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ARS Home » Southeast Area » Fort Lauderdale, Florida » Invasive Plant Research Laboratory » Research » Publications at this Location » Publication #322546
Title: Larinus minutus (Coleoptera: Curculionidae) and Urophora quadrifasciata (Diptera: Tephritidae), evidence for interaction and impact on spotted knapweed in Arkansas

Author
item Minteer, Carey
item KRING, TIMOTHY - University Of Arkansas
item WIEDENMANN, ROBERT - University Of Arkansas

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2016
Publication Date: 6/1/2016
Citation: Minteer, C., Kring, T.J., Wiedenmann, R.N. 2016. Larinus minutus (Coleoptera: Curculionidae) and Urophora quadrifasciata (Diptera: Tephritidae), evidence for interaction and impact on spotted knapweed in Arkansas. Environmental Entomology. 43:3,658-662.

Interpretive Summary: Competition between seed-feeding insects is well noted in the literature, with many of these interactions being asymmetrical and causing a disadvantage for one of the species involved. While often effective, the use of the “cumulative stress” approach to biological control (where multiple natural enemy species are released to increase control) may increase the risk of competition among natural enemies released, which can lead to less effective biological control programs. Spotted knapweed is an invasive plant that causes damage in rangelands and pastures. In Arkansas, two biological control agents for spotted knapweed, Larinus minutus, the knapweed seedhead weevil and Urophora quadrifasciata, the UV fly are established. Both species attack the seedheads of spotted and diffuse knapweeds. There is potential for interactions between these species and this could affect the efficacy of the biological control program. To evaluate these potential interactions, we collected seedheads of spotted knapweed weekly from three sites in Arkansas from 2010 through 2012. Seedheads were monitored for emergence of L. minutus and U. quadrifasciata and the effect on seed reduction was analyzed. We determined that the occurrences of the weevil and the fly were not independent of each other. The weevil is more effective at reducing spotted knapweed seed production than the fly. Seedheads with both natural enemies present are no different from seedheads with L. minutus. These results indicate that while an interaction between these two natural enemies is occurring, the interaction will likely not have any effects on the overall efficacy of the biological control program.

Technical Abstract: Competition between seed-feeding insects is well noted in the literature, with many of these interactions being asymmetrical and causing a disadvantage for one of the species involved. While often effective, the use of the “cumulative stress” approach to biological control (where multiple natural enemy species are released to increase control) may increase the risk of competition among natural enemies released, which may lead to less effective biological control programs. Spotted knapweed (Centaurea stoebe ssp. micranthos) is an invasive plant that causes damage in rangelands and pastures. In Arkansas, two biological control agents for spotted knapweed, Larinus minutus Gyllenhal and Urophora quadrifasciata Meigen, are established. Both species attack the capitula of spotted and diffuse knapweeds. There is potential for interactions between these species and this could affect the efficacy of the biological control program. To evaluate these potential interactions, we collected spotted knapweed capitula weekly from three sites in Arkansas in 2010 through 2012. Capitula were monitored for emergence of L. minutus and U. quadrifasciata and the effect on seed reduction was analyzed. We determined that the occurrences of L. minutus and U. quadrifasciata were not independent of each other. Larinus minutus is more effective at reducing spotted knapweed seed production than U. quadrifasciata. Capitula with both natural enemies present are no different from capitula with L. minutus. These results indicate that while an interaction between these two natural enemies is occurring, the interaction will likely not have any effects on the overall efficacy of the biological control program.