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ARS Home » Southeast Area » Fort Lauderdale, Florida » Invasive Plant Research Laboratory » Research » Publications at this Location » Publication #332169

Research Project: Identification, Evaluation, and Implementation of Biological Control Agents for Invasive Weeds of Southeastern Ecosystems

Location: Invasive Plant Research Laboratory

Title: Predicting spillover risk to non-target plants pre-release: Bikasha collaris a potential biological control agent of Chinese tallowtree (Triadica sebifera)

Author
item Wheeler, Gregory
item Duncan, James
item Wright, Susan

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2017
Publication Date: 2/17/2017
Citation: Wheeler, G.S., Duncan, J.G., Wright, S.A. 2017. Predicting spillover risk to non-target plants pre-release: Bikasha collaris a potential biological control agent of Chinese tallowtree (Triadica sebifera). Biological Control. 180:16-21.

Interpretive Summary: This research was conducted to answer the question, "What will biological control agents eat after they have eaten all the weed?" Quarantine host range tests accurately predict direct risk of biological control agents to non-target species. However, a well-known indirect effect of biological control of weeds releases is spillover damage to non-target species. Spillover damage may occur when the population of agents achieves outbreak densities, depletes the target weed, and may spillover causing damage to non-target species. Similar to the a-priori assessment of direct risks to non-targets, we assessed the indirect risk of spillover damage to non-targets pre-release. These quarantine experiments were conducted on the flea beetle (Bikasha collaris) a potential biological control agent of Chinese tallowtree, a weed of wetlands, forests, and natural areas in the southeastern U.S.A. By feeding recently emerged, naïve flea beetle adults leaves of Chinese tallowtree, three close relatives that are non-target species, Gulf sebastian bush (Ditrysinia fruticosa), Oysterwood (Gymnanthes lucida), Manchineel (Hippomane mancinella), or water we showed that adult longevity, egg production, and leaf damage were greatest on the weed and near zero or zero on the non-targets. We simulated a spillover event by transferring adults to these non-target species or water after feeding on Chinese tallowtree for 2 or 4 weeks and found similar longevity and egg production as those fed only water. These results indicated pre-release that when tallow-fed adults are forced to feed on these non-target species, risk of spillover is very low. We showed that the Chinese tallowtree biological control agent, the flea beetle will only be able to sustain a population on the target weed.

Technical Abstract: Quarantine host range tests accurately predict direct risk of biological control agents to non-target species. However, a well-known indirect effect of biological control of weeds releases is spillover damage to non-target species. Spillover damage may occur when the population of agents achieves outbreak densities, depletes the target weed, and may spillover causing damage to non-target species. Similar to the a-priori assessment of direct risks to non-targets, we assessed the indirect risk of spillover damage to non-targets pre-release. These quarantine experiments were conducted on the flea beetle Bikasha collaris, a potential biological control agent of Chinese tallowtree, Triadica sebifera, a weed of wetlands, forests, and natural areas in the southeastern U.S.A. By feeding recently emerged, naïve B. collaris adults leaves of Chinese tallowtree, three close relatives that are non-target species, Ditrysinia fruticosa, Gymnanthes lucida, Hippomane mancinella, or water we showed that adult longevity, egg production, and leaf damage were greatest on the weed and near zero or zero on the non-targets. We simulated a spillover event by transferring adults to these non-target species or water after feeding on Chinese tallowtree for 2 or 4 weeks and found similar longevity and egg production as those fed only water. These results indicated pre-release that when tallow-fed adults are forced to feed on these non-target species, risk of spillover is very low. We showed that the Chinese tallowtree biological control agent B. collaris will only be able to sustain a population on the target weed.