolerance of Nilaparvata lugens was determined by measurements of the critical thermal minimum and maximum ( CT min and CT max ), chill and heat coma temperature ( CCT and HCT ) and lower and upper lethal temperature ( LLT 50 and ULT 50 ). First‐instar nymphs were acclimated for 5 days at 15 °C and for 2 days at 30 °C and compared with a population maintained at 23 °C; for the adult comparisons, first‐instar nymphs were reared at 15, 23 and 30 °C until adult emergence, requiring development periods of 50–55, 30–35 and 18–20 days, respectively. The thermal tolerance limits of both age groups changed significantly with acclimation and were correlated with rearing temperature. Across the 48 separate measurements of thermal tolerance ( CT min , CCT , CT max , HCT , LLT 50 and ULT 50 of nymphs and adult males and females), the temperature differential across the three indices of cold tolerance after acclimation at 15 °C compared with a population maintained at 23 °C were between 0.5–2.8 and 2.9–5.0 °C for nymphs and adults, respectively. By comparison, acclimation at 30 °C increased heat tolerance in terms of changes in the CT max , HCT and ULT 50 , and the temperature differentials compared with the 23 °C population were between 1.1–3.3 °C for nymphs and 0.3–1.6 °C for adults. These data indicate that, under the acclimation regimes applied to N. lugens , increases in cold tolerance were greater than heat tolerance.