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This virtual collection contains 29 papers on the management of invasive plants.
Perennial plant recovery after the removal of invasive Pinus halepensis in coastal habitats in Cádiz, southern Spain
García-de-Lomas J., Rendón J.L., Pacheco M.J., Riches Z.O.V. & López J.M. (2023), 20, 47-54
Aleppo pine Pinus halepensis is a tree native to the Mediterranean basin. Even within its native range, P. halepensis may behave as an invasive species when planted beyond the original forest areas. Despite its potentially negative effects on the receiving ecosystems, little is known about the response of native plant communities following removal of P. halepensis. In southern Spain, P. halepensis plantings are outcompeting native shrubland communities (Juniperus spp.), which are home to several endangered and protected species. We present the results of an intervention to control the spread of P. halepensis in an area of coastal dunes at the La Breña y Marismas del Barbate Natural Park, Cádiz, southern Spain in 2016. An area of 22.4 ha of P. haplensis cover was removed using portable chainsaws and a forwarder. We analysed the species richness and composition of native perennial plant species recorded three and six years after the removal of P. halepensis in treated, invaded and uninvaded areas. Removal of P. halepensis increased the cover of perennial grasses and woody shrubs typical of sun-exposed areas, such as esparto grass Stipa tenacissima, rosemary Rosmarinus officinalis, turbith Globularia alypum, white-leaved rock-rose Cistus albidus and the shrub Anthyllis citisoides. We conclude that P. halepensis removal promotes coastal shrub recovery. We recommend periodic rounds of manual, selective control every three to five years to avoid reinvasion.
Chemical control of the invasive non-native shrub murtilla Ugni molinae in mountain scrub on Robinson Crusoe Island, Juan Fernandez Archipelago, Chile
Gutiérrez-Guzmán H., Ziller S.R. & Dechoum M. de S. (2019), 16, 27-32
The Juan Fernandez Archipelago is a global biodiversity hotspot, where 67% of plant species are endemic, but competition with invasive plants threatens many native plant species with extinction. Murtilla Ugni molinae is a prevalent invasive plant in the archipelago which displaces native vegetation. This study aimed to determine an efficient one-time control method for murtilla that required little or no follow-up. We used an adaptive management framework to conduct chemical control trials of murtilla in order to identify an effective treatment. Eight different combinations of chemical treatments and manual cutