Tag Archives: invasives

Invasive species have cost UK at least £5bn since 1970s, study reveals

Photo by Denis Fournier under Creative commons

The Guardian reports ecosystem-altering plants and animals that wipe out native wildlife, often introduced by humans, have cost the country at least £122m a year on average since 1976, causing structural damage to buildings, clogging waterways and ruining crops. These include the grey squirrel, Japanese knotweed and the European rabbit. 

Raccoon dogs may be Britain’s next non-native pest, study finds

Raccoon dog photo by Tambako The Jaguar under creative commons

The Guardian reports they are cute and furry, and could become the UK’s next major non-native pest. Raccoon dogs, an exotic member of the fox family that is native to Japan, China and Siberia, are one of the most destructive invasive species at risk of becoming established in Britain, experts say.

A “horizon scanning” study funded by the Department of Environment, Food and Rural Affairs identified the raccoon dog and the raccoon as the only mammals on a list of 20 invasive species likely to reach UK shores and destroy native wildlife or bring disease. 

Government agrees to release parasite wasps to kill invasive pests attacking sweet chestnut trees

iNEWS reports thousands of parasite wasps are set to be released in England in an effort to kill an in invasive pest attacking sweet chestnut trees. The Government has granted approval for Torymus sinensis, a type of parasite wasp, to be introduced in order to attack the invasive Oriental Chestnut Gall Wasp.

Concern has been mounting about the fate of England’s sweet chestnut trees after the Oriental Chestnut Gall Wasp was first spotted in Kent in 2015. The wasp’s larvae causes abnormal growths – known as ‘galls’ – on the leaves of sweet chestnut trees. Large infestations can weaken the host tree, making it more vulnerable to pests and diseases.

Box-tree moth, Agapanthus gall midge and Gypsy moth arrive in Normandy – Gardeners Beware!

Species that have been introduced into areas outside their natural range through human actions and that pose a threat to native wildlife, are known as invasive non-native species.  Sadly some have made their way to Normandy, affecting our native wildlife.  However, you can help, by recognising them and reporting them, and even taking measures to control them. Read these details, from FNW Committee member, Bill Stanworth, on three such species to look out for.

The box-tree moth (Cydalima perspectalis) has been recorded for the first time in Normandy at Springhill garden. Adult moths were attracted to a mercury vapour lamp in July 2020 and later in the year larvae were found on its foodplant, box (Buxus sempervirens) growing in the same garden. The moth is a native of the Far East and so its arrival in Europe (in 2006) is thought to have been from imported box plants – ugh.

The first record of the moth in the U.K. was from Kent in 2007 but a year later it was found in Weybridge, Surrey. Since then the moth has been gradually increasing and from distribution maps the moth may have been in our area for a year or so. Papers about the moth and its distribution can be found on the RHS website.

The adult moth, shown below is large and very distinctive. Its markings are variable and even a brown form exists. The stripy green caterpillar is also quite distinctive and is shown resting below on its foodplant. It creates silk strands that tie leaves together forming a lair from which it can feed and retreat into, in times of danger.

Box-tree moth
Box-tree moth catepillar

You can see from the photos below that even in less than one season they can seriously damage the plant. Feeding signs and frass are shown on the left and serious defoliation on the right. If you see this happening to your box bushes please check with the RHS and other websites for control methods (preferably using the non-pesticide methods).

We urge you to control this species as box is a native plant in southern England and it could have a serious effect on our best-known native boxwood at Box Hill, Surrey and other sites in the county and country. If you see the box-tree moth the RHS would like to know, you can submit your records on their website via their box-tree moth survey.

Box bush damage
Box bush damage

The second pest to look out for is the Agapanthus gall midge, which was also found in Springhill garden for the first time in 2020. It’s another devastating pest (if you grow Agapanthus in your garden!), a fly this time, that lays its eggs on the young Agapanthus flower buds. The tiny, creamy-yellow larvae develop and cause the flower bud to become distorted, go brownish and most fail to open. A photograph of the affected buds (here detached from the plants) is shown below.

According to the RHS the midge causing this was new to science and only discovered in 2014, this time at Wisley but it is probably a native of southern Africa, home of the plants. Control methods are given on the RHS website. Agapanthus flowers are popular with some native pollinators; an example shown here is probably a melanistic garden bumblebee (Bombus hortorum) from Springhill garden. This one spent a lot of time on this white flowered variety! Sadly many Agapanthus flowers at Springhill were ruined this year.

