1. At least 30 species of insects and other invertebrates are totally dependent on Ragwort as their food.
2. Many other species of insects which eat Ragwort, or require the nectar and pollen from the flowers, can also use alternative plants. However, Ragwort is often significant in supporting viable populations, especially in districts where such alternative plants may be absent or too scarce.
 |
| Six spot burnet
(Zygaena filipendulae)
© Roger Key |
It must be emphasised that Ragwort is a major nectar source for many insects, especially:-
- Solitary bees (at least 30 species: 38 cited in one list).*
- Solitary wasps (at least 18 species; not the sort to harm people).
- Hoverflies (many species).
- Conopid flies (parasitic on solitary bees and bumblebees).
- Butterflies (Small Copper, particularly where other flowers may be scarce)
- Moths at night (including at least 40 noctuid moths).
3. Ragwort is among the select few plants listed in the Weeds Act (1959). The listing was primarily concerned with control where agricultural production may be affected by its presence, especially its toxicity to grazing stock.
4. In 2003, the Ragwort Control Bill has been going through parliament. A Defra code of practice has been produced that will be backed by enforcement of Ragwort control where toxicity is perceived as sufficient risk. In particular, this covers land grazed by horses and hay fields supplying their fodder (these days largely a recreational rather than agricultural issue).
5. Both insect faunas and horses (and other farm animals) can co-exist provided control measures are targeted where really needed. In many situations Ragwort is doing no harm.
6. If the richness of the fauna is to have a future, the current over-reaction, indeed hysteria in some quarters, needs to be defused. Public and other bodies are seemingly being pressured beyond limits of tangible problems, and the horse fraternity and general public are encouraged to eliminate Ragwort, which in practice often means any plant that looks vaguely similar.
It's amazing:- The future of so many species is now dependent on an understanding of sustainability: how to make use of the countryside and town whilst maintaining biodiversity.
Ragwort: About the Plant
1. Nineteen species of the Ragwort genus, Senecio, occur in the wild in Britain, but most of these are garden escapes or other introductions.
2. The main 'weed' species is the native Common ragwort (Senecio jacobaea). This thrives where bare ground or thin vegetation allows the development of seedlings into rosettes of leaves splaying out sideways. Later (usually the next year) the rosette develops into a flowering shoot which can tolerate being among other tall vegetation.
Overall Common ragwort supports the most specialist insect species, with the look-alike native Hoary ragwort (Senecio erucifolius) highly significant in being preferred by some insects.
3. However, there are other widespread Ragworts with similar sized flowers which can be confused with Common ragwort.
Marsh ragwort (Senecio aquaticus), is not aquatic but occurs locally in wet unimproved fields. The growth form is less tall and the flowering shoots are more splayed-out. Current information suggests that this supports fewer species of special insects but remains important for flowers.
Oxford ragwort (Senecio squalidus), is an introduced plant which has become very widespread as a weed along railway lines and rubbish dumps. Its growth is loosely bushy. At least some insects feed upon it and the flowers are popular with insects.
4. The New Atlas of the Flora of Britain and Ireland (2002) shows Ragwort as native and states that ‘the distribution of S. jacobaea is unchanged from the map in the 1962 Atlas’.
5. The most recent national Countryside Survey (a national scientific study funded by Government) found no specific evidence of an increase in Ragwort in fertile or infertile grassland (i.e. grazing land) during the period 1990 to 1998. The Countryside Survey did show a significant increase in the frequency of Ragwort in lowland woods and on arable land over that period, but these are both habitats where Ragwort abundance is comparatively low and which are not frequently grazed by horses. The perceived increase in Ragwort abundance seems to be simply a result of increasing awareness resulting from the anti-Ragwort campaign.
6. Most of the other widespread native species of Senecio are groundsels. These often have inconspicuous flowers with poorly developed petals, whereas Ragworts have larger bright yellow petals. Grounsels support a relatively poor fauna, and the flowers are little use to insects such as bees. The Sticky groundsel, Senecio viscosus, is used by a few specialist species and the moderately developed petals make the flowers mildly attractive to insects.
7. Additionally there are some rare native Senecio. Notably the Fen ragwort (Senecio paludosus) (which grows to 2m in height) and the Welsh groundsel (Senecio cambrensis) (an endemic species of waste ground and waysides).
8. It is important to realise that there are other plants with a roughly similar growth-form and yellow flowers. Traveling in a car or on a train can give a false impression that Ragwort is more widespread than may actually be the case. Even on the ground, with limited botanical knowledge it would possible to be confused as to whether plants are Ragworts or not, let alone which Ragwort species. Tansy (Tanacetum vulgare), St. John's Wort (Hypericum spp.)and Hawkweeds (Hieracium spp.) are among the plants destroyed by mistake, putting at risk their accompanying invertebrate faunas.
9. Ragworts have their legitimate place as part of Britain's biodiversity, together with the large wealth of insects and fungi that they support. A degree of tolerance where these plants are not a tangible threat to horses is all that is sought.
Insect Fauna in Summary
1. Ragwort is one of the most important plants in the countryside and on urban waste ground in terms of number of species of insects it supports.
2. At least 77 insect species have been recorded eating Ragwort leaves or living in the stems and flowers About 52 of these are known to regularly feed on Ragwort as a significant foodplant.
3. More importantly, 30 species of invertebrate are confined to Ragwort as a foodplant. This is a high total for a plant and the great majority are confined to Common ragwort S. jacobaea, the main so called injurious weed or the closely similar Hoary ragwort S. erucifolius.
7 Leaf Beetles
12 Flies Including attractive picture-winged flies.
1 Macro Moth The Cinnabar moth
7 Micro Moths
1 Aphid
1 Thrip
1 Mite
A further 22 species rely very heavily on Ragwort as a foodplant.
Seven of the 52 highly reliant species are Nationally Scarce (three beetles, one fly and three micromoths); and three species are of Red Data Book status.
These figures are in general accord with those published by English Nature and Butterfly Conservation but are more stringently focused on species dependent on Ragwort. [Thus five Red Data Book species applies to species that eat Ragwort among a range of other plants (where available). The figure of 22 thrips is derived from earlier literature that does no accord with more recent specialist statements on Ragwort dependence.]
