Biological Control of Blue Heliotrope A report for the Rural Industries Research and Development Corporation by David Briese and Miguel Zapater September 2001 RIRDC Publication No 01/119 RIRDC Project No CSE-82A © 2000 Rural Industries Research and Development Corporation. All rights reserved. ISBN 0 642 58341 2 ISSN 1440-6845 Biological Control of Blue Heliotrope Publication No. 01/119 Project No. CSE-82A The views expressed and the conclusions reached in this publication are those of the author and not necessarily those of persons consulted. RIRDC shall not be responsible in any way whatsoever to any person who relies in whole or in part on the contents of this report. This publication is copyright. However, RIRDC encourages wide dissemination of its research, providing the Corporation is clearly acknowledged. For any other enquiries concerning reproduction, contact the Publications Manager on phone 02 6272 3186. Researcher Contact Details David Briese Miguel Zapater GPO Box 1700 Facultad de Agronomía Canberra ACT 2601 Universidad de Buenos Aires Phone: 02 6246 4045 Av. San Martín, 4453 Fax: 02 6246 4000 1417 Buenos Aires, Argentina Email: [email protected] Email: [email protected] RIRDC Contact Details Rural Industries Research and Development Corporation Level 1, AMA House 42 Macquarie Street BARTON ACT 2600 PO Box 4776 KINGSTON ACT 2604 Phone: 02 6272 4539 Fax: 02 6272 5877 Email: [email protected]. Website: http://www.rirdc.gov.au Published in August 2001 Printed on environmentally friendly paper by Canprint ii Foreword Blue heliotrope, Heliotropium amplexicaule Vahl, is a perennial, spreading broad-leaf weed of temperate South American origin. It was introduced into Australia in the late 19th century as a garden ornamental and now occurs in four states. In northern New South Wales and southern Queensland it has undergone rapid recent spread in cultivated pastures. It is considered a serious weed in these areas because it competes with desirable summer pasture species and is toxic to stock. Conventional methods, including herbicide use have had limited success in reducing its impact and have not stopped its spread. Moreover, recent concerns raised over contamination of livestock and livestock produce by the build up of residual chemicals in the soil, emphasise the need for non-chemical, non-polluting methods of weed control. Biological control would provide such an option and enhance Australia’s reputation for exporting clean livestock produce. This publication describes investigations in South America aimed at identifying natural enemies of blue heliotrope in its native range and determining their potential for biological control of the weed in Australia. One agent, the leaf-beetle, Deuterocampta quadrijuga, was selected for introduction and the report describes the formal quarantine testing, leading to an application for release of the beetle in the field. Finally, recommendations are made on future work needed to achieve effective biological control. This project was funded from RIRDC Core Funds, which are provided by the Federal Government, in order to ensure the successful initiation of the project. This report, a new addition to RIRDC’s diverse range of over 700 research publications, forms part of our Resilient Agricultural Systems R&D program, which aims to foster agri-industry systems that have sufficient diversity, flexibility and robustness to be resilient and respond to challenges and opportunities. Most of our publications are available for viewing, downloading or purchasing online through our website: downloads at www.rirdc.gov.au/reports/Index.htm purchases at www.rirdc.gov.au/eshop Peter Core Managing Director Rural Industries Research and Development Corporation iii Acknowledgments This project would not have been possible without the efforts of the Blue Heliotrope Action Committee, a coalition of landholders, Landcare coordinators, State and local government representatives formed in 1996 to promote the better management of this weed. Their belief that biological control could provide a solution to the problems of blue heliotrope and their tireless lobbying of government and research agencies for support was critical to the funding of the project. Without detracting from the efforts of all members of this group, special thanks are due to Bill Lambell and Jen Finlayson for their ongoing help and interest with this project. Thanks are also due to Bill Pettit, Gerardo Serra, and Gladys Perez-Camargo for their contributions to the research in Argentina. Andrea Andorno undertook studies on the host-range of insects as part of an Agricultural Science thesis at the University of Buenos Aires. Penny Reynolds carried out the initial part of the blue heliotrope ecology studies in Australia