The RHS are asking for help from gardeners who have seen agapanthus gall midge or damaged flowers and request you send photos of symptoms on the flowers and buds, plus opened buds showing larvae where possible, to entomology@rhs.org.uk on their website.

Agapanthus flower buds
Bumble bee on Agapanthus flower

Another invader and potential pest is the gypsy moth (Lymantria dispar). The male shown below was attracted to a mercury vapour lamp at Springhill garden on 7 August 2020. On mainland Europe the moth can be a serious pest, stripping broadleaved trees (particularly apple, plum and willows; oaks and poplars in forests) and bushes.

Look out for patches of eggs covered with yellow/brown hairs on trunks and walls over winter or for large dark grey/black hairy caterpillers with reddish spots from April to June/July. Apparently the hairs don’t cause irritation of the skin unlike the oak processionary moth. The RHS website says ‘whilst a single defoliation from this caterpillar even early in the season, should not affect the vigour of a host plant, repeated defoliations can have an adverse effect’ and advice is given with regards control. They also very sensibly say ‘where possible tolerate populations of caterpillars’.

This moth (not mentioned/recorded in ‘The Larger Moths of Surrey’ [Graham A. Collins] published by SWT in 1997) was a former resident in the East Anglian fens but it lived on bog-myrtle and creeping willow and so wasn’t considered a pest. The European strain was accidentally introduced and has spread rapidly in the London area. Hopefully, as the large bodied females are mostly flightless, we won’t be troubled for a while.

There is no statutory requirement to notify sightings of gypsy moth to the plant health authorities but you can report serious damage to the government’s ‘Forest Research’ website: TreeAlert (their on-line pest reporting tool).

Gypsy moth

2018 saw the first arrival of the oak processionary moth (Thaumetopoea processionea) to Normandy (see our previous article). No moths were seen in Normandy in 2019 as far as we know but you may have seen that the Forestry Commission have erected posters warning the public to be alert for them and report them when seen. In addition at least one team has been seen on Normandy Common searching for evidence of their presence. This year three males were attracted to the mercury vapour lamp at Springhill so please stay vigilant.

UK scientists confirm arrival of brown marmorated stink bugs

Brown marmorated stink bug photo under creative commons

The Guardian, and iNEWS report it is brown, stinky and will strike fear into the hearts of apple and other fruit growers. Scientists have now confirmed that the brown marmorated stink bug (Halyomorpha halys), a small flying insect that emits an unpleasant almond-like odour, has arrived in Britain, after most probably hitching a ride on packaging crates. 

Killer pigmyweed from New Zealand putting Britain’s lakes at risk

Sky News reports pigmyweed was first sold in the UK as an ornamental plant for domestic ponds but it was banned after damaging rivers and lakes. The New Zealand pigmyweed has already wiped out several native plant species in the Lake District and there are fears that the area’s most pristine lakes are next. 

The Telegraph and The Express report staycationers taking a holiday in the Lake District have been warned they could be spreading a killer weed from New Zealand, which is at risk of smothering the aquatic life in the famous lakes. Pigmyweed, once sold as a decorative plant for home ponds,  is already responsible for several native plant species being wiped out in the Lake District, and there are fears that the area’s most beautiful lakes could be infested next… if people travel from an infested lake to a pristine one without taking care to wash any plant debris off their clothes, dogs, boats and bodies, they risk spreading the killer weed. 

Nature defence force to fight off invasive species

The Times reports a citizens’ army to protect British wildlife and slow the arrival of invasive species like Japanese knotweed is being considered by the government. Such invaders cost the UK economy £1.8 billion a year, according to the Commons environmental audit committee, by damaging biodiversity and transmitting disease. Its members have called for a group of over a million volunteers to be set up to tackle the spread of the harmful species, which also include Himalayan balsam and Australian swamp stonecrop.This would follow the example of New Zealand, which hopes to recruit 150,000 volunteers by 2025 to help monitor and destroy invasive species. 