4. Most breed in flower/seedheads or stems so Ragwort control by uprooting of flailing can destroy the required condition for these insects.
5. In addition to those species feeding directly on Ragwort, the nectar in Ragwort flowers provides fuel for more than 117 species (English Nature figure). This includes:-
30 species of solitary bees, or more, utilise Ragwort.
Many hoverflies and other flies.
Butterflies by day, including the Small Copper.
Moths at dusk and during the night (e.g. 40 species of noctuid moths)
Two species of bee are particularly reliant on Ragwort as a foodplant.
6. Additionally, many of the above insects have insect parasites. The exact number of species has still to be determined, but the reported 29 species falls well short of the likely true figure.
7. Survival of such parasitic insects not only depends on continuity of the presence of plants in the right state year by year, but also on the presence of enough flowers/plants to support a viable population of the host insects.
8. Ragwort is not just important for the invertebrate populations of SSSIs (Sites of Special Scientific interest). Many key pollinator species rely on the presence of Ragwort in the wider countryside to keep going when crops are not in flower. Also without nectaring sources in-between SSSIs the dispersal of nectar dependant species between sites would become harder.
9. Disruption of continuity is a major reason why the fauna is already impoverished in many districts, for instance six species of bumblebee have declined in distribution by more than 95% in the last 25 years, largely as a result of the loss of flowers from the countryside.
10. Invertebrates need a continuity of a reasonable quantity of Ragwort plants, and control should be limited to where it is strictly justified.
11. Campaigns to eradicate Ragwort from whole districts, even where Ragwort is not a genuine problem to horses, threaten to exterminate 30 or more species of plant eating insects, and threatens the local viability of many more. This is at odds with Local Biodiversity Action Plans whose remit is to maintain biodiversity at local (and national) scales and does not comply with the Ragwort Code which requires risk assesments to be undertaken.
Ragwort Control
1. In some circumstances Ragwort does need control but more widely the issue can be hyped-up to result in over-reaction. The purpose here is to look at the facts, especially in relation to the high profile concern over toxicity to horses.
2. The toxins (pyrrolizidine alkaloids) in Ragwort can cause liver poisoning. It is a cumulative poison, eventually leading to the rather rapid onset of symptoms which precede rapid death. The plant has the alternative name Stagger Weed, referring to one of the more obvious symptoms. The lethal volume of Ragwort is said to be 7% of body weight for horses. Cattle are prone, sheep apparently less so (although it is difficult to find solid evidence of any fatal effects on other livestock). Young plants are less toxic than well grown ones.
3. Ragwort poisoning symptoms are variable and resemble the symptoms of a number of other diseases and injuries. The number of deaths of horses in Britain due to Ragwort poisoning was 10 reported incidents in 1990 according MAFF published figures. According to the British Horse Society (BHS) the most recent figure is 6,500 per year with the situation getting worse.
Wildlife & Countryside Link (a consortium of most of the main voluntary conservation and countryside organisations, including Buglife) regards the statistical basis of the BHS/BEVA ragwort linked horse death analysis as falling far short of the necessary rigor. Moreover, there would appear to be no supporting evidence that there is a major problem in other western European countries.
1. The British Horse Society (BHS) claim that 6500 horses are dying every year from Ragwort poisoning.
2. However, Ragwort poisoning can only be confirmed by dissection of the liver.
3. The BHS data is not based on confirmed data but the suspicions of vets. In addition, the statistical analysis is at best selective.
4. The survey asked British Equestrian Veterinary Association (BEVA) members how many suspected cases of Ragwort fatalities they had seen in 2002. 4% of BEVA members responded saying on average they had seen 3.37 cases. The 3.37 was then multiplied by the membership of BEVA (1,945) to give an annual total of 6,553 cases.
5. As anyone with a science degree will tell you, this is an absurd approach. In the first place, vets who did not encounter any Ragwort poisoning would be unlikely to respond to a survey about Ragwort poisoning as they would not consider it to be an issue. For all we know 96% of BEVA members may believe that Ragwort poisoning is an exceptionally rare factor in horse deaths.
6. Therefore, a more honest reporting of the survey results would be that at least 283 horses were suspected of dying of Ragwort poisoning in 2002.
7. However, in recent years there has been an increasingly vocal campaign against Ragwort, in many cases driven by those who would benefit financially from an increase in Ragwort control or monitoring.
8. If you tell vets that hundreds of horses are dying every year from Ragwort poisoning they are more likely to suspect Ragwort poisoning as a cause of horse death. The more horse owners who ask vets ‘do you think it is Ragwort poisoning’, the more yes answers there will be.
9. Therefore, one would expect a year on year increase in the numbers of suspected Ragwort associated horse deaths as a natural positive feedback loop.
Clearly any Ragwort poisoning death is a tragedy to both horse and owner. Undoubtedly some poisoning incidents in Britain can genuinely be attributed to Ragwort, but the scale of claimed incidents seems highly improbable.
4. Horses are prone to Ragwort via two main routes.
- Grazing in fields containing Ragwort. Since the plant is toxic, horses will avoid the plant if possible; this is why Ragwort can reach pest levels of abundance on horse grazed pastures. The problem really arises where paddocks and fields are over-grazed, resulting in the animals being desperate enough to eat even toxic plants. Moreover, over-grazing opens up the turf to reveal bare ground which is ideal for Ragwort seed germination. To this extent, horse owners can generate the very problem that they wish to avoid. Cattle graze less closely and are rarely subject to such over-stocked conditions. In essence cattle and horses are able to co-exist with some Ragwort providing stocking levels are not overdone.
- The main, and more insidious, problem is the presence of Ragwort in gathered forage, mainly via hay. The plant is still toxic when dead, but horses are not so able to detect and avoid it. There are, however, two solutions. Hay from fields with Ragwort should not be fed to stock or horses. Where confidence is lacking, it is possible toss and shake through the hay to remove worrying material (it would seem that missing the occasional shoot should not be too critical).
