Variations in Calling Behavior of Fall Armyworm, Spodoptera frugiperda (J. E. Smith) Populations: Influence of Age and Geographical Location

We investigated the female calling rhythm of fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), in populations collected from four Indian states. Observations were made for six days after adult eclosion during scotophase. We measured the onset of calling, calling duration and the proportion of females calling. These traits varied with population, female age and their interaction. Females from the Maharashtra (M) and Karnataka (K) populations initiated calling later after the onset of scotophase than females from the Telangana (T) and Gujarat (G) populations. On the day of emergence, females from all geographical populations initiated calling relatively late; the onset of calling became progressively earlier with age and was earliest on day 6. Females from the G and T populations called for longer periods than those from the M and K populations. Calling duration increased as females aged, reached its maximum on day 5, and declined slightly thereafter. The proportion of females calling between 22:00 hr. and 24:00 hr. increased through day 4, when it was highest, and then decreased. This study provides novel insights into the chemical ecology and reproductive behavior of Spodoptera frugiperda in India. We investigated the geographical variations in sex pheromone composition and female calling behavior, which are important for improving pheromone-based monitoring, mass trapping and mating disruption strategies. Future studies should evaluate more Indian FAW populations, investigate environmental influences on pheromonal communication, and develop optimized pheromone blends for large-scale IPM programs.