Ragwort

Introduction

Senecio jacobaea, L.

The Weeds Act of 1959 provides for orders for the control of Common Ragwort, this was updated by the Ragwort Control Act of 2003. The act states:

1. Where the minister of Agriculture fish and food (in this act referred to as 'the Minister') is satisfied that there are injurious weeds to which this act applies growing upon any land he may serve upon the occupier of the land a notice, to take such action as may be necessary to prevent the weeds from spreading.
2. This act applies to the following injurious weeds, that is to say:
• Spear Thistle
• Creeping or Field Thistle
• Broad-leaved Dock
• Common Ragwort

Therefore, it is incumbent upon landowners to know how best to control Common Ragwort.

Description

Common Ragwort is a biennial member of the Asteraceae family. Coincidentally both of the thistles which form part of the list of injurious weeds are also members of the Asteraceae family. Many species within this family have the ability to produce large numbers of seeds, and frequently they equip them with their own transport system i.e. a feathery pappus familiarly known as thistle-down: the "clock" of a Dandelion clock. Common Ragwort is widespread throughout the UK and can be found on wasteland, development land, roadside verges, railway land, amenity land, conservation areas, set-aside, woodland and grazing land commonly flowering in August. The tall nodding heads of yellow flowers are composed of yellow disc and ray flowers which support over thirty species of invertebrates, some totally dependent on Common Ragwort as a food source.

Common Ragwort is an erect plant usually 30-100cm high, stems are tough and often tinged red/purple near the base. Ragwort is normally a biennial producing a rosette of basal leaves in the first year followed by flower stems in the second year. Flowering is between June and October after which the plant dies. However, if it is cut down to the ground during the second year it can continue to regrow in a third year utilizing energy resources in its deep tap root.

Common Ragwort contains pyrrolizidine alkaloids which is poisonous to most invertebrates although some such as the Cinnabar Moth use this trait to their advantage. The Cinnabar Moth, Tyria jacobaeae, is a brightly coloured moth that flies during the day. As a result of this it is often mistaken for a butterfly. It gets its name from the red mineral cinnabar. The caterpillars of the Cinnabar Moth are very distinctive. They are striped black and orange/yellow, rather as though they are wearing a football jersey. They absorb the bitter tasting alkaloids that make ragwort distasteful to animals and become distasteful to birds as a result. The bright colours are a warning to birds not to eat them. Inside the plants the poisons occur in a non-toxic form, but after the plant has been eaten it is first changed by the intestines and then broken down by the liver. The breakdown products formed in the liver are toxic but contrary to common belief the alkaloids are excreted within one or two days. Common Ragwort can be a problem for livestock particularly horses. UK government figures for 2005 show a total number of 13 deaths and further figures from the same laboratories in the same source list 10 deaths between 2005 and 2010. One set of figures from a UK Government study for a period in the 1980s and 1990s in cattle shows figures in the 10-20 or to deaths a year range. Whilst the plant is growing, livestock will graze around it however they are unable to detect it once it has been dried in hay or preserved in silage and this is when most incidences of poisoning occur. Palatability of the weed increases when plants are conserved in hay or silage or treated with herbicide.

Methods Of Control

Cultural Methods

Although a prolific seed producer, frequently 20,000 seeds per plant are produced, Common Ragwort seed requires microsites that are free from competing vegetation to germinate and establish successfully. This type of habitat is commonly produced by overgrazing from sheep, horses and rabbits. The most effective method of cultural control is to fence against rabbits, keep the sward full to reduce potential microsites by reducing the grazing pressure if necessary. Good pasture management which keeps the grass sward tight will minimise the chance of ragwort establishing.

Pulling the plant once it is flowering is common practice although care should be taken to ensure the whole root is removed to prevent the weed re-establishing, a Rag-fork can be used. Often this process must be repeated a number of times to remove all signs of roots.

Cutting on a regular basis is also an option. Continue to cut down the vegetation back to ground level and keep cutting it to prevent the weed from flowering, thus controlling its spread from seed.

Cutting and stem removal at the early flowering stage reduces seed production but does not destroy the plant. Cut plants left lying in the field are a serious risk to grazing animals and may still set seed. These should be removed and burned.

A combination of fencing to reduce suitable areas where ragwort can become established, cutting to prevent the plant from seeding and herbicide is probably the most effective. It is important to remove or burn all collected vegetation.

Biological Methods

There is evidence to suggest that T. Jacobaeae, cinnabar moth and L. jacobaeae ragwort flea-beetle can be used as a suitable biological control.

Chemical Methods

Professional Pesticides

Treatment with selective herbicides is most effective when applied to the plant rosettes between late April – early June when the plant is actively growing but before flowering.

Depitox 500 containing 2,4-D as the diethanolamine salt is the main chemical that is used for controlling Common Ragwort when the plant is in the rosette stage. Other combinations of herbicides such as dicamba and MCPA are effective too but again only when the plant is in the rosette stage.

Common Ragwort is also susceptible to the systemic herbicide triclopyr. Triclopyr is the active ingredient in Icade. This selective herbicide is particularly effective at controlling woody weeds such as Brambles, Buddleia, Rhododendron, Sycamore and Ash trees as well as difficult-to-control weeds such as Giant Hogweed and Japanese Knotweed. The benefit of spraying with a selective herbicide is that grasses that are present will not be affected and can happily recolonise the area occupied by the Common Ragwort once it has died.

Domestic Weed Killer

There are currently no herbicides for treatment of ragwort that do not require the person applying the herbicide to be in possession of a valid pesticide application licence. Cultural management is the only option available.