A description of temperature-dependent development to infer <i>Hyphantria cunea</i> (Lepidoptera: Erebidae) and its application to predict the species voltinism in China

The fall webworm, Hyphantria cunea (Drury) (Lepidoptera, Erebidae) is a significant forest pest, known for its strong reproductive capacity and wide host range. Temperature plays a crucial role in its growth and development, influencing population dynamics. Global warming may alter its distribution, development timing, and control measures. We selected six temperatures (16 °C, 19 °C, 22 °C, 25 °C, 28 °C, and 31 °C) for rearing H. cunea in artificial climate chambers and recorded the duration of each developmental stage. Seven developmental rate models were used to fit the developmental progression of H. cunea. The results showed that temperature significantly affected the development time of H. cunea, as increasing temperature accelerated development, especially in the range of 16 °C to 28 °C. At 31 °C, the effect of temperature on the rate of development began to lessen. The fitting results based on the Lactin model showed that the lower threshold temperature (TL) of the development of H. cunea was 10 °C; the upper threshold temperature (TH) was 33.01 °C, and the optimal temperature (Topt) was 31.87 °C. The most effective accumulated temperature for completing the life cycle was 791.2 degree days. The calculation of annual accumulated degree days over the past five years showed that H. cunea in China normally has three generations per year, with a few colder regions supporting two generations annually. In exceptionally hot years, there may be a completely fourth generation.