Too dry or too wet soils have a negative impact on larval pupation of fall armyworm

Abstract

AbstractSoil moisture has an important effect on lepidopteran species, considering larval pupation in soil. The major pest of maize, fall armyworm (FAW) Spodoptera frugiperda (J. E. Smith; Lepidoptera: Noctuidae), is an invasive pest rapidly spreading across the world and has recently invaded China. Similar to other lepidopteran species, the FAW pupation commonly occurs in soils to protect itself against adverse external environments. To study effects of soil moisture on FAW pupation, five soil moisture levels (0%, 25%, 50%, 75% and 100%) were selected. The treatment of 100% soil moisture was excluded since FAW larvae cannot burrow and pupate in such saturated soils. We found that 1) FAW larvae spent more time building pupal chambers at 0% and 75% soil moisture contents than those at 25% and 50%, and chambers at 0% and 75% soil moisture contents had shallower depth; 2). Pupal development times at 0% and 75% soil moisture contents were longer, and 3). FAW larvae at 0% and 75% soil moisture levels had lower percentages of burrowing and pupation. Our study indicates that too dry (0%) or too wet (75%) soils have significantly negative impacts on the larval pupation of FAW. The analysis of FAW responses to soil moisture provides a valuable supplement to pupation ecology about responses of lepidopteran insects to soil moisture. In practice, understanding soil moisture in the cultivation of maize contributes to practical applications of integrated pest management (IPM) strategies in controlling FAW.