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This Landcare Note describes the boneseed leafroller moth, “Tortrix” sp., a biological control agent for boneseed, Chrysanthemoides monilifera. Common and scientific names “Tortrix” sp. , an undescribed species Boneseed leafroller moth Family Tortricidae, leafroller moths Background Boneseed (Chrysanthemoides monilifera monilifera) and bitou bush (C. monilifera rotundata) are closely related weedy shrubs from South Africa that were first recorded in Australia in 1852 and 1908, respectively. Both are now widely established in south-eastern Australia where they degrade native vegetation by displacing indigenous plants and animals.  Figure 1. Distribution of boneseed and bitou bush. Boneseed and bitou bush may be distinguished by the number of ray florets and by the shapes of their leaves. The ray florets look like petals. Boneseed has 4 to 8 ray florets (usually 5 to 6) while bitou bush has 11 to 13. Boneseed leaves are ovate and thin with irregularly toothed margins. The leaves of bitou bush are ovate to circular with the upper half broader than the lower half. They are fleshy and the margins are usually entire (not toothed). Boneseed and bitou bush are approved targets for biological control and a number of damaging species of insects, mites and fungi are being screened for their potential to control these weeds and for their suitability for release in Australia. All potential biological control agents are from South Africa where the leafroller is the most damaging insect on Chrysanthemoides. The Keith Turnbull Research Institute and CSIRO Entomology jointly tested this insect for host specificity in Australia and South Africa. Extensive and intensive searches in the country of origin have failed to find the leafroller on any other plant species. Two strains of the leafroller are available, one collected from boneseed and one from bitou bush. Description   Figure 2. Adult leafroller (photographs: Rachel Melland (top) and Penny Edwards (below)). Adult – forewing narrowly triangular with an acute apex, average length 9.5 mm (range 7.9 to 10.6 mm), variable in colour but usually mottled earthy brown with a darker, narrow zig-zag, band across the forewing, extending at around 60 to the leading edge of the wing. Forms with mottled forewings occur frequently. The hindwing is yellow-brown in colour with weakly marked eyespots towards the outer margin. Egg – pale yellow in colour when first laid, turning to orange, flat, oval (length 0.7 to 1.4 mm, width 0.6 to 1.1 mm) and with reticulate surface ridges. The area between the ridges is covered in a dense scurf of crystal-like scales, a feature that distinguishes the boneseed leafroller from other species. The egg batch consists of rows of eggs side by side, forming an irregular shape, and is covered with a transparent film secreted by the female during egg laying.  Figure 3. Egg batch of the leafroller shortly before hatching (photograph: Rachel Melland). The eggs are orange and the dark head capsules of the larvae are clearly visible. Larva – a caterpillar passing through five or six instars (stages), with three pairs of legs on the thorax, and abdominal and anal prolegs. The head, thoracic shield (upper side of the first segment of the thorax) and anal plate are black. Larvae of the bitou bush strain differ in having an orange head capsule. First and second instar caterpillars are olive green with indistinct tubercules (raised, hardened skin patches appearing as white spots) on all abdominal segments. Later instars have a general body colour that is dark green or dark olive-brown to black, paler on the underside, with tuberculae (white spots) in parallel rows along the length of the body. The upper side of the larva has two rows with two white spots per segment. The sides of the body have a single row with a single spot per segment and the underside has three rows each with a single spot per segment. Dorsal and ventral spots each bear 1 seta (fine hair), while ventral spots have 1 to 3 setae. The larva is a concealed feeder, found inside a shelter formed by tying together the leaves of the food plant with silk. Pupa – light to dark brown, average length 10.6 mm (range 8.3 to 12.0 mm), with a row of small spines on the upper side of each segment of the abdomen, and hooked spines on the anal segment. Pupation usually occurs in the larval shelter. There are many native species of Tortricidae, which could be confused with the boneseed leafroller, including the lightbrown apple moth, Epiphyas postvittana, a pest species which feeds on a wide variety of plants. Larvae of the lightbrown apple moth are light green in colour and the eggs are green. Adult lightbrown apple moths have a black spot in the middle of the thorax between the wings.   Figure 4. Mature larvae of the leafroller (photographs:Penny Edwards).  Figure 5. Pupa of the leafroller in the leaf shelter made by the larva (photograph: Rachel Melland). Life cycle In South Africa the leafroller has three generations per year with peaks of egg laying in July, November and late January. Adults are nocturnal and oviposit on both upper and lower surfaces of leaves of the host plant. Eggs are laid in rows in irregularly shaped batches totalling up to 80 eggs. The females on average deposit 7 batches of eggs, totalling about 200 eggs. Eggs hatch after approximately 8 days and larvae disperse immediately without eating the egg shell. Newly hatched larvae may drift on short silk threads if they are disturbed or where suitable foliage is not immediately available. They move to shoot tips to feed. Leaf margins, tissue adjacent to the leaf midrib and axillary buds are also utilised by young larvae. Larvae construct feeding shelters in the shoot tips by webbing together two or more neighbouring leaves and consume the leaves and stems from within the shelter, around the canopy. At 22.50C the duration of the larval stages is approximately 30 days and that of the pupa about 10 days. One to several pupae may occur in a single shoot tip. Adults live for an average of 14 days.  