5. The most appropriate solutions to the problem of Ragwort poisoning are; firstly the proper implementation of Agriculture Act 1970 and Feeding Stuffs Regulations 2000 in which regulation 14 makes it an offence to sell feeding stuff contaminated with dangerous material; and secondly improved management of horse pastures, using established management techniques (e.g. rotation and reduced grazing pressure) to minimise the Ragwort content.
6. A letter in The Sunday Telegraph (3 August 2003) by Frances Wolferstan BA, Vet MB, MRCVS, addresses what he refers to as 'a nationwide outburst of hysteria' towards Ragwort. He points out:-
- Horses and cattle will only eat distasteful Ragwort if they are half-starved on pasture that is bare of almost anything else.
- Even in the agricultural depression of the 1930's and Second World War, Ragwort poisoning was not a major problem, yet working horses were in general use. In those pre-herbicide days, Ragwort was controlled by pulling, or using sheep to graze off young plants.
- No good stocksman would leave animals in a bare pasture with Ragwort. He felt it hard to believe that 6,500 deaths a year could be due to such a cause.
- Ragwort in hay is normally rejected by horses, and is easily removed by the groom or owner,
- The main problem could arise with silage incorporating Ragwort.
- He suggests that, in view of the high number horse deaths attributed to liver damage by Ragwort poisoning, it is time to look for other possible toxins. Pesticides added to grain to control weevils and mites is one possibility.
7. A further worry is seed dispersal from ground adjacent to fields grazed by horses or used for hay to feed to horses. Though the seed is wind dispersed, a study showed that only 0.5% became airborne and that only a tiny fraction reached 40 yards from the parent plant even down wind (cited in Harper & Wood, 1957). Whilst one cannot conclude that seed never travels more than 40 m, there is seemingly no a need for extra wide buffer zones. Seed dispersing onto cropland will be negated by herbicides.
8. It has been the case for many years that Ragwort has been controlled on some nature reserves. An excessive carpet of Ragwort over a wide area, especially of Common ragwort, is not desired by conservationists or farmers. In some instances the control by pulling or flailing may have been regrettably over-done, risking elimination of part of the special fauna (species that need stems, flowers and seedheads). But the principle of applying control where ragwort has become near dominant is well established.
9. What is sought is a tolerance of Ragwort in locations and reasonable quantity where it is doing no real harm.
- On urban and rural uncultivated land.
- Road verges, bye-ways, even bridle-ways. In most circumstances horses are not going to stop to eat distasteful plants.
- In pastures which are not destined to reach the over-stocking level which may drive animals to eat even plants which are unpalatable.
- On land that has important Biodiversity associated with the Ragwort plants.
What is 'a reasonable quantity' of Ragwort? An inevitable question, but one with no neat answer since so much depends on local circumstances and the richness of the fauna. An annual appearance of 25- 50 decent sized flowering plants may be a fair minimum for bees, though more than 100 plants would be more viable for a self contained overall fauna within a few hundred yards or 'a site'. The best faunal districts are likely to contain many more plants, often as a group of related smaller stands of Ragwort (supporting metapopulations of insects).
10. The Ragwort Control Bill Act started as a Private Members Bill and has a curious history whereby Defra omitted to consult the conservation NGOs during the initial stages of the Bill. When objections were raised by Wildlife & Countryside Link, the momentum of and expectations for the Bill were running high. None-the-less, the Bill only got through its Second Reading through in the House of Lords by bringing in numbers of peers who probably would not have voted otherwise, and the Reading was then only passed when the wildlife amendments were withdrawn.
The objections centered on:-
a) That Ragwort and its fauna is part of Britain’s wildlife and ought to be viewed positively.
b) The claim that Ragwort was becoming more plentiful could not be substantiated since BRC data suggested otherwise. Hence, if there were a genuine increase in horse poisoning, there is no parallel underlying cause – i.e. an increase in the poisonous plant.
c) The solution was better horse husbandry, including sensible care for grassland floras by not over-grazing and producing ragwort free hay crops.
d) The data for numbers of horse deaths attributed to Ragwort poisoning was not statistically valid, both as regards data assembly and proof that attributed deaths were necessarily due to Ragwort poisoning as opposed to other causes with similar symptoms.
e) Efforts at Ragwort control were likely to embrace other Ragwort species and other plants that could easily be mista ken for Ragwort by people lacking sufficient botanical knowledge.
Now part of our legislation, the Ragwort Control Bill is implemented through a Code of Practice that provides guidance on how to prevent the spread of Ragwort http://www.defra.gov.uk/environ/weedsact/default.htm
The Code states that ‘common ragwort and other ragwort species are native to the British Isles and are therefore an inherent part of our flora and fauna, along with invertebrate and other wildlife they support. The Code does not propose the eradication of common ragwort but promotes a strategic approach to control the spread of common ragwort where it poses a threat to the health and welfare of grazing animals and the production of feed or forage.’
The premature action by some County Councils (e.g. West Sussex County Council 2003) has already led to major campaigns to eradicate the plant from roadsides and many other places where genuine risk from poisoning may often be improbable.
11. Just as horse owners have sought understanding of their genuine concerns, so to their understanding is sought of the biodiversity at stake. There ought to a compatibility of objectives if the need for Ragwort control is not over-played, and for that matter if the quantity of Ragwort for conservation needs is not over-stated. The objective is to ensure that in any district there is a place for both horses and the special wildlife of Ragwort.
Insect Fauna in Detail
The following list represents the best available current knowledge, but is likely to be incomplete as yet.
Many species of insect may be found on Ragwort (Senecio spp.) but some may have only a casual relationship, such as just sitting there, or a predatory insect that will run about on any plant available. Of those insects that eat Ragwort, it is necessary to separate those species that will eat many types of plant from those that are specific to Ragwort or which have relatively few other foodplants. Ragwort fauna as given in literature thus needs to be treated with caution. The listing here only includes the most significant Ragwort feeders.
Recent evaluations are in the region of 77 species of insect that eat Ragwort, and 177 species that visit the flowers. In addition, the fauna includes the parasites of these species. At least 29 insects are known to be parasitic on Ragwort eating insects (the Ragwort specific Cinnabar moth has 11 parasites, plus three parasites of those parasites, and that is just the parasitic wasps), but for the most part these inter-dependent faunas have not been studied sufficiently to know how many species are involved.
