Effects of Juvenile Hormone Analog and Days after Emergence on the Reproduction of Oriental Armyworm, Mythimna separata (Lepidoptera: Noctuidae) Populations

Abstract

Mythimna separata (Walker) is a main cereal crop pest that causes extensive damage to the world grain production. The effects of juvenile hormone on M. separata populations remain poorly understood. Here, we explored how JH analog (JHA) affected reproductive traits of both migrant and resident populations in this pest. Our results showed that the influence of JHA treatment on reproduction depended on adult age (days after emergence) of exposure to JHA and populations. Exposure of M. separata residents to JHA (methoprene) on day 1 and day 2 after adult emergence significantly shortened the pre-oviposition period, but increased the lifetime fecundity, mating frequency and grade of ovarian development compared to the controls. However, M. separata migrants exposed to JHA only on day 1 facilitated their reproduction, resulting in a reduction in the pre-oviposition period but an increase in lifetime fecundity, mating frequency and grade of ovarian development. In addition, exposure to JHA from day 2 to day 4 did not significantly affect the ovarian and reproductive development in both migrant and resident populations. These results indicated that the first two days after adult emergence were the sensitive period for residents. In contrast, only the first day after adult emergence was the sensitive stage for migrants. Our findings will contribute to a better understanding of JHA function on M. separata populations.

Transcriptomics Provide Insights into the Photoperiodic Regulation of Reproductive Diapause in the Green Lacewing, Chrysoperla nipponensis (Okamoto) (Neuroptera: Chrysopidae)

“…In our recent study, we found that exogenous JH treatment significantly shortened the pre-oviposition period of diapausing C. nipponensis female adults [53]. A similar result has also been observed in the oriental armyworm Mythimna separata and C. septempunctata [54][55][56]. Here, we knocked down the key gene CnJhamt1, involved in juvenile hormone synthesis in diapause-sensitive C. nipponensis during the diapause-sensitive period, and we found that the pre-oviposition period of C. nipponensis was significantly prolonged (Figure 6A), which indicated that the gene has an influence on the reproductive capacity of diapause-sensitive C. nipponensis.…”

Biological Characteristics and Energy Metabolism of Migrating Insects

“…The topical treatment of migratory insects with JH analogs can allow us to observe changes in their flight and reproductive activities and analyze specific regulatory effects. When the JH analog methoprene was applied to the body surface of 1-day-old M. separata , the pre-oviposition period of female moths was shortened, their reproductive ability was significantly increased, and their flight capacity was significantly inhibited [ 21 , 85 ]; in addition, the content of glycerides as flight energy material was significantly decreased [ 86 ]. When M. separata experience starvation or flight at the age of 1 day, the JH titer increases, directly promoting an increase in the oviposition and a shortened pre-oviposition period in adult moths [ 87 ].…”