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land. In 1994 Meander Valley had 114 Dairy Farms milking 19,000 cows and producing 67 million litres of milk. The Department of Primary Industry and Fisheries estimated that there is a 10% net loss of production due to ragwort. This is costing the Municipality $780,000 or on average $6842 per dairy farm, without considering the cost of herbicide, manpower and machinery in control measures. It is estimated that ragwort is costing land managers in the Municipality $2-3 million per year.
The ragwort flea beetle, Longitarsus flavicornis (Stephens), was introduced to Tasmania in the autumn of 1979 as a possible biological control agent for ragwort. During an intensive mass rearing program, adult beetles were released from November 1979 at sites throughout the ragwort infested areas of the State. This resulted in the successful establishment of field populations.
By the end of February, 1998, field surveys indicated that the ragwort flea beetle has now spread through at least two-thirds of the total area of land infested by ragwort. Within this area it is now starting to have a significant impact on ragwort.
In the south of the State it has now spread throughout most of the Huon Valley, Bruny Island and over a number of properties in the Derwent Valley. In the north west it is now well establised through large areas of the Meander Valley Municipality and has been recorded elsewhere in high numbers at Merseylea, Staverton and West Kentish. In the north east it has been recorded in high numbers at Derby, St. Patricks River and Tayene.
The rate of spread of the beetle has been substantially increased in recent years. This has resulted from a successful program to collect beetles from established sites and release them at new sites in the worst ragwort infested areas, particularly on dairy farms.
This program has involved officers of Tasmanian Institute of Agricultural Research working in conjunction with personnel from the Meander Valley Weeds Strategy.
Many properties in northern Tasmania, particularly in the Meander Valley Municipality, have serious ragwort problems and it is these locations that have been targeted for beetle releases.
By the end of April, 1998 about 1.8 million beetles had been collected and transferred to over 800 sites.
Up to this time, the number of Landcare and community groups that have become involved in the redistribution program has been restricted. This is mainly because specialised collecting equipment is needed to collect the minimum number of 1,000 beetles required for a field release, as well as collectable populations existing only in localised areas. However, suitable collection sites now exist in most districts and a number of groups and individuals have access to collection equipment and knowledge of the collection methods necessary to become involved in the redistribution program.
As the assistance of landholders will be essential to the success of the redistribution and establishment program, it is important that those involved are aware of the beetles' life cycle, its ability to control ragwort and the management practices that can be utilised to promote the establishment and build-up of populations.
Description
The adult stage is a beetle about 3mm long. Newly emerged beetles are a light brown colour, becoming darker as they mature.
 The eggs are elongated, about 0.2 mm in diameter and 0.6 mm long and light brown in colour.
 Larvae (grubs) are whitish in colour and pass through three moults or instars. Newly hatched larvae are about 1.5 mm in length and have dark head capsules. Mature larvae are about 5 mm in length and have reddish-brown head capsules.
The pupae from which adults emerge are white and just over 3 mm in length.
Life Cycle
 One generation of the ragwort flea beetle is produced each year. In Tasmania, adults are most active on the ground surface in summer and autumn. The beetles start to emerge from pupae in the soil about mid-December and eggs are laid, usually in the surface soil around the plants, three to four weeks after mating. Hatching is temperature dependent and occurs in about 17 days at 20 degrees celsius. The newly hatched larvae feed by mining into the lower stalks of the leaves (petioles), the roots and root crown.Larvae also are commonly found feeding externally on roots in the soil around the plants. Larvae feed from late summer until the end of the following spring when they pupate in the soil around the plants.
Damage to ragwort
The most significant damage to ragwort is caused by the larvae burrowing into roots and root crowns giving them a furrowed and scarred appearance. As many as 400 larvae may feed on a single plant, severely weakening the plant and ultimately causing its death.
Much of the beetles' life cycle takes place below ground and their presence is often not evident to the casual observer. However, during summer and autumn, the adult beetles are active and can be observed feeding on the rosettes, particularly on warm, still and overcast days. Although adult feeding is not regarded as having a significant detrimental effect on the plants, large numbers of beetles have caused extensive leaf damage at some sites with only ragged portions of the leaves remaining on some plants.
How effective is the beetle
Where ragwort flea beetle has established and increased in large numbers a substantial decline in the population of ragwort has occurred reducing infestations at some sites by as much as 95%.
As these sites are representative of many ragwort infested areas, it is expected that the beetle will eventually play a major role in reducing the density of ragwort over a wide area. However, it must be emphasised that control does not mean eradication. Furthermore, conditions vary from site to site which may either prevent establishment of beetles, or affect the extent and rate of control. In some of these situations it is hoped that additional stress on the plant can be achieved by the establishment of other biological control agents such as the recently established leaf and crown boring moth , or by using biological control agents as part of an integrated management program with traditional control methods.
If the estimatethat the ragwort flea beetle may now have spread over approximately 75% of the ragwort infestations in Tasmania is correct, then it can be expected that it will spread over most of the remaining northern Tasmanian areas within the next 10 years. This is considered a reasonable estimate based on survey results which show that the beetle is already established and spreading through large ares of northern Tasmania from old release sites, and the high level of establishment (at least 70%) expected at the 384 sites where releases were carried out during the 1995-98 program. These populations will eventually link with those spreading from other sites.
