The effects of climate warming on the migratory status of early summer populations of Mythimna separata (Walker) moths: A case-study of enhanced corn damage in central-northern China, 1980-2016.

Mythimna separata (Walker) moths captured in light traps were monitored in Luohe, central-northern China, from 1980 to 2016. Annual average temperature recorded an increase of 0.298°C/10 years in this region in the period. Our results indicate that a rising April and May average temperature and earlier occurrences of days recording the highest day temperature (30°C) caused an advanced peak and increasing proportion of high ovarian development levels of first-generation females in earlier summers. Results using Johnson's formulation of "oogenesis-flight syndrome" indicate that increasing sexual maturity proportion has resulted in more emigrant individuals in the local first-generation moth becoming residents, and then increased individuals rapidly in the local second-generation moth since 2006. Consequences of this action have a boom in corn damage since 2007 in this region. Advanced peak dates of the first and second-generation moth revealed the same response to increasing average monthly temperatures in the monitoring period. Increasing temperatures, the average May temperature exceeds or equal to 22°C, during the early 2000's may represent a physiological threshold for M. separata development. Our results suggest that climate warming may impact M. separata migratory status and cause a problem of crop production in this region.