Abstract: 【Aim】 Male adults of both Frankliniella occidentalis and F. intonsa can release aggregation pheromones, which have two major compounds (R)-lavandulyl acetate and neryl (S)-2-methylbutanoate but in different ratios, and attract both female and male adults. Given the overlap in pheromone components and similar niches between the two species, we hypothesize that aggregation pheromones might play a role in interspecific interactions between the two species.【Methods】 The optimal blends of the two major components for trapping F. occidentalis and F. intonsa female adults in fields were determined by field trapping experiments. In addition, cage experiments were conducted to determine the role of aggregation pheromones in the interspecific interaction between the two closely related thrips species. 【Results】 The results showed that the optimal blend for trapping F. occidentalis adults was 1 250 ng (R)-lavandulyl acetate and 10 000 ng neryl (S)-2-methylbutanoate, while that for trapping F. intonsa adults was 1 250 ng (R)-lavandulyl acetate and 5 000 ng neryl (S)-2-methylbutanoate. In addition, the synthetic aggregation pheromone blend of F. occidentalis determined above had no significant trapping effects on F. intonsa adults and vice versa, suggesting that the aggregation pheromones of the two closely related species are species specific. 【Conclusion】 This study confirmed that species-specificity in aggregation pheromones in the two closely related thrips species is regulated by the ratio of the two major compounds. Meanwhile, the species-specificity might contribute to the pre-mating isolation and reduction of competition between F. occidentalis and F. intonsa. These results provide a theoretical guidance for further understanding the physiological and molecular mechanisms of chemical divergence in the two thrips species, and also a guide for population monitoring and pest control of thrips using aggregation pheromones.

Key words: Frankliniella occidentalis, Frankliniella intonsa, aggregation pheromone, dose, ratio, interspecific interaction