How long does the beetle take?
The build-up of newly released populations is a long process. At the best sites it usually takes between 6 and 8 years for beetle populations to reach levels high enough to effectively control ragwort. However, if temporarily unsuitable conditions (such as a sequence of summer droughts) prevail at the release site over several seasons it may take much longer. Once the beetles are well established in an area, the rates of spread increase, particularly if there is good rain fall in spring and early summer.
The length of time required for beetle populations to increase to high levels has caused problems at some sites. Some landholders have given up on the beetle and boom sprayed their release site with herbicide 4-5 years after release, just when beetle populations were becoming well established. Any landholder who had beetles released at a particular site some years ago and is considering whether to treat the area with pesticides should obtain advice on the progress of the beetle prior to doing so. If beetles are becoming well established, the landholder may be better off controlling the spread of ragwort in the short-term by slashing or mowing or the careful use of grazing animals. This would allow additional time for the beetle populations to increase to a level which could result in the ragwort being brought under control.
Once beetles do become established in an area and are effective, the financial benefits are immense because savings in contol costs will accumulate with time.
  Image on the left taken in January, 1994 when large populations of ragwort flea beetle were recorded at the site. Ragwort flea beetles had been released near this site 13 years earlier (October 1980). Up until this time, the area had been subjected to continuing use of pesticides. Image on the right taken in January, 1995, 14 years after the release of ragwort flea beetles. This depicts the damage that can be acheived to the ragwort plants once the beetles have established in large enough numbers.
Farming with beetles (integrated management)
If beetles have been released on property or spread into it from a neighbouring release site, their establishment and spread can be greatly assisted by observing some simple management practices.
- Careful use of herbicides
Herbicides can reduce beetle populations to low levels primarily because of their effect on ragwort. However, preliminary studies also suggest that some herbicides such as 2,4-D and the low volatile ester of MCPA are directly toxic to adult beetles. If possible, they should not be used within a distance of at least 50 m from where the beetles are active particularly at new release sites. Outside this limit, however, herbicides can still be used according to the manufacturers instructions.
In the population of beetles and non-flowering rosettes is high, wick wiping an area to kill flowering plants but leaving the non-flowering rosettes intact for the beetle is now being recommended as a suitable way of integrating the two control methods.
- Avoid excessive grazing by sheep
Excessive grazing by sheep during summer has caused problems at a number of sites. However, sheep are valuable in suppressing the spread of ragwort and can be used in release areas provided strict management practices are observed. In fact, grazing can be used to enhance the beetle's effectiveness.
As mentioned previously, the adults (beetles) emerge in mid-December and are most active above ground in summer and autumn. They need leafy rosettes for food and shelter during this period. Heavy grazing by sheep in summer and autumn reduces the food and shelter available to the adults, may remove larvae present in the leaf-stalks and in consequence is detrimental to the beetles' survival and rate of spread.
Release sites can be grazed heavily until about the end of November. This should allow sufficient regrowth of rosettes before adult beetles become active in mid-December. It is essential that sheep are then kept off the sites until about late February, or until just before the ragwort starts to seed. However, heavy grazing should be avoided because the beetles will still be active. Sheep can be used to remove the flower heads and lightly graze the foliage from late February until the end of April. By then the beetles' activity on the surface will have started to decline and normal grazing practices can be resumed.
- Other grazing animals
Cattle and horses normally avoid eating ragwort. No grazing strategy needs to be applied apart from preventing excessive trampling when stocking rates are high, particularly in areas where pastures are damp.
- Slashing and mowing
Slashing the stems at release sites in summer to prevent seeding may be used in place of grazing by sheep. The area also may be mowed provided the blades are set high enough for the rosettes to remain intact.
Additional agents
Ragwort is often attacked by a native moth, Patagoniodes farinaria (Turner), commonly know as the blue stem borer because the bluish coloured larvae bore into ragwort stems. Larvae are particularly active on flowering stems during summer. Their presence is detected by large quantities of frass (excreta) on the stem surface. This insect, where it occurs alone, does not appear to have any significant effect on the ragwort population.
Blue stem borers and ragwort flea beetles when they occur together should complement each other in controlling ragwort because the beetle larvae feed mainly below ground and those of the blue stem borer feed mainly in the stems above the ground.
A second species of ragwort flea beetle, Longitarsus jacobaeae (Waterhouse), which is better adapted to survive dry summers, was introduced into Tasmania in 1988 to be bred for field release.
This species has now become established and is spreading at several sites. It is expected that the species will also eventually play a major role in ragwort control.
Two other biological control agents of European orgin, the cinnabar moth, Tyria jacobaeae (L.), which feed on ragwort leaves and flowers, and the leaf and crown boring moth, Cochylis atricapitana (Stephens), are now being investigated. Both insects are being mass reared in glasshouse cultures and released at sites around Tasmania. At this stage it is still uncertain whether cinnabar moth will establish due to effects of predators, however, the leaf and crown boring moth has now become permanently established at several release sites and is starting to spread. The feed activities of the larvae of these insects will also complement the root feeding activities of the ragwort flea beetle larvae, resulting in faster and more effective control.
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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