Development of Spodoptera exigua Population: Does the Nutritional Status Matter?

SIMPLE SUMMARY: Spodoptera exigua (Hübner) is a common agricultural pest that can harm hundreds of crops. Carbohydrates and proteins are the two key nutrients affecting the development of insect populations. To study the development of the S. exigua population under different carbohydrate and protein nutrition conditions, we constructed a life table of S. exigua under different nutrient conditions: high nitrogen, medium nitrogen–medium sugar, and high sugar. The results showed that there was no significant difference in net reproductive rate among the three nutritional conditions. S. exigua on medium nitrogen–medium sugar diets had the shortest generation time and significantly higher intrinsic rate of increase, finite rate of increase, fecundity, and predicted population at 100 days. These results suggested that an appropriate protein:carbohydrate ratio was beneficial to the rapid development of Spodoptera exigua on farmland. These findings are important for scientifically predicting the population dynamics of S. exigua and constructing a system for controlling the insect population. ABSTRACT: Spodoptera exigua (Hübner) is a common agricultural pest that can harm hundreds of crops. Nutrition conditions can significantly affect the development of insects, especially carbohydrates (C) and proteins (P), which are the two most critical nutrients. To study the development of the S. exigua population under different carbohydrate and protein nutrition conditions, we constructed a life table of both sexes of an S. exigua population under three artificial diets: high nitrogen (P:C = 7:1), medium nitrogen, medium sugar (P:C = 1:1), and high sugar (P:C = 1:7). The results showed that the generation time of S. exigua was 26.38 ± 0.54 d under the medium nitrogen–medium sugar diet, which was the shortest among the three nutrition conditions. The intrinsic rate of increase (0.18 ± 0.01), finite rate of increase (1.20 ± 0.01), fecundity (605.42 ± 36.33 eggs/female), and predicted population at 100 days (8,840,000) were significantly higher under the medium nitrogen–medium sugar condition. There was no significant difference in the net reproductive rate among the three conditions. These results suggested that an appropriate protein:carbohydrate ratio is beneficial to the rapid development of S. exigua on farmland. These findings are important for scientifically predicting the population dynamics of S. exigua from the perspective of nutritional ecology, understanding its catastrophic mechanism, and constructing a prevention and control system.