Table 1 – Numbers of invertebrates using Ragwort as a foodplant in the UK (pollinators and nectar feeders not included)
| Red Data Book
(1-3) | Nationally
Scarce
(1-3) | Ragwort Specific | Ragwort Major | Ragwort significant | Senecio sp reported* |
| Beetles | | 3 | 7 | 1 | 1 | 5 |
| Flies | 1 | 1 | 12 | 1 | 5 | 7 |
| Macromoths | 1 | | 1 | 4 | | 25 |
| Micromoths | 1 | 3 | 7 | 4 | 4 | 2 |
| Bugs | | | 1 | | | 16 |
| Thrips | | | 1 | | 2 | 3 |
| Mites | | | 1 | | | |
| Others | | | | | | 3 |
| Total | 3 | 7 | 30 | 10 | 12 | 61 |
* Species in this category are not listed in detail here or included in the first two columns.
Total Ragwort specific + major + significant = 52
Others reported, including a few on groundsels = 61
Plus
Flower visitors for nectar or pollen
e.g., - 40 noctuid moths
- about 30 solitary bees, including two with high dependence on Ragwort
- 177 species overall (English Nature provisional/incomplete figure)
Parasites of above species
(very incompletely known) Ragwort only + main = 50 (minimum estimate)
Biocontrol
The main insects that can devastate populations of Ragwort are the Cinnabar moth and the flea beetle Longitarsus jacobaeae. Some of the fly larvae and moth caterpillars have the capacity to cause loss in seed production. The remaining fauna collectively impact upon the health and vigor of Ragwort, though the significance will depend on local circumstances. On the whole, districts where Ragwort is always present should have the most complete insect faunas, thus best balanced to continuously effect control. It is usually where poor land management allows excessive colonisation by Ragwort seed that the man made problems arise.
Biocontrol of Ragwort using British species has been attempted where the plant has become an introduced pest in such countries as North America and New Zealand. In Britain natural biocontrol can operate, but usually there is a cycle whereby strong suppression of Ragwort resulting in a collapse in the insect populations, allowing Ragwort to recover. It is also the case that the presence of a range of parasites of these insects in the UK also limits the populations of the Ragwort feeders, preventing them from having the impact on Ragwort populations that the same species can have if introduced into an environment there their parasites do not exist. It may be noted that cinnabar moth larvae may strip plants completely but the roots usually managed to shoot again the next year; the above flea beetle actually kills plants before they can flower.
Ragwort Fauna lists
The lists below are categorised as follows:-
Bold Ragwort specific (29 insects plus one mite).
Underlined Ragwort major - only one other main foodplant, or Ragwort the main plant at least locally.
Plain Ragwort significant foodplant at least in some areas, but polyphagous (eats a number of alternative foodplants).
BEETLES
Six species of Longitarsus are specific to Senecio (a further species is polyphagous). These are flea beetles, so called since they jump if disturbed. They are mostly 1.8-2.5 mm long, but a few are as much as 3.5 mm. There is also a Ragwort specific species of Phyllotreta, which is also a flea beetle. Also a phalacrid that may be specific.
Olibrus corticalis (Phalacridae). On Senecio - only confirmed plant in Britain but potentially on a few others (RES key).
Phyllotreta nodicornis (Leaf beetle)
 |
| Leaf beetle (Phyllotreta nodicornis)
feeding on Weld (Roseda luteola)
© Malcolm Storey |
Larvae at roots of Senecio jacobaea and Reseda lutea.
Recognition Adult bronze coloured, body length 2-2.8 mm.
Longitarsus dorsalis (leaf beetle) Nationally Scarce B
 |
| Leaf beetle (Longitarsus dorsalis)
on Ragwort © Roger Key |
Adults nibble small round holes in leaves from lower side, usually leaving the upper epidermis intact. In spring (March-June), adults at rosettes, hiding under leaves inert in cold weather, or very actively hopping-off if disturbed in warm weather. Adults are also found in the autumn (September-December, presumably hibernating though the winter). The beetle is distinctive in the genus, being black with a partly or entirely yellow thorax and broad yellow sides to the elytra.
Habitat. Thrives best where rosettes, even tiny ones, are on bare ground as part of pioneer vegetation as in limestone quarries and coastal cliffs, but also occurring in grassland and in woodland rides. Southern, including Peterborough and East Anglia.
Longitarsus gracilis (leaf beetle)
Adults An entirely yellow species except for the antennae being quite dark towards the apex, and sometimes with the thorax and elytral suture line only slightly darker.
Longitarsus ganglbaueri (leaf beetle) Nationally Scarce A
Adults recorded from April to December, presumably hibernating.
Habitat coastal shingle, and disturbed ground, including disused quarries. Widespread in England and Scotland (not Wales): difficult to separate from related species so may be under-recorded. Head black, thorax non-metallic reddish, elytra lighter with suture between them darker, underside black,
Longitarsus jacobaeae Ragwort flea beetle
Adults Unusually broad species with strong elytral shoulders: reddish yellow with darker apex to antennae and sometimes with some darkening on the hind femora.
Biology Eats 'shot holes' in rosette leaves. Lays eggs in soil near plants. Larvae feed on leaf petioles and root crowns, causing root crown to turn brown and die. Pupates in soil in late spring. Adults from June-December. This beetle can severely damage populations of Ragwort, though in a less conspicuous fashion than the cinnabar moth.
Habitat Widespread on stands of Senecio jacobaea.
Longitarsus ochroleucus (leaf beetle) Nationally Scarce B
Adults on Senecio squalidus, and probably some other species.
Nibble small round holes in leaves from lower side, usually leaving the upper epidermis intact. A pale yellow-brown species with hind femora black or pitchy red: a long tibial spur.
Habitat includes a chalk pit and assumed to require disturbed ground and grassland. Widespread up to SE Scotland, locally common.
Longitarsus succineus (Chrysanthermum flea beetle)
On various composites, including Ragwort. Eats rosette leaves, the holes producing a lacy appearance.
