Interactive Effects of Temperature and Plant Host on the Development Parameters of Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae)

Simple Summary The beet armyworm Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae) is an economic pest that causes significant damage to various vegetables and field crops in Korea. Timely forecasting of pest emergence and occurrence plays a vital role in pest management. To predict the spring emergence and population dynamics of S. exigua, constant temperature-mediated developmental parameters of S. exigua were studied with linear and nonlinear models on different plant hosts. The temperature and plant host significantly influenced the development of S. exigua. The total developmental time decreased with the increase in temperature, although there was no development at extreme temperatures. We developed a forecasting model, and our findings predicted the spring emergence of S. exigua in June. Thus, continuous monitoring of S. exigua in crop fields is needed to be ready to take advanced management measures against S. exigua. This study investigated the effects of different temperatures (15, 20, 25, 27, 30, 35, and 40 degrees C) on the development rate of Spodoptera exigua (Hubner) eggs, larvae, pupae, and total immatures on plant hosts (soybean, maize, potato, and green pea). The eggs of S. exigua developed successfully at all the tested temperatures, except at 40 degrees C. The total developmental time (egg-adult) decreased with an increasing temperature from 15 to 35 degrees C on plant hosts. Stage-specific parameters such as the lower threshold temperature (TH) were determined using linear and nonlinear models (Sharpe-Schoolfield-Ikemoto [SSI]). The lower developmental threshold (LDT) and thermal constant (K) were determined using a linear model. The LDT and K for the total immature stage had respective values of 11.9 degrees C and 397.27 degrees -day (DD) on soybean, 11.6 degrees C and 458.34 degrees -day (DD) on maize, 11.2 degrees C and 446.23 degrees -day (DD) on potato, 10.7 degrees C and 439.75 degrees -day (DD) on green pea, and 12.2 degrees C and 355.82 degrees -day (DD) on the artificial diet. The emergence frequency of adult S. exigua over the full range of constant temperatures was simulated using nonlinear developmental rate functions and the Weibull function. This study predicted the spring emergence date in the first to second weeks of June, with approximately five generations for plant hosts. The interaction of temperature and plant host also influenced the development and longevity of the adults. Overall, the findings of this study may be useful for predicting the number of generations, occurrence, population dynamics in crop fields, and management of S. exigua.