Effect of host plants on life-history traits of Spodoptera exigua (Lepidoptera: Noctuidae)

Host plants play an important role in population increases and outbreaks of cosmopolitan polyphagous insect pest, such as Spodoptera exigua (Hubner; Lepidoptera: Noctuidae). We investigated the impact of various host plants (cauliflower, peas, and wheat) on fitness and relative growth rate of S. exigua and intrinsic rate of population increase. The S. exigua population was collected from cauliflower fields from Multan, Pakistan. Comparison of various life-history traits on three different host plants revealed significant differences that might be correlated with the fitness costs. The mean number of eggs laid by female reared on cauliflower was significantly greater than on peas or wheat. Similarly, eggs viability, intrinsic rate of population increase, adult eclosion, and adult's longevity were significantly higher on cauliflower than on peas and wheat. The low survival on peas and wheat suggest the unsuitability of these host plants, while the higher pupal weight on cauliflower suggest that it provides better food quality to S. exigua compared with peas and wheat. On peas and wheat, fitness declined with each generation suggesting that the average fitness of individuals may decline due to the elimination of insects with higher fitness. Our results suggest that cauliflower was the most nutritive and preferred host plant. Such results could be useful to design cultural management strategies, which may include trap cropping.