Rhythms of pheromone titer in 2 sugarcane pest species <i>Chilo sacchariphagus</i> and <i>Chilo infuscatellus</i> (Lepidoptera: Crambidae)

Chilo sacchariphagus Bojer and Chilo infuscatellus Snellen are 2 major sugarcane pests in southern China. Both species are nocturnal moths that exhibit sexual activity during the night. However, the rhythms of their sexual activities remain poorly documented. In this study, we investigated the sex pheromone titers of both species to determine the effect of age on pheromone production and to characterize the rhythms of pheromone production during the scotophase, when the highest levels are expected to occur. Gas chromatography-mass spectrometry analysis of hexane extracts from female pheromone glands revealed that the titers of 3 sex pheromone components, (Z)-11-hexadecenyl acetate (Z11-16: Ac), (Z)-13-octadecenyl acetate (Z13-18: Ac), and (Z)-13-octadecen-1-ol (Z13-18: OH) were very low on the first night after eclosion, peaked on the second night, and then decreased with age, becoming nearly undetectable by the fourth night in C. sacchariphagus. A similar trend was observed in C. infuscatellus, in which the titer of (Z)-11-hexadecenol (Z11-16: OH) also peaked on the second scotophase. During the second scotophase, the titers of the 3 sex pheromone components in C. sacchariphagus increased rapidly over time from 21:00 to 05:00, peaking between 03:00 and 05:00, and then declined sharply. In contrast, the pheromone titer in C. infuscatellus remained stable during the first 4 h of the scotophase, then rose sharply between 01:00 and 03:00 before declining. These findings contribute to a better understanding of the sexual behavior of these 2 moths and provide a theoretical basis for precise monitoring strategies in the field.