Predicting the realised host-range of Leptinotarsa texana with open-field experiments

Authors: LAFOE, GREG - Agribio, Centre For Agribioscience; Goolsby, John; RACELIS, ALEXIS - University Of Texas Rio Grande Valley; BUTLER, KYM - Agriculture Victoria; RUMPFF, LIBBY - University Of Melbourne; HAUSER, CINDY - Arthur Rylah Institute

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2023
Publication Date: 7/2/2023
Citation: Lafoe, G., Goolsby, J., Racelis, A., Butler, K., Rumpff, L., Hauser, C.E. 2023. Predicting the realised host-range of Leptinotarsa texana with open-field experiments. Biocontrol Science and Technology. https://doi.org/10.1080/09583157.2023.2229970.
DOI: https://doi.org/10.1080/09583157.2023.2229970

Interpretive Summary: Biological control of weeds is a science that involves the importation of specialist plant feeding insects from the native range to control the target weed where it is invasive. In this case, silverleaf nightshade is native to Texas, USA and invasive in Victoria, Australia. One of the key specialist insects that controls silverleaf nightshade in Texas, is the nightshade leaf beetle, Leptinotarsa texana. This candidate biological control agent was exported from Texas to Victoria in the 2010s for evaluation to determine if it would feed only on silverleaf nightshade and not any other closely related crops or native Australian plants. Researchers in Australia documented feeding on eggplant a crop species closely related to silverleaf nightshade. Because eggplant is an important horticultural crop in Victoria, more research was needed in the native range of L. texana where it occurs near plantings of eggplant. Field tests in Weslaco, TX showed that damage to eggplant only occurred when adjacent to sliverleaf nightshade plants which were totally defoliated by the L. texana beetle. Australian regulatory authorities recommended release of the biological control insect to control silverleaf nightshade.

Technical Abstract: The leaf beetle Leptinotarsa texana is a potential biological control for silverleaf nightshade Solanum elaeagnifolium in Australia. However, previous research has shown that L. texana can develop on the non-target crop eggplant Solanum melongena in quarantine cage experiments. We used open-field experiments in the agent’s native range of Texas, USA, to clarify the realised host-range of L. texana in relation to S. melongena. We conducted set design and interspersion experiments to investigate: (1) whether L. texana would show a preference for oviposition when presented with both S. elaeagnifolium and S. melongena in an open-field context, and (2) if larvae would move from defoliated S. elaeagnifolium onto either nearby S. melongena plants, or bypass S. melongena in search of S. elaeagnifolium. Furthermore, we considered how to communicate the contribution of these experiments to the risk analysis for L. texana in a way that could be easily understood by stakeholders and decision-makers. We found evidence that L. texana larvae could cause spill-over damage to S. melongena in situations where co-occurring S. elaeagnifolium is defoliated, but the results from this study do not demonstrate that S. melongena is within the realised host-range of L. texana adults. We demonstrated how an argument map could be used to visually represent the contributions of multiple, sometimes inconclusive, field and laboratory experiments to biological control agent risk analysis.