Larvae of the Leaf and Crown Boring Moth can eat out the central crown of the ragwort rosettes and also bore into leaf petioles ultimately killing the plant. Ragwort flower buds and stems are also attacked which can reduce or prevent flowering and may also reduce amount of seed produced.
The leaf and crown boring moth was originally imported into Victoria from Spain in 1985 and was first released in Victoria in 1987 where it has since become established. If this species can be established in Tasmania its activities would further synergise the impact on ragwort from feeding by species of ragwort flea beetle and the cinnabar moth.
The first importation into Tasmania of the leaf and crown boring moth was made in 1994 and released into the field in the same year. The first releases were made in the Meander Valley Region in October 1995, further releases being made between that date and March 1998. Of the 20 release sites in this region, field inspections of sites that were at least a year old, in the autumn of 1998 indicated that the leaf and crown boring moth had established at 2 sites and colonies are surviving at a further 11 sites.
DESCRIPTION
Moth
The moth is 8-10 mm long and ranges from pale to dark brown in colour. It has a 1 mm wide brownish blotchy band running diagonally across the middle and end of its fore-wing and a 0.3 mm long tuft of dark scales that protrudes just behind the head. In the resting position, the wings are folded against the sides of the body with the hind-wing completely hidden under the fore-wing. Moths are most active at dusk or dawn and are attracted to light. The sex ratio males to females is 1:1.
 Egg
Eggs are flat and oval in shape, 0.5 mm long and a translucent white in colour when first laid. They become yellow during development. Eventually the dark head capsule of the developing larvae can be seen. Most eggs are laid along the primary and secondary veins on the underside of leaves. The majority are laid individually but sometimes in pairs.
 Larva
The Larva (or caterpillar) is creamy white in colour. The young larva has a black head capsule which may become light brown or tan as it matures.
 Pupa
The Pupa is light brown in colour, 7 - 8 mm long and 1.5 - 2 mm wide. It is usually formed within the plant and the site of moth emergence is marked by the appearance of the empty pupal case protruding from the crown, stem or buds.
DAMAGE
 Damage to ragwort by leaf and crown boring moth is caused by the feeding activity of the larvae. After hatching, the larvae begin mining into the plant, boring into the leaves, leaf buds, stem or crown.
Attacked ragwort rosettes may be distinguished by blemished or blackened young central shoots and the wilted appearance of side shoots, caused by larval damage to the crown. In severely infected rosettes, larvae eat out the central crown and then start boring up leaf petioles, killing the plant. Some plants survive and regrow, but with reduced foliage, and do not flower that season.
Bolting (erect growth prior to flowering) ragwort plants attacked in the stem can be identified by small tunnels entering at the leaf bud in the axils of side shoots. The tunnels often have a small pile of fine faecal material at their entrance and if the moth has emerged, a pupal case protrudes from the tunnel. Attacked flowering plants can be identified by the blackened, wilted appearance of the flower buds and/or the multi-stemmed flower crown, which branches out from below the point where the flower stalk was affected. Heavy larval infestations on bolting ragwort plants may prevent or reduce flowering and subsequent seed production. In addition, attacked plants often die due to the additional effects of secondary feeders, such as fungi, bacteria and some insects. These gain access to the plant tissue and feed on dead and decaying plant material as a result of primary damage by the larvae of the leaf and crown boring moth.
In the field, the damage to ragwort caused by leaf and crown boring moth can be confused with that caused by the larvae of a native insect that often attacks ragwort, the blue stem borer, Patagoniodes farinaria (Turner). The larva of the blue stem borer has bluish-grey stripes along its length, three of which are visible when viewed from above. The middle dorsal stripe is narrower than the other two. Younger larvae have the same stripes but they tend to be a lighter, brownish colour. The striping of these caterpillars easily distinguishes them from the uniform creamy white colour of the leaf and crown boring moth. In addition, the excrement (frass) produced by the larvae of the blue stem borer is coarse and easily visible, hanging off the stems of ragwort. Although leaf and crown boring moth attacks similar parts of the plant, the frass produced is much finer and less obvious.
Life Cycle
In Tasmania, there are two complete generations of the leaf and crown boring moth each year. However there may be considerable generation overlap. Moths of the first generation start to emerge in early spring with maximum emergence in October. The females lay up to 150 eggs. Most first generation larvae feed and develop on the ragwort plant from November with most pupating by mid-summer (January). The second generation of moths start to emerge during January with the larvae produced by these moths feeding until autumn (May). Towards the end of autumn and the beginning of winter, mature larvae enter a state of dormancy until the following spring. Before entering dormancy, larvae spin silken cocoons and change from creamy white to pink in colour. Most larvae over-winter in this dormant phase in the crowns of rosettes or under the bark at the base of senescent stems. They have also been found in the leaf buds of senescent plants and amongst dead ragwort leaves and surrounding litter. With the increasing day lengths and higher spring temperatures, the larvae become active again and pupate.
School Project
During 1998, young students in 10 Tasmania schools become involved in breeding up large numbers of moths from initial breeding stocks of 16 moths in each school, following a grant of $25,000 from the Natural Heritage Trust for a period of three years. This is the first time in Australia that attempts have been made to involve school students in a breeding up program for the leaf and crown boring moth.
In the Meander Valley Municipality, Deloraine High School and Meander Primary School were the two schools chosen to participate in this program, they worked together with the Dr. John Ireson and Wade Chatterton of the Tasmanian Institute of Agricultural Reasearch and Sandra Leighton, Consultant Entomologist employed by the Tamar Valley Weed Strategy with funding from the Natural Heritage Trust. On the 30th September, 1998, 100 moths from their breeding program, were released on a dairy farm near Meander. This was the first release in Tasmania from the schools project.
The technical text and images on this page were supplied by Dr. John Ireson, Senior Entomologist, Tasmanian Institute of Agricultural Research.
 
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