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English broom suppression with the broom psyllid | LC0157 |
Keith Turnbull Research Institute, Frankston
October, 1999 |  |
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Common name
Broom psyllid, broom bud psyllid
Scientific name
Arytainilla spartiophila (Foerster)
Homoptera: Psyllidae
Background
English (or Scotch) broom, Cytisus scoparius, is a Regionally Controlled Weed in the Wimmera, Corangamite, Port Phillip East, Goulburn, North East, West Gippsland and East Gippsland Catchment and Land Protection Regions of Victoria. It is a threat to environmental, forestry and grazing lands in these Regions and other areas of south-eastern Australia with moderate to high rainfall.
A program is under way to introduce a number of natural enemies of English broom from Europe. Extensive testing of the third of these agents, the broom psyllid, has demonstrated that it feeds only on English broom and does not attack native plants or plants of economic importance.
Description
Psyllids are also known as jumping plant lice. In appearance they are similar to aphids or tiny cicadas.
Adults – 2 to 3 mm long, light brown to light red brown in colour with variously developed markings (non-existent to dark brown) on the thorax and head. The translucent wings are folded over the body. The hind legs are adapted for jumping but are not strongly developed like those of a grasshopper. The 10 segmented antennae are thread-like and about half as long as the body.
Eggs – ovoid in shape with a short stalk; inserted singly into slits cut into the concave surfaces of young stems by the female. The exposed surface of the egg is covered with a wax layer produced by the female’s anal glands.
Nymphs – five wingless nymphal instars (growth stages), similar to the adults but flattened and wingless. First instar nymphs are greyish-green with prominent wing buds. Later instars become progressively orange-brown and grow from 1.4 to 1.9 mm in length.
The broom psyllid should not be confused with broom aphids that may at times cause extensive marks on the foliage and damage to broom seedlings. Aphids have antennae with 6 or fewer segments.
Figure 1. Adult broom psyllid on a broom stem.
Figure 2. Fifth instar nymph of the broom psyllid.
Life cycle
The broom psyllid has only one generation per year and a long period of winter inactivity (diapause) lasting 5 or 6 months in the egg stage. Mature adult psyllids appear in late spring and early summer and live for 3 to 4 weeks. They are very active and readily move to new broom bushes. Egg laying occurs over the summer period. Female broom psyllids make many trial incisions with their ovipositors in addition to those in which they place their eggs, so that a broom stem containing eggs has a scarred surface. The first instar nymph is fully formed inside the eggshell by the commencement of diapause, 4 weeks after the egg is laid.
Egg hatching coincides with the bud-burst of broom plants. Individual eggs hatch quickly but the hatching period is protracted and the emergence of young nymphs may continue for several weeks. This results in a wide overlap of nymphal stages. The newly hatched nymph emerges through the oviposition hole made by the female during egg laying. It then creeps along the stem until it finds a bud where the scales are separating and crawls in between the scales to feed. Adults emerge 4 to 8 weeks later.
Impact
Both the adults and nymphs feed on the buds and other actively growing parts of English broom by inserting their mouth parts into the plant, sucking sap and damaging cells. Their saliva is probably toxic to local tissue. The broom psyllid is host-specific and poses negligible risk to other plant species.
High populations of the broom psyllid occur on broom bushes in Europe causing severe damage. In the United Kingdom, bushes with the highest densities of psyllids per bud are usually stunted with little shoot growth. The impact of the broom psyllid varies between years and sites, with the most damage occurring on young actively growing plants. The psyllid will contribute to the reduction in vigour and seeding capacity of English broom in Australia.
Adult psyllids are strong fliers and very mobile, and emigration occurs readily, even at low population levels. Once populations are established in the field, new bushes should be quickly colonised.
Releases
The broom psyllid was first released in Australia in 1994. Releases have been made in New South Wales and Tasmania at over 25 sites. The first releases in Victoria were made in spring 1999.
The psyllid is released in spring when broom is actively growing. Bouquets of broom hosting 1000 adult psyllids in total are wedged into the foliage of the release bushes, approximately one bouquet per bush. Psyllids should not be released if the weather is windy or wet.
Appropriate release sites have a dense population of English broom including young, actively growing plants. The infestation should be at least one hectare in size with adjoining infestations to enable dispersal of the psyllid. The site should be excluded from other weed control measures to encourage psyllid establishment.
Integrated control
The broom psyllid alone will not control English broom. A suite of other biological control agents is expected to complement the damage caused by the psyllid and impose added pressures on broom infestations.
There are two additional English broom biological control agents approved for use in Australia. The broom twig-mining moth, Leucoptera spartifoliella, was first released in 1990. Larvae of this moth mine broom stems, causing dieback and reduced growth. The broom seed-feeding beetle, Bruchidius villosus, was first released in Victoria in 1998. The larvae of this beetle burrow through broom pods and feed inside the developing seeds, which are consequently destroyed.
Two further agents are currently under investigation, the seed-feeding weevil, Exapion fuscirostre, and an eriophyid gall mite, Aceria genistae. Host specificity testing of these potential agents is still under way and they have not yet been approved for Australian release.
Biological control cannot eradicate a weed, it can only 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, however these need not be used so frequently or intensively. Biological control should not be considered the complete answer to an English broom problem, but can be used in conjunction with other control measures in an integrated weed management program.
Further information
For further information on the management of English broom please contact your local land management agency staff or:
Keith Turnbull Research Institute,
PO Box 48, Frankston, Victoria, 3199.
Phone (03) 9785 0111 Fax (03) 9785 2007
Email Kate.McArthur@nre.vic.gov.au
Acknowledgments
Prepared by Kate McArthur and Ian Faithfull.
Figures from The Biological Control of Weeds Book – A New Zealand Guide, courtesy of Manaaki Whenua Landcare Research New Zealand Ltd.
Biological control of broom in Victoria is funded by NRE’s Catchment Management and Sustainable Agriculture and Parks Flora and Fauna Divisions, the Australian Alps Liaison Committee and Parks Victoria. The biological control of broom project is supported by the Cooperative Research Centre for Weed Management Systems.
This note replaces note number BC0023
The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.
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