Adults Elytra yellow, hind femora yellow, antennae yellow or only slightly darker at apex.
Longitarsus suturellus(leaf beetle)
Adults Mid-line where the darkish elytra meet is darker, and the head is black and the thorax metallic black to pitchy red; the underside is black.
Indicative rather than definitive field key to Longitarsus.
(need to ensure true host plant: see Kevan (1967) for a key to this large genus)
1. Elytra (wing cases) black with broad yellow lateral margins. dorsalis
- Elytra without this pattern. 2
2. Predominantly yellow or reddish body, even beneath. 3
- At least black underneath or on head. 6
3. Hind femora (fat thigh segment) yellow or reddish. 4
- Hind femora black or pitchy red. ochroleucus
4. Body entirely reddish yellow (apex of antennae and sometimes hind femora darker). A relatively broad species, with the tibial (shin segment) spur short. jacobaeae
- Body yellow or yellowish brown. 5
5. Antennae markedly dark in apical (end) part. gracilis
- Antennae at most only faintly darker in apical part. succineus
6. Thorax (body segment between the head and elytra) metallic. suturellus
- Thorax not metallic. ganglbaueri
FLIES
Twelve species are host specific to Ragwort and five are polyphagous. The most noteworthy ones are the four picture-winged flies, since one is Red Data Book, another Nationally Scarce, and they are also pretty, especially the largest one Icterica westermanni. It should be noted that most breed in flower/seedheads or stems so control of so called noxious weeds by uprooting of flailing can destroy the required conditions for these insects.
Whilst the hoverfly and the picture-winged flies are fairly easy to identify, the rest require rather more demanding keys and a microscope. Galls are easier to identify.
Campiglossa malaris (Picture-winged fly, Tephritidae) RDBK
Mainly on Senecio erucifolius, also Senecio jacobaea; believed to breed in the flowerheads. Adults July-August. Very local in Kent.
Habitat Chalk grassland, coastal shingle and other dry sites.
Recognition A small species with brown and white mottled wings. A number of other species look similar and may casually sit on Ragwort.
Cheilosia bergenstammi (hoverfly)
Larvae in the roots of Senecio jacobaea (+ S. erucifolius ?)
Pupation probably in surrounding soil
Adults at flowers of host plants, sometimes at other flowers.
Recognition Adult about 1 cm body, black with pale brown hairs, antennae orange, hind tibia yellow with black median ring). Larva with characteristic fused twin-tube hind spiracles.
Contarinia aequalis (gall midge)
Swollen unopened young flowerhead with one or several yellow to pink larvae. Local.
Contarinia jacobaeae (gall midge)
Swollen pear-shaped older flowerhead which may have some florets. Larvae cream-white to orange, between achenes and in receptacle beneath, can 'jump' when extracted. Widespread.
Icterica westermanni (Picture-winged fly, Tephritidae)
Nationally Scarce B
 |
| Picture-winged fly
(Icterica westermanni)
© Roger Taylor |
Larvae and pupae in flower/seed heads of Senecio erucifolius & S. jacobaea.
Adults Late July-mid August by sweeping Ragwort, the adults being well camouflaged on the plant.
Habitat Open grassland, usually dry. Local in the South, south Midlands and East Anglia.
Recognition A large rather spectacular orange-brown species with heavily mottled wings.
Liriomyza erucifolii(fly, Agromyzidae)
 |
| Liriomyza erucifolii feeding in a Ragwort leaf
© Willem Ellis |
Leaf mine in Senecio erucifolius and S. jacobaea, forming an irregular linear mine normally adjacent to leaf edge.
Habitat. Recorded from Scratch Wood, Middlesex
Melanagromyza aeneoventris (fly, Agromyzidae)
Stem mine in Senecio jacobaea and Circium spp.,
Habitat. Seeming varied, widespread at least in south, extending to Scotland and Wales.
Melanagromyza dettmeri (fly, Agromyzidae)
Stem mine, polyphagous in composites, including Senecio erucifolius, S. jacobaea, inside stem and pupating in stem. Habitat varied, England and Scotland.
Melanagromyza eupatorii (fly, Agromyzidae)
Stem mine, polyphagous in composites, including Senecio jacobaea. Its fenland sites suggest Eupatorium cannabinum could also be a host in Britain (but Inula conyza and Chrysathemum leucanthemum of continental literature may not be relevant).
Habitat. Fens: Chippenham Fen and Woodwalton Fen.
Napomyza lateralis (fly, Agromyzidae) Stem mine, polyphagous in composites, including Senecio vulgaris. Other plants mainly chamomiles (Anthemis and Matricaria), marigold (Calendula), Bidens and also garden Dimorphotheca. Widespread and common.
Ophiomyia senecionina (fly, Agromyzidae)
Stem mine in Senecio erucifolius and S. jacobaea, forming external mine and pupating in mine.
Habitat. Box Hill, Surrey. [? Red Data Book status]
Phytomyza alpina (fly, Agromyzidae)
Leaf mine in Senecio jacobaea (long, irregular linear).
Habitat. Boreoalpine species, common in Scotland; also in northern England and the Burren in Eire.
Pegohylemyia jacobaeae Ragwort seed fly (Anthomyiidae)
Larvae predatory on other fly larvae in flower heads of Senecio erucifolius & S. jacobaea. [genus may be cited as Botanophila]
Pegohylemyia seneciella (fly, Anthomyiidae)
Larvae in flower heads of Senecio jacobaea, producing a cone of froth, which dries, in the middle of the flower. Found where Ragwort plants are few; in large stands there is greater probability of predation by Pegohylemyia jacobaea.
Sphenella marginata (Picture-winged fly, Tephritidae)
Larvae and pupae in flower/seed heads of Senecio aquaticus, erucifolius, S. jacobaea, S. viscosus and S. vulgaris. Flowerhead extra broadened at base.
Habitat Though widespread inland, it is generally commonest on the coast. It can be abundant where S. viscous is plentiful on coastal landslips. England as far north as Liverpool-Hull, and Wales.
Recognition A moderately small species with a very characteristic bar across the wing before the apex.