Figure 6. Damage to boneseed in South Africa by larvae of the boneseed leafroller (photograph: Aline Bruzzese). Impact Release of the leafroller in Australia is the first use of this insect as a biocontrol agent. Larval feeding on leaves, stems and bark results in the death of terminal leaves and shoot tips. Older larvae consume mature leaves and are capable of destroying all the leaf material on a plant. In outbreak situations where high densities occur on Chrysanthemoides in the summer months, the plant may be severely defoliated and weakened, or killed. Experiments conducted by CSIRO Entomology in South Africa in which the leafroller was excluded from plants by use of insecticide treatments demonstrated that the insect caused a 93% reduction in the production of fruiting heads. If three or more generations of the leafroller occur in one year in Australia then its populations should build up rapidly and the impact should become apparent relatively quickly. If there is widespread and rapid defoliation of Chrysanthemoides in Australia due to leafroller activity then revegetation strategies that reduce the risk of soil erosion and the encroachment of other weeds will need to be implemented.  Figure 7. Damage to leafy sprigs of boneseed by the leafroller (photograph: Robin Adair). Curled leaves at the tips are larval shelters. Small black pellets are the frass (excreta) of the larvae. Releases The leafroller is released in the larval stage on sprigs of the food plant which are attached to Chrysanthemoides branches at the release site. Releases are to occur at sites in Victoria, South Australia, Tasmania and New South Wales. Releases commenced in autumn 2000, with the first release at the You Yangs Regional Park in Victoria. Other biological control agents Five species of insects with potential to defoliate Chrysanthemoides have been released. Three leaf-feeding beetles, Chrysolina species, were released extensively in south-eastern Australia but have failed to establish. Nati| The bitou tip moth, Comostolopsis germana, is well-established on bitou bush in New South Wales and is reducing seed production. It is surviving despite heavy ant predation in the Adelaide Hills, but is having little impact on the weed. The larvae feed in the stem tips and destroy developing leaves, buds and flowers. The bitou tortoise beetle, Cassida sp., was first released in 1995 on the central coast of New South Wales and has established at some sites. This beetle feeds on the older foliage of bitou bush and complements the damage caused by the bitou tip moth. Two seed flies, Mesoclanis polana and M. magnipalpis, which feed as larvae on Chrysanthemoides fruit and seeds, have been released. M. polana was first released in 1996 and is causing major reductions in seed production of bitou bush throughout the range of the weed on the east coast of Australia. M. magnipalpis, targeted at boneseed, was first released in June 1998 and has not yet had a significant impact. Host specificity evaluation of a rust fungus, Endophyllum osteospermi, is being undertaken and this agent may become available for release in the future. Another agent, the leaf buckle mite, Aceria neseri, is currently being studied and tested in the high security quarantine area at the Keith Turnbull Research Institute.  Figure 8. Boneseed foliage damaged by the leafroller (photograph: Aline Bruzzese). Integrated control Biological control is not appropriate for all infestations of Chrysanthemoides. A local weed management plan should be developed for each particular area. An integrated weed management plan identifies opportunities for integrating all available control options, including biological control, in the most environmentally sensitive, economic and efficient manner. In areas where biological control agents have established, conventional control techniques may still be undertaken, but where large-scale clearance work is conducted, corridors of plants with biological control agents should be retained so that Chrysanthemoides regrowth is quickly recolonised by the agents.  Figure 9. Boneseed infestation (photograph: Robin Adair). Further information For further information on bitou bush, boneseed or the biological control program contact: Keith Turnbull Research Institute PO Box 48, Frankston, Victoria, 3199 Ph: (03) 9785 0111 Fax: (03) 9785 2007 email: ktri@nre.vic.gov.au Acknowledgements Prepared by Ian Faithfull, Aline Bruzzese and Jean Louis Sagliocco. Information on the life cycle and impact of the boneseed leafroller moth provided by CSIRO Entomology. Assistance with image processing Les Bould. Distribution map from W.T. Parsons and E.G. Cuthbertson, Noxious Weeds of Australia, Inkata Press, Melbourne, 1992. The Chrysanthemoides monilifera biological control program is a national project coordinated by the Cooperative Research Centre for Weed Management Systems and funded by the Australian and New Zealand Environment and Conservation Council (ANZECC). The host specificity testing of the boneseed leafroller moth was partly funded by the Cooperative Research Centre for Weed Management Systems. This note replaces note number BC0038 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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© The State of Victoria, 1996 - 2008.
This document was published on 26/10/2008.