Why all the fuss about Invasive Species?
It seems that you can't open a paper or journal recently without reading doom and gloom stories about our country being taken over by invasive Species. Are we safe from attack, is it a case of unnecessary concern, or should we really keep looking over our shoulders expecting to be attacked from all angles?
To look at the species that effect us in the sports turf industry, we can all but rule out anything that walks or crawls. There are a number of plants and just one insect: Japanese Knotweed (Fallopia japonica), Giant Hogweed (Hearcleum mantegazzianum), Himalayan Balsam (Impatiens glandulifera), Ragwort (Senecia jacobea) and the Brown Tailed Moth (Euproctis chrysorrhoea).
This year the Environment Agency published a list of the top 10 invasive species. Japanese Knotweed is the most wanted, Giant Hogweed at number 4, Himalayan Balsam at number 6. There is no mention of Ragwort or the Brown Tailed Moth. but, in our industry, they come into the same category of invasive species. Strictly speaking Ragwort is not an alien invader, being native to our shores, but problematic and invasive none the less.
So what are the problems caused by these species?
I would like to start with three examples and, in the next article, look at the ones gaining the majority of the press at the moment Brown Tailed Moths (Euproctis chrysorrhoea)
Brown Tailed Moths are seemingly becoming more and more widespread in the UK. Perhaps a sign of Global Warming, they seem to be spreading Northward, creating destruction and havoc along the way. Brown Tailed Moths have a particular liking for causing defoliation of forests, hedgerows, orchards and flowering shrubs.
The sting in the tail comes from the hairs on the caterpillar that can cause sever dermatitis and breathing difficulties when in contact with humans, dogs and cats. This can lead to severe discomfort and need not even be through direct contact. The hairs from the caterpillar can be wind borne and can even contaminate washing left out on the line to dry, causing pain and discomfort to the unsuspecting wearer of the these clothes.
How to control Brown Tailed Moths?
Biological control of the Moths themselves is having some success. Exosect (www.exosect.com) produce biological trapping, monitoring and control products, to control the moths and limit their ability to breed. However, it is more common to deal with the caterpillars as they are more easily identified and it is they that cause the damage.
During the autumn and winter months the caterpillar larvae hibernate and develop in 'tents' attached to branches of trees and shrubs. Vegetation containing these tents should be cut and immediately burnt. Each tent contains up to 300 larvae that, once the weather warms, will spread throughout the host plant causing total defoliation and offering the potential for serious health issues to the public in the vicinity.
Operatives working around these infestations must be made aware of the hazards involved and only those with suitable training and the correct PPE should attempt any form of control.
Himalayan Balsam (Impatiens gladulifera)
Himalayan Balsam is the UK's largest growing annual plant, reaching heights of up to 3m in a matter of weeks. With an attractive flower and an interesting method of seed disposal, the invasive qualities of this plant are often underestimated. It is not poisonous, nor will it cause structural damage, however, its ability to spread and form ecologically barren monocultures must not be ignored.
Originally imported for its truly desirable flowers and attractive appearance, it has, like so many similar imports, found life in the UK relatively easy and has therefore become more and more widespread.
Traditionally found along river banks due to the ease of spread that exploding seed heads and water transport offer, Himalayan Balsam is now spreading inland and is becoming a common site in highway and rail corridors.
Forming large riparian single species infestations, river banks become unstable and liable to erosion once the vegetation has died back and during periods of high water flow in autumn and winter months. The dead vegetation washed into the rivers also causes flooding by blocking outlets and restricting flows.
Control should be undertaken throughout the growing season by strimming and spraying using either Glyphosate or 2-4,D Amine. Treatments should be undertaken for up to 3 years and care taken so as to allow for the regeneration of native flora and the exhaustion of the seed bank, all of which helps to prevent future infestations. 2,4-D
Amine is a selective herbicide suitable for use on or adjacent to watercourses. Being selective, it allows for the re-growth of grasses and the like. Glyphosate is a total weedkiller and will, therefore, kill all grass and prevent re-naturalisation, so use should be accurate and targeted. As with all applications of herbicides on or adjacent to watercourse, the Environment Agency must be contacted and relevant permissions granted thereafter.