as part of an Agricultural Science degree at Sydney University. Plants for formal host-specificity testing were supplied by: Laurie Adams, Australian National Herbarium, Canberra, ACT; Robin Coles, Adelaide, SA; Penny Edwards, CSIRO, Darwin, NT; Graeme Errington, Mt Annan Botanic Gardens, NSW; Peter Horsfall, Sturt Desert Park, NT; Tanya McAndrew and Michael Day, Queensland Department of Natural Resources and Mining, Sherwood, QLD; Chris O’Donnell, Department of Primary Industries, Gayndah, QLD; and Garry Sankowsky, Yuruga Nursery, Atherton, QLD. Andi Walker carried out the host-specificity tests in the CSIRO Black Mountain Quarantine Facility. iv Contents Foreword iii Acknowledgments iv Executive Summary vi 1. Introduction 1.1 Background 1 1.2 Project Aims 2 2. Studies in Argentina 2.1 Blue Heliotrope Surveys 3 2.2 Preliminary Host-Specificity Testing 6 2.3 Impact of Candidate Agents 9 2.3.1 Deuterocampta quadrijuga 9 2.3.2 Longitarsus sp. 10 3. Studies in Australia 11 3.1 Ecology of Blue Heliotrope 11 3.2 Quarantine Testing of Deuterocampta quadrijuga 12 4. Discussion 16 4.1 Strategy for the biological control of blue heliotrope 16 4.2 Implications 16 5. Recommendations 17 6. References 18 v Executive Summary Blue heliotrope, Heliotropium amplexicaule Vahl, is a perennial, spreading broad-leaf weed of temperate South American origin. It was introduced into Australia in the late 19th century as a garden ornamental and now occurs in four states. In northern NSW South Wales and southern Queensland it has undergone rapid recent spread in both cultivated pastures and crops. It is considered a serious weed in these areas because it competes with desirable summer pasture species and is toxic to stock. Herbicides have had limited success in reducing its impact and have not stopped its spread. Biological control offers an important control option that could reverse the current low success in management of this weed. A research base was set up in Argentina, and a local entomologist contracted for the project. Three surveys conducted throughout the range of blue heliotrope in Argentina identified four insect species as having potential for biological control: the leaf feeding beetle, Deuterocampta quadrijuga; the flea-beetle, Longitarsus sp., which feeds on leaves as an adult and on roots as a larva; the bug, Dictyla sp., which sucks sap from the cells of leaves, killing them; and the thrips, Haplothrips heliotropica, whose feeding causes deformation of leaves and buds. In addition, a pathogen, the leaf- blotch fungus Pseudocercosporella sp., was found to cause die-back of infected blue heliotrope plants. An open-field host-specificity trial was carried out to make a preliminary assessment of the host-range of the four insect species. It showed that all four insects were restricted to the genus Heliotropium, with evidence of strong preferences for a limited number of species within that genus. The field surveys had indicated that the leaf-beetle, D. quadrijuga, and the flea-beetle, Longitarsus sp., were the most damaging agents. Field experiments were set up to study the biology and impact of these two species, and showed that both were capable of completely defoliating blue heliotrope plants. The leaf-beetle caused relatively rapid defoliation by mid-summer under natural conditions, while the flea-beetle had a slower impact, causing a gradual decline in plant size and death of most plants by autumn. The leaf-beetle was selected for the first introduction into Australia. Testing at the Black Mountain Quarantine Facility, Canberra, showed that it was restricted to South American sections of the genus Heliotropium as host-plants and did not pose a risk to non-target plant species, including native Australian Heliotropium species. Based on these results, Australian plant biosecurity authorities approved the release of D. quadrijuga for the biological control of blue heliotrope in July 2001. The work of this project will lead to the field release of the leaf-beetle, for biological control of blue heliotrope in Australia. The first such release is planned for October 2001. The project enabled the development of a biocontrol strategy, which suggests that control would be more effective if additional agents, such as a root-feeding insect or pathogen, could complement the actions of the leaf-beetle. Such agents have been identified in the current project, but further work is needed to determine if they are safe for release. Successful biological control would lead to a significant reduction in the economic and environmental impact of this toxic noxious weed through environmentally-benign and self-sustaining means. It would also provide an additional tool for the integrated management of the weed. However, to fully realise