Effect of a near-zero magnetic field on development and flight of oriental armyworm (Mythimna separata)

Authors: YAN, MENG-MENG - Chinese Academy Of Agricultural Sciences; ZHANG, LEI - Chinese Academy Of Agricultural Sciences; CHENG, YUN-XIA - Chinese Academy Of Agricultural Sciences; Sappington, Thomas; PAN, WEI-DONG - Chinese Academy Of Sciences; JIANG, XING-FU - Chinese Academy Of Agricultural Sciences

Submitted to: Journal of Integrative Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/2/2020
Publication Date: 4/13/2021
Citation: Yan, M., Zhang, L., Cheng, Y., Sappington, T.W., Pan, W., Jiang, X. 2021. Effect of a near-zero magnetic field on development and flight of oriental armyworm (Mythimna separata). Journal of Integrative Agriculture. 20(5):1336-1345. https://doi.org/10.1016/S2095-3119(20)63287-7.
DOI: https://doi.org/10.1016/S2095-3119(20)63287-7

Interpretive Summary: The oriental armyworm, Mythimna separata, is one of the most important pests of corn in Asia. Like many closely-related pests of corn in the U.S., including the sister armyworm species Mythimna unipuncta, it overwinters in the south and migrates long distances to northern regions in the spring and summer. After arrival, the migrant adults lay eggs in corn and other crops, after which larvae hatch and damage the plants. Many migratory insects use the earth's magnetic field to navigate, and the magnetic field can affect other behaviors and development as well. Identifying the effects can be determined experimentally by artificially "removing" the earth's magnetic field by countering it with magnetic coils in the laboratory, then looking at the effects on the insects. In this study, rearing larvae under a near-zero magnetic field had negative effects on development and flight behavior. Because the earth's magnetic field is weaker in southern regions where M. separata overwinters compared to northern regions where it invades every spring and summer, the results suggest that differences in magnetic field strength may influence this pest's migratory behavior and outbreak potential in different ways depending on latitude. These results will be of interest to government and university scientists studying the behavior and population dynamics of this and other migratory insect pests.

Technical Abstract: The geomagnetic field, a basic physical element of nature, affects all living organisms on Earth. In this study we investigated the developmental and behavioral effects of rearing M. separata in a near-zero magnetic field (<500 nT) compared to the local geomagnetic field (approximately 50µT). A near-zero magnetic field was produced by a Helmholtz coil system. Elimination of the geomagnetic field significantly lengthened M. separata larval and pupal development durations, increased male longevity, and reduced pupal weight, female reproduction, and the relative expression level of the vitellogenin (Vg) gene in newly emerged females. Moreover, the near-zero magnetic field had a considerable negative effect on the percentage of adults that mated. In addition, adult moths in the near-zero magnetic field displayed less flight activity late in the night than those in the earth’s normal geomagnetic field.