Trupanea stellata (Picture-winged fly, Tephritidae)
Larvae and puparia in flower/seed heads of Senecio.
Habitat Widespread in England as far north as Sheffield, also coastal Wales and Solway. Very scarce inland, with best clusters of records in London and to the west, Warwickshire and the Breck. Strongest on the coast, especially Kent, may actually be Nationally Scarse.
Recognition One of the few species with only a star-like dark patch on the wing towards the apex. Trupaea is an especially small delicate species (another species is exceedingly rare, host plant unknown): Tephritis cometa has a similar wing mark but this is larger and more robust.
Trypeta artemisiae (Tephritidae) Leaf miner in Senecio, Achillia ptarmica, Artemisia, Eupatorium, Tanacetum and perhaps some other composites.
Trypeta zoe (Tephritidae) Leaf miner in Senecio erucifolius, S. jacobaea, S. squalidus, S. vulgaris, plus Artemisia, Eupatorium, Tussilago, Petasites; also garden Aster and some other composites.
MACRO MOTHS
There are many moths for which Ragwort is listed or implied as a foodplant, including a number of pug moths. Five species below are especially relevant.
Eupithecia virgaureata Golden-rod pug (geometrid moth)
Larvae On flowers of Solidago virgaurea and Senecio jacobaea, as two broods in July and September-October (only larvae of the second brood have been found in the wild).
Adult May-June, August. Widespread but local.
Heliothis peltigera Bordered straw (noctuid moth).
An immigrant that only comes to Britain some years, and many succeed in having two generations here.
Polyphagous but Senecio viscosus is apparently the most frequently reported wild plant.
Phragmatobia fuliginosa Ruby tiger (arctiid moth).
Larvae Polyphagous but in some districts Senecio jacobaea is a significant foodplant (West, 1986), and the caterpillars can cause as intense defoliation as the cinnabar moth (Ellis, 1960). May-March.
Pupae In a cocoon on ground debris or in thick vegetation.
Adult May-June, but a small second generation emergence can appear in September.
Thalera fimbrialis Sussex emerald (geometrid moth) RDB1
Larvae Usually on wild carrot (Daucus carota) but feeds on Ragwort as a secondary foodplant.
Adult July - Early August. Occurs only at Dungeness in Kent.
Tyria jacobaeae Cinnabar moth (arctiid moth)
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| Cinnabar moth (Tyria jacobaeae)
© Ian Kimber |
Senecio jacobaea: plus S. erucifolius, S. vulgaris and S. squalidus; also other plants such as Tussilago farfara (presumably when starving). Females appeared to oviposit more on denser stands of Ragwort (Meijden, 1979).
Larvae Gregarious and often strip plants of leaves and flowers. dispersing to find alternative fresh plants. July-august. Populations are notoriously variable from year to year. Parasites can be involved in these fluctuations.
Pupae In soil.
Adult Late May-early July. Easily disturbed by day.
Recognition Easily recognised yellow and black-ringed caterpillars. The adult moth has bold red and grey markings, but the wings are much broader than those of burnet moths.
MICRO MOTHS
Four tortricids, two pyralids and a plume moth are Ragwort specific. Note that the latter appears to be specific to Senecio aquaticus, Marsh Ragwort.
Two pyralid moths have Solidago (Golden-rod) as the main alternative foodplant, but this plant is rare or absent from most districts so Ragwort must generally be the key foodplant.
Cnephasia conspersana Coast shade (tortricid moth)
Polyphagous in composite flowers, including Senecio.
Commophila aeneana Orange conch (tortricid moth) Nationally Scarce B
In root stock of Senecio jacobaea.
Cochylis dubitana Little conch (tortricid moth)
On flowers/seed heads of various composites, including Senecio jacobaea.
Cochylis atricapitana Ragwort crown boring moth (tortricid moth)
First generation in flowers and in flower stalks, second generation in lower stems and roots of Senecio jacobaea.
Epiblema costipunctana Ragwort bell (tortricid moth)
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| Ragwort bell (Epiblema costipunctana)
© Ian Kimber |
Larvae Summer brood in stem, autumn brood in rootstock.
Pupae In a cocoon, in summer sometimes in stem.
Adult May-July, July-August, but in Scotland only a single brood at end May-early July: rests by day on foodplant, flies in late afternoon sunshine.
Summer brood in stem, autumn brood in rootstock of Senecio jacobaea.
Eucosma campoliliana Marbled bell (tortricid moth)
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| Marbled bell (Eucosma campoliliana)
© David Painter |
Larvae in seed heads and sometimes burrowing into stem. Pupa in a cocoon in the soil. Adult June-early August: flies in late evening and night.
Hellinsia osteodactylus Small goldenrod plume moth
Larvae In flowerheads/seedheads of Solidago or Senecio; hibernates full fed among leaf litter.
Pupae On or near foodplant
Adult July, easily disturbed by day though normally flies at dusk and night.
Hellinsia chrysocomae Scarse goldenrod plume moth Nationally Scarce B
Larvae In flowerheads/seedheads of Solidago, Senecio or Aster; hibernates full fed among leaf litter.
Pupae On or near foodplant
Adult July, easily disturbed by day though normally flies at dusk and night.
Homoeosoma nebulella Large clouded knot-horn (pyralid moth) Nationally Scarce B
Larvae Feed in flower-heads eating the flowers and seed heads of Ragwort and Spear Thistle (Tansy and Ox-eye Daisy given in some references).
Pupae In loose blackish cocoon in soil or among debris on ground.
Adults July (rarely also September). Flies at dusk and during the night, visiting Ragwort and thistle flowers.
Homoeosoma nimbella Scarse clouded knot-horn (pyralid moth) RDBK
Larvae Feed in flower-heads eating the flowers and seed heads of Ragwort and some other composites.
Pupa Over winters in a tough cocoon (main catalogue does not state where).
Adult Late May-August: flies at night.
Perinephela lancealis Long winged pearl (pyralid moth)
On leaves, flowers and seed heads of various plants, including Senecio.
Phycitodes saxicola Small clouded knot-horn (pyralid moth)
A coastal species whose biology is poorly defined but Ragwort is the main confirmed foodplant in the UK, the larvae occur in the flowerheads. Adult June-August.
