Fitness of Mythimna separata (Lepidoptera: Noctuidae) on Cultivated Wheat and a Weed, Wild Oat (Avena fatua), and Its Implications for Pest Management

<i>Mythimna separata</i> (Walker), a significant migratory pest in many Asian countries, can cause severe damage to wheat crops. Understanding whether wild oat can serve as an alternate host is important for informing predictive models of <i>M. separata</i> infestation levels in wheat fields and can improve pest and weed management strategies. We first conducted both choice and no-choice experiments and found that <i>M. separata</i> readily laid eggs on both wheat and wild oat, with no significant oviposition preference. However, newly hatched larvae exhibited a strong preference for wheat, with 53.34% more larvae feeding on wheat compared to wild oat. Development time from egg to adult emergence was significantly shorter in <i>M. separata</i> fed on wheat than on wild oat, although the durations of the larval and pupal stages varied depending on the host plant. Despite these differences in development time, host plants did not significantly affect larval survival, pupal weight, fecundity, and adult longevity. The mean number of eggs laid by females that fed on wheat and wild oat were 1202.12 and 1270.54 eggs/female, and larval survival rates were 81% and 84%, respectively. Our findings suggest that wild oat can serve as a suitable host for <i>M. separata</i> and may act as a refuge when wheat fields are treated with insecticides. The high larval preference for wheat over wild oat indicates that <i>M. separata</i> on wild oat may easily disperse to wheat, complicating pest control and highlighting the need to include wild oat in pest management strategies.