Deadly fungus spread by trade in amphibians ‘could wipe out British newts’

A deadly “salamander-eating” fungus that is already causing havoc for European amphibians is rife in the pet trade, prompting fears it could spread to the UK’s vulnerable newts, report the Independent.

In a study partly funded by the British government, scientists found that seven of the 11 private amphibian collections tested from Western Europe were positive for the “Bsal” infection.

The disease is caused by Batrachochytrium salamandrivorans, a fungus that has spread like wildfire from Asia and killed 99 per cent of fire salamanders in the Netherlands.

Experts are concerned some of the UK’s newts, which are already teetering on the edge of extinction thanks to habitat loss and intensive farming, could be the next victims of this plague.

PEST! Oak Processionary moth (OPM) has arrived in Normandy

This moth was trapped in a Normandy garden in early August this year. It has been reported to the Forestry Commission who says that their nests have been found in the Pirbright area. OPM are a pest species in Europe and also a health hazard.  Additional information on the moth is given below. If you find caterpillers or nests please don’t disturb them but report to the Forestry Commission as directed below, to the land owner (see below) and or to us.  

Selected OPM information from the Forestry Commission’s website: 

OPM (Oak Processionary Moth) was accidentally introduced from continental Europe into London in 2005 and, despite eradication attempts, it has become established and the area affected has grown. (Normandy is currently outside the 2018 Core zone for OPM and in the Control or buffer zone.) Nevertheless, OPM cannot be left uncontrolled, and the main focus of control now is to prevent or limit further outward spread of the pest. This requires action by everyone who owns or manages oak trees in the affected areas. 

Contact with the hairs can cause itching skin rashes and, less commonly, sore throats, breathing difficulties and eye problems. This can happen if people or animals touch caterpillars or their nests, or if the hairs are blown into contact by the wind. The greatest risk period is May to July, but they can be present on old nests, and could be blown or touched at any time of year. Detection of adult males, which are strong flyers and can travel several kilometres from the nest from which they emerged, does not necessarily mean that the infestation has spread and a new breeding population is being established. By contrast, the female is not a strong flyer, and is rarely found more than about 500 metres from her original nest. However, carrying out visual surveys for egg masses over the following winter, and for larvae the next spring, is recommended in areas where males are trapped. All oak trees within 200 metres of where OPM is trapped should be inspected as soon as possible in case there are nests present. A second inspection later in the year is also considered wise. 

Oak Processionary Moth (Thaumetopoea processionea) caterpillars are covered with thousands of minute, irritating hairs which can be released as a defence mechanism or blown off by the wind. The larvae develop tiny, irritating hairs from their third (L3) stage onwards to pupation. A single, fully grown larva can carry thousands of hairs. These hairs, which are barbed, contain an irritating substance called thaumetopoein, from which the species gets part of its scientific name, Thaumetopoea processionea. 

The caterpillars build communal nests on the trunks and branches of oak trees to protect themselves from predators. Once released, the hairs can persist in the nests and the environment for a long time, posing a long-term nuisance to people and animals, such as horses and dogs, unfortunate enough to come into contact with them. 

Advice on Guildford Borough Council’s website: 

What to do if you see OPM 

If you see any OPM nests or caterpillars, do not touch or approach them. The caterpillars have a distinctive habit of moving about in or under oak trees in nose-to-tail processions, which gives them their name. 

The silken webbing nests are white when new, and often have silken trails leading to them. They quickly become discoloured and harder to see against the dark colour of oak tree bark. 

The main risk period is April to July, when the caterpillars are active. However, avoid nests, even ‘spent’ nests, at any time, because the hairs in them can remain irritating for many months. Nests can sometimes fall to the ground. 

Report them immediately to the Forestry Commission, which is leading efforts to control its population, spread and impacts. 

How to report OPM 

Please report sightings on Guildford Borough Council owned land to Parks & Leisure Services by emailing parks@guildford.gov.uk or phoning 01483 444 718. 

Please report sightings on other land in the borough to the Forestry Commission using their Tree Alert online pest reporting form, which you can access at the Forestry Commission website. You will have to add a photograph to your report, but do not risk contact to get a photograph. 

It would be courteous to contact the landowner if you know who they are. 

If you cannot use Tree Alert or get a photograph, you may report them by email to opm@forestry.gsi.gov.uk or by phoning 0300 067 4442.