Abiotic factors influencing Helicoverpa zea pupation

Many soil-dwelling pests are understudied because of difficulties in directly observing their behavior in the soil. Moreover, some species spend only a portion of development in the soil and are well-studied above ground, but not below ground. We observed one such species, Helicoverpa zea (Boddie), in three distinct soil types (Belhaven muck, Mecklenburg loam, and Candor sand) to reassess how environmental factors impact pupation biology of the species below the soil. Past studies indicated soil type may be important, but were not repeatable. During 2020-2021, we conducted a common garden experiment in NC and SC. Each plot consisted of a plastic storage tote filled using collected soil and infested with 20-25 ears of corn containing H. zea larvae. After larvae exited the ear, burrowed into the soil, and molted, pupae were hand-excavated to measure the depth. We observed a significant difference in pupal depth by soil type, as well as an interaction between soil type and region. Pupae were found to dig deepest in Candor sand at both locations (6.4 and 5.1 cm), shallower in Belhaven muck (5.3 and 4.0 cm), and shallowest in Mecklenburg loam (3.1 and 3.0 cm). Additional studies demonstrated a significant interaction between pupal depth and soil moisture indicating the importance of moisture on pre-pupal behavior. Our results demostrate a strong impact of two abiotic factors on H. zea pupal depth. Future studies should investigate the impact of these and other factors on depth, as well as other biological parameters such as survival and emergence.