Effects of Saturated Soil Moisture on Pupal Development Regarding Fall Armyworm

Spodoptera frugiperda, known as fall armyworm (FAW) which is a major pest of corn, is rapidly spreading all over the world as an invasive pest. Similar to other Lepidoptera insects, the FAW pupae usually develop in soil. Therefore, the soil moisture would be an important factor that impacts their growth. In order to study the development and emergence of FAW pupae under 100% soil moisture environment, three factors were selected for experiments in this study: duration of saturated (100%) moisture treatment (0h, 24h, 48h, 72h), initial soil moisture before larvae entering soil (0, 50%), and pupal ages (1-day, 4-day, 7-day). We have discovered that: 1) The emergence percentage of FAW pupae will decrease with the increase of saturated soil moisture treatment time, and the emergence percentage will drop to 0 after 72 hours of continuous treatment. 2) The younger the pupae age of FAW, the more susceptible it would be affected by saturated soil moisture treatment, and the emergence percentage of 7-day-old pupae is higher than the 1-day-old pupae. 3) FAW pupae with entering soil moisture of 0 have a higher survival rate under 100% soil moisture stress, and their emergence percentage is higher than the pupae entered in wet soil (moisture 50%).