Phycitodes maritima Chalk knot-horn (pyralid moth)
Larvae On Senecio jacobaea and Yarrow (sometimes Tansy). Initially in the stem and leaf axils, later feeding on the flowers in a web, sometimes gregarious.
Pupae In a cocoon on the ground.
Adults May-August, apparently as two broods. Fly at night, visiting Ragwort flowers. Mainly coastal but also occurs in Scottish Highlands.
Platyptilia isodactyla Ragwort plume moth
Eggs on underside of leaf of Senecio aquaticus.
Larvae in stem exuding frass at the axil of a leaf: also in the flower head and on the leaves. Autumn larvae hibernate in the stems.
Pupae In the stem or under a web on the upperside of a leaf of the foodplant or adjacent herbage.
Adults in two broods, June and August-September. Flies at dusk and later sometimes comes to light.
Recognition One of several medium sized plume moths with brown wings bearing dark and white markings near forewing apex.
Scoparia pyralella Meadow grey (pyralid moth)
Larvae On roots of Senecio jacobaea and dead plant material.
Adults June-July, rests on rocks and tree trunks during day.
PLANT BUGS
Aphis jacobaeae (Ragwort aphid)
On Senecio jacobaea. Live in colonies, usually attended by ants. Colonies of aphids may occur girdling the stem. leaf axils of inflorescence; when at the base of the stem, ants may enclose them within an earth tent. Assumed to be widespread on sandy or gravelly soils. [The tibiae are dark]
THRIPS (Thunder bugs)
The list of 23 species found on Ragwort (Harper & Ward, 1957) includes many spurious attributions to Ragwort.
A more recent reference (Mound et.al. 1976) reveals that one species is Ragwort specific, and two others get a particular mention for Ragwort. Yellow composites more generally are utilised by Thrips validus, Aeliothrips intermedius and A. tenuicornis: the later two species are also on yellow legumes and yellow crucifers. Beyond that, there are only a few wider generalists that might use Ragwort. Thus, rather than the 23 species claimed to be Ragwort associated, a more meaningful figure is three in terms of Ragwort being a significant foodplant, especially where the alternatives are not available in sufficient quantity.
Haplothrips senecionis
Associated with Senecio jacobaea and S. aquaticus. Adults May-August.
Widespread in northern Britain but recorded south to Berkshire.
Haplothrips setiger
Associated with Senecio, Crepis, Matricaria and Achillea.
Thrips pillichi
Associated with flowers of composites such as Senecio and Achillea.
MITES
Aceria leioproctus (Ragwort gall mite)
Causes shortening of shoots and deformation of leaves, about ends of shoots, covered in whitish hairs. Senecio jacobaea. South-east England.
BEES
(as flower visitors)
About 30 species of solitary bees make use of Ragwort flowers where available. They can use a selection of alternatives so cannot be regarded as Ragwort dependent. However, if good alternatives of the right sort are not available during a particular part of the season, the presence of Ragwort flowers can be vital to local survival of these bees. In this respect Ragwort is an important plant is the countryside mosaic.
Three species of bee stand out as having an unusually high dependence on Ragwort flowers.
Heriades truncorum (Daisy carpenter bee) RDBK
Daisy carpenter bee (Heriades truncorum) © Bernhard Jacobi
A Red Data Book solitary bee which shows c.85% allegiance to Ragwort flowers.
Stelis breviuscula RDBK
An even rarer bee, which is parasitic on Heriades truncorum; it also has a strong affinity with Ragwort (using the same patches of flowers as the host).
Colletes daviesanus (Davies’s colletes), a common bee, usually found on Ragwort or closely related compositae flowers.
PARASITES
(of Ragwort eating insects)
Knowledge of the insect parasites of the primary Ragwort fauna is very incomplete. Some of these parasites in turn have their own parasites, so the web of life becomes pretty complicated. Most of these species are parasitic wasps but some parasitic flies are also involved.
Old literature names for these insects are difficult to interpret into correct current names so no detailed analysis is offered. In any case, knowledge about host specificity is uneven at best, and often very uncertain.
About 30 species of insect parasites are recorded via very few studies in a few districts. The true figure must be very much higher. Fifty would be a minimum estimate of the numbers of species involved.
INVERTEBRATES ARE FUN - Ideas for study
1. Leaf beetles
These can be found on rosettes of leaves or on flowering plants.
How many species can you find and which are dominant in your area at different times of the year?
Can you identify them with the key?
How much damage do they do to the leaves?
Is there a relationship between the amount of damage and the height of the plant?
Is there more feeding damage on sunlit plants than shaded plants?
2. Nectaring insects
What types of insects visit Ragwort flowers?
Are there more insects on sunlit or shaded Ragwort flowers?
Are there disproportionately more insects on Ragwort flowers which have more individual flowerheads?
What times of day are the most popular for drinking Ragwort nectar?
What times of year are the most popular for drinking Ragwort nectar?
Do different insects visit Ragwort at different times of the day or year?
If different species of Ragwort and groundsel grow nearby, is a difference between insects visiting the two plants?
Compare the insects visiting Ragwort with other yellow flowers or flowers of a different colour.
How far away are the Ragwort plants from the bumblebee nest (follow the bees)?
3. The cinnabar moth
How many caterpillars (distinctively yellow and black-ringed) does it take to ravage Ragwort plants of different sizes?
How far can caterpillars walk in search of fresh plants?
When keeping wild caught caterpillars, what proportion are killed by emerging parasitic grubs?
Keep the cocoon of the grubs - how many types of minute wasps emerge?
What proportion of pupae produce parasitic wasps or flies instead of moths?
CAUTION. Ragwort is distasteful and poisonous to eat (as are various other wild plants). Do not touch Ragwort unless absolutely necessary and if you do make sure you wear washing up gloves. Do not wipe eyes or cuts and do wash your hands before eating. Cinnabar caterpillars absorb the toxins and the pupae and adult moths still contain the distasteful chemicals; they are safe to handle (but not to eat or squash!).
