Influence of temperature on the northern distribution limits of Scirpophaga incertulas Walker (Lepidoptera: Pyralidae) in China

We explored the influence of temperature on the northern distribution limits of Scirpophaga incertulas Walker, an important agricultural pest of rice in Asia. We analyzed ≥48 years of records from 186 climate stations of Mainland China to estimate the annual probabilities of reaching the lower lethal temperature for S. incertulas. The relevant climatic metric, minimum annual temperature, approximated a normal distribution. Consequently, the probability density function for any site could be characterized with the mean and standard deviation of minimum annual temperatures. We used the local regression method to map the mean and standard deviation of minimum annual temperatures throughout Mainland China and then calculated isolines representing annual probabilities for reaching or exceeding the lower lethal temperature of S. incertulas. In addition, we calculated and mapped the number of generations per year based on the annual accumulative degree days and the sum of effective temperatures required to complete one generation. The empirical northern distribution limits of S. incertulas were generally congruent with the theoretical limits based on winter survival, with exceptions within the Shandong and Sichuan provinces, which are apparently thermally suitable but where the host plant is not cultivated. The expected number of generations per year was 3–5 within most of the range of S. incertulas in China. In central China, the expected number of generations per year was about 3. A climate warming scenario of 4 °C in minimum and maximum daily temperatures predicted an increase in the expected number of generations per year in central China from about 3 to 4.

Graphical AbstractFigure optionsDownload as PowerPoint slideHighlights
► Minimum annual temperatures determine the distribution limits of S. incertulas.
► Annual accumulated effective temperatures determine the voltinism of S. incertulas.
► Global warming will affect the expected voltinism of S. incertulas in Central China.