Biological Control of Paterson's Curse with the Taproot Flea Beetle
Note Number: LC0155
Published: January 1999
Updated:
Common and scientific names
Paterson’s curse taproot flea beetle
Longitarsus echii Koch
Family Chrysomelidae, leaf beetles
Background
Paterson’s curse (Salvation Jane), Echium plantagineum, is a noxious weed of European origin found through much of Victoria. It is a Regionally Controlled Weed in all Victorian Catchment and Land Protection Regions except Mallee. Landholders in these areas must take all reasonable steps to control and prevent the spread of this weed ontheir land and the roadsides which adjoin their land.
A national program for biological control of Paterson’s curse involves the establishment of populations of the weed’s natural enemies and the redistribution of them to other sites as populations increase. A cooperative project between CSIRO and DNRE has led to the release of the Paterson’s curse taproot feeding flea beetle, Longitarsus echii, in Victoria. The flea beetle has been tested to ensure it is specific to Paterson’s curse and presents no danger tonative plants or plants of economic importance.
Description
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Adults - 2 to 4 mm long, shiny black, with a touch of bronze (Figs. 1 and 2). They have enlarged hind legs which enable them to jump considerable distances, hence the name ‘flea beetle’. The appendages, particularly the tarsi (feet) and antennae are reddish in colour. The antennae arealmost as long as the body of the beetle.
Eggs - Minuscule, reddish-brown and difficult to find.
Larvae - Slender, cylindrical, up to 10 mm long by 2 mm wide, cream in colour with a dark head capsule. Larvae arerarely seen unless the taproot is cut open.
Pupae - 5 mm by 2 mm, white to cream in colour, formed in an earthen cocoon in soil around the roots of Paterson’scurse.
Life cycle
The flea beetles have one generation per year. Adult beetles emerge from the soil in early winter and begin egg laying within a few weeks. Some adults may survive untillate in spring.
Eggs are laid on and around the crown of the plant. Larvae (grubs) hatch after about three weeks, depending on theenvironmental temperature.
The larvae initially feed on the plant crown and leaf stalks, and then descend into the taproot where they feed internally. After three months the larvae leave the root and pupate in the soil. Around one month later, they transform into adults, which remain inactive in earthen cells in thesoil until winter.
Impact
Internal damage to the taproot caused by the feeding of mature larvae is the most important impact of the flea beetle. Root damage interferes with the flow of water and nutrients from the soil to the plant, causing it to weaken. For much of the year infested plants may show no external signs of beetle damage apart from wilting and poor generalcondition.
In winter and spring adult beetles feed on the leaves, producing small “shot holes”. These holes are smaller and more irregular than those produced by the crown and root weevils, Mogulones larvatus and Mogulones geographicus, which have also been released to controlPaterson’s curse.
Adult flea beetles cause only superficial damage to the plant. Similar shot holes can also be produced by other small animals, so are unreliable indicators of flea beetle presence. For example several species of native flea beetles may feed on Paterson’s curse and related plants in summer, but their occurrence is patchy and damage to theplant is insignificant.
Releases
The Paterson’s curse taproot flea beetle was first released in Victoria in 1996. It is released onto the weed in large cages at 'nursery sites'. Populations of the beetle are expected to build up within the cages, and to be harvested for later re-distribution to other infestations. Nursery sites are selected by researchers and local NRE staff inconsultation with land owners and Landcare groups.
A release site should have a dense and persistent Paterson’s curse infestation and be connected to other neighbouring infestations so that the flea beetle can disperse more readily. The site should have a low priorityfor control by other techniques.
Integrated control
Four other species of insect which attack Paterson’s curse have been released in Victoria. The leaf mining moth, Dialectica scalariella, was first released in Victoria in 1988 and was well established by 1992. The crown weevil, Mogulones larvatus, was widely released from 1994 and redistributed from 1996 to 1998. The root weevil, Mogulones geographicus, was first released in early 1996. The stem-boring beetle, Phytoecia coerulescens, the larvae of which eat-out and girdle flowering stems, was first released in Victoria in 1997. The complementary effects of these agents are expected to make the weed less competitive. Other insects, which will attack different partsof the plant, are being investigated.
Biological control cannot totally eradicate a weed but may reduce the spread and density of infestations. In some cases control is achieved to the level where the weed is no longer of concern and no other control is necessary. More commonly, other methods are still required to achieve the desired level of control. Biological control should not be considered the complete answer to a Paterson’s curse problem. It is a technique that should be used in conjunction with other control measures in an integratedmanagement plan.
Further information
More information on Paterson’s curse is available in the The Paterson’s Curse Management Handbook, the Landcare Notes: Paterson’s curse, Paterson’s curse identification and Biological control of Paterson’s curse with the stem-boring beetle, and in the pamphlets Biological control of Paterson’s curse using the leaf mining moth and Biological control of Paterson’s cursewith crown and root boring weevils, available from KTRI.
For further information on Paterson’s curse please contactyour local NRE Catchment and Agricultural Services staff.
For further information on the biological control ofPaterson’s curse contact:
Keith Turnbull Research Institute,
PO Box 48, Frankston, Victoria, 3199.
Tel (03) 9785 0111
Fax (03) 9785 2007
email ktri@nre.vic.gov.au
Acknowledgments
Prepared by Blair Grace, Ian Faithfull and Tom Morley (KTRI) and Anthony Swirepik (CSIRO Division of Entomology), 1996. Revised December 1998. Biological control of Paterson’s curse has been funded by Meat and Livestock Australia, The Woolmark Company and NRE and is supported by the Cooperative Research Centre forWeed Management Systems.
It was reviewed by:
Keith Turnbull Research Institute, Frankston