This plant is spreading at an alarming rate through the country and control methods should be thorough and consistent at all times.
Ragwort (Senecio jacobea)
Ragwort has become a common sight on most of our highway corridors throughout the country, as well as on agricultural set aside fields, railway and river embankments; in fact any where that has poor maintenance regimes. This yellow flowering plant strikes the fear of god into horse owners everywhere, to the point where it has its own governmental act.
The plant is not, as some would think, an alien invader that is spreading everywhere; it is in fact a native plant that has a very important part to play in the ecology and life cycle of numerous organisms. There are approximately 200 species of insects and the like that use Ragwort as a major food source.
Indeed it is true that it can kill horses by causing irreparable liver damage when digested over many years but, to focus on that is to over look a plant that is environmentally important and should not be eradicated. Controlled, yes, but not eradicated.
As with all seed bearing plants, its spread along corridors is a large factor in its prevalence on road side verges. The Highways Agency generally take this very seriously and spend millions of pounds every year to try and quash the public outrage at seeing this flower on the verges. Highways Agencies and Local Authorities often receive severe criticism and are held up as the reasons for the widespread infestations of Ragwort, adjacent landowners blaming anyone possible to defer liability from themselves and to try and improve the safety of their land.
Horses, as a rule, will not eat live Ragwort, the taste is not to their liking. However, once cut and the toxins within the plant become more palatable as they break down, horses actually find it irresistible. This is why any hay cutting or control methods must be undertaken with care and caution.
Once the animals have eaten enough Ragwort they will die. There is no cure.
Estimates of fatalities through Ragwort poisoning range from 10 to 6500 per year in the UK alone. This is a much talked about plant that has myths and legends dating back to the days of the Pharaohs if everything is to be believed. Whatever the actual figure for fatalities, it is indeed a plant that needs controlling in certain situations, and it definitely does not need encouraging.
Basically a biennial plant, in the first year it forms a ground covering rosette and, in the second year, produces seed heads with up to 200,000 seeds per plant. Each of these seeds may lay dormant for 20 years or more, so control is a management issue that needs to be undertaken with a long term approach.
The traditional method of 'Hand Pulling' is perhaps one of the reasons why it has spread so far and seems impossible to control. This method not only puts the operator at risk of severe personal injury from the toxins within the plant but, by the very nature of pulling, it will cause the spread of the plant.
Ragwort can regenerate from tiny root sections left in the ground, the seeds present in the sward from previous years will be encouraged to grow as the ground is disturbed by the pulling operation and there is also the chance that by pulling the plant one will dislodge the Ragwort seeds and allow all of the seeds to be spread within the area of works.
I was recently horrified to hear the British Horse Society arranging Ragwort Pulling Parties during September when the plant has finished flowering and the seeds are just right for being easily spread. This method of control will not work.
So what are the options left open to us to control Ragwort in our parks, open spaces and road verges? There are two methods that seem to be relatively successful. One of which is the application of herbicides such as Glyphosate or Barrier H sprayed specifically to the plants whether in rosette stage or during the flower stage. Ideally this should be carried out during periods of active plant growth - April onwards until the plant is in flower.
Mowing can be effective as the plant will be forced into becoming a perennial Rosette and therefore will loose the ability to produce seed heads and then propagate. It will take many many years of close mowing to enforce thorough control, but it is a method of control not involving use of herbicides.
Whatever method is utilised it will only be fully effective if the management of the grass areas is of a high standard. Pasture Management techniques, which can be used across the board, include reducing compaction and improving drainage as well as encouraging dense native sward establishment thereby out-competing the Ragwort.
For further information on the invasive weeds described above as well as cutting edge research papers on a wide range of invasive issues please visit the web site www.t-c-m-rd.co.uk where information and advice is freely available. tcm (r&d) Ltd has been established to progress research into providing science based, practical, innovative solutions to vegetation management and invasive weed issues.