Interference competition between Frankliniella occidentalis (Pergande) and Frankliniella intonsa (Trybom): Feeding assay

Frankliniella occidentalis (Pergande) and Frankliniella intonsa (Trybom) (Thysanoptera: Thripidae) are sympatric flower-dwelling thrips infesting various agricultural crops in eastern Asia. Recently, F. intonsa (native) has been found dominant regionally although F. occidentalis (invasive) is generally considered as a major species in Korea. As a hypothesis to explain the variation in occurrence pattern in the fields, we examined the interspecific competition between the two species in laboratory by providing different food sources including honey, pollen, and kidney bean leaf. Five behavioral parameters, i.e., confronting, wandering, resting, food guarding, and feeding were observed. Results showed that adult F. intonsa is better in guarding and feeding on both honey and pollen than F. occidentalis although such a pattern was not found in larval stage. Adult F. intonsa guarded and fed honey 8.5 and 1.5 times longer period of time than F. occidentalis. And, in pollen F. intonsa guarded and fed 32.9 and 1.9 times longer than F. occidentalis. In leaf feeding experiment, area of feeding mark on bean leaf made by both F. intonsa and F. occidentalis (competition condition) was not significantly different from those made by each species (no-competition condition). From these results, interference competition exists between F. occidentalis and F. intonsa, and F. intonsa is a better competitor especially in adult stage. Therefore, we suggest interspecific competition between the two species could be one of the underlying mechanisms for the differential occurrence pattern in the fields.

Keywords: flower thrips · food guarding · feeding · seasonal occurrence · invasive species