Links
Full text of the Wildlife and Countryside Link position:-
http://www.wcl.org.uk/downloads/2003/Link_ragwort_control_29Sep.pdf
Defra’s Draft Code of Practice to Prevent and Control the Spread of Ragwort
http://www.defra.gov.uk/farm/wildlife/weeds/pdf/cop_ragwort.pdf
Full text of the 17 October House of Lords debate at:-
http://www.publications.parliament.uk/pa/ld200203/ldhansrd/vo031017/text/31017-04.htm#31017-04_head0
Full text of the 12 November House of Lords debate at:-
http://www.publications.parliament.uk/pa/ld200203/ldhansrd/vo031112/text/31112-33.htm#column_1510
The British Horse Society position can be seen at:-
http://www.bhs.org.uk/DocFrame/DocView.asp?id=1089v
REFERENCES
This list is selective.
Cameron, E. 1935. A study of the natural control of Ragwort (Senecio jacobaea L.). Journal of Ecology 23: 265-322. [includes faunal lists]
Chinery, M. 1998. A field guide to the insects of Britain and Northern Europe. Collins, London. [recognition of types of insects]
Crawley, M.J. & Gilliman, M.P 1989. Population dynamics of cinnabar moth and Ragwort in grassland. Journal of Animal Ecology 58: 1035-1050.
Dempster, J.P. 1971. The population ecology of the cinnabar moth Tyria jacobaeae L. (Lepidoptera, Arctiidae). Oecologia 7: 26-67.
Dempster, J.P. 1982. The ecology of the cinnabar moth Tyria jacobaeae L. (Lepidoptera, Arctiidae). Advances in Ecological Research 12: 1-36.
Ellis, E.A. 1960. The insects. In Steers, J.A. (Ed.) Scolt Head Island. (Revised Ed.). Heffer, Cambridge. [referred to under cinnabar moth]
Falk, S. 1991. A review of the scarce and threatened bees, wasps and ants of Great Britain. Research and Survey in Nature Conservation, No. 35. Nature Conservancy Council, Peterborough.
Emmett, A.M. 1988. A field guide to the smaller British Lepidoptera. 2nd Edition. British Entomological & Natural History Society. [Title deceptive. A catalogue of micromoths with condensed details of their life history, including foodplants]
Goater, B. 1986. British Pyralid moths: a guide to their identification. Harley Books, Colchester.
Harper, J.L. & Wood, W.A. 1957. Biological Flora of the British Isles: Senecio jacobaea L.. Journal of Ecology 45: 617-637. [includes faunal lists]
Harris, P., Thompson, L.S., Wilkinson, A.T.S. & Neary, M.E. 1978. Reproductive biology of tansy Ragwort, climate and biological control by the cinnabar moth in Canada. Proceedings of 4th International Symposium on biological control of weeds. pp. 163-173. (Senecio jacobaea)
Heath, J. (Ed.) 1979. The moths and butterflies of Great Britain and Ireland. Sphingidae - Noctuidae (Part I). 9. Harley, Colchester.
Heath, J. (Ed.) 1983. The moths and butterflies of Great Britain and Ireland. Noctuidae (Part II) and Agaristidae. 10. Harley, Colchester.
HL Hansard, 17 October 2003, 653, cols. 1234-1248. [House of Lords debate: Ragwort Control Bill (Second reading)]
Hyman, P.S. & Parsons, M.S. 1992. A review of the scarce and threatened Coleoptera of Great Britain, Part 1. UK Nature Conservation No. 3. Joint Committee for Nature Conservation, Peterborough.
Kevan, D.K. 1967. The beetle species of the genus Longitarsis Latreille (Col., Chrysomelidae). Entomologists' Monthly Magazine 103: 83-110.
McEvoy, P.B. 1984. Seedling dispersion and persistence of Ragwort Senecio jacobaea (Compositae) in a grassland dominated by perennial species. Oikos: 42:138-143.
Meijden, van der E. 1979. Herbivore exploitation of a fugitive plant species: Local survival and extinction of the cinnabar moth and Ragwort in a heterogeneous environment. Oecologia (Berlin) 42: 307-323.
Mound, L.A., Morison, G.D., Pitkin, B.R. & Palmer, J.M. 1976. Thysanoptera. Handbooks for the Identification of British Insects 11. [Thrips]
Owen, D.F. 1952. City bombed sites survey: The Lepidoptera of Cripplegate. London Naturalist 1951: 84-88.
Redfern. M and Shirley, M. 2002. British Plant Galls: identification of galls on plants and fungi. Field Studies 10: 207-531. [Aidgap key available from Field Studies Council].
Skinner, B. 1998. Colour identification guide to moths of the British Isle. (2nd Ed.). Viking. (Penguin Books), Middlesex.
Southwood, T.R.E & Leston, D. 1959. Land and water bugs of the British Isles. Warne, London.
Stubbs, A.E. 2002. British Hoverflies; an illustrated identification guide. British Entomological & Natural History Society, Reading. [useful for flower visitors. See this society's website]
Sutcliffe, J. 2003. Common ragwort Senecio jacobaea: Towards a conservation strategy. Information Note. English Nature, Peterborough. [see English Nature website, under publications]
West, B.K. 1986. Some aspects of the natural history of the ruby tiger moth, Phragmatobia fuliginosa L. (Lep.: Arctiidae). Entomologists' Record and Journal of Variation 98: 129-134.
West Sussex County Council 2003. County Council will mount sustained campaign to tackle the menace of Ragwort: News Release, February 27th 2003. West Sussex County Council.
White, I.M. 1988. Tephritid flies. Diptera Tephritidae. Handbooks for the Identification of British Insects 10 (1).
Windig, J.J. 1993. Intensity of Longitarsus jacobaeae herbivory and mortality of Senecio jacobaea. Journal of Applied Ecology 30: 179-186. {Netherlands, on dunes]
Wolferstan, F. 2003. Letter. The Sunday Telegraph (3 August 2003).
Yarrow, I.H.H. 1986. Flight table. In Betts, C, (Ed.). The Hymenopterists Handbook (2nd Ed.). The Amateur Entomologist 7. [Published by the Amateur Entomologists' Society]
