Optimizing sex pheromone lures for male trapping specificity between Spodoptera frugiperda and Mythimna loreyi

BACKGROUND: Spodoptera frugiperda and Mythimna loreyi are sympatric pests of corn and other gramineous crops. In addition, the two species share three primary pheromone components Z9-14:Ac, Z7-12:Ac and Z11-16:Ac, resulting in capture of males from both species by commercially available lures, which poses a great challenge for species-specific population monitoring. RESULTS: To increase the specificity of the pheromone blend used in lures, we conducted comparative investigations between the two species, with respect of female calling rhythms, components in female pheromone glands, male electrophysiological and sexual excitement responses to pheromone gland components. Based on differences between the two species obtained from these investigations, we further designed and tested a variety of blend formulations for the species-specificity in the field trapping assays, with the reported ternary blend for S. frugiperda (Z9-14:Ac/Z7-12:Ac/Z11-16:Ac = 88/1.0/11) as a positive control. The results showed that the ratio of component Z7-12:Ac is the major determinant of the male trapping specificity of the blends in lures. Compared to the positive control, increasing the ratio of Z7-12:Ac to 10 in the ternary blend greatly improved the specificity and captures for M. loreyi males, while reducing its ratio to 0.4 significantly improved the specificity and retained the capture ability for S. frugiperda males. CONCLUSION: The optimal blend was determined to be Z9-14:Ac/Z7-12:Ac/Z11-16:Ac at a ratio of 88/0.4/11 for S. frugiperda, and 88/10/11 for M. loreyi. These findings offer highly species-specific sex pheromone formulations for population monitoring and male trapping of the two sympatric pests. © 2025 Society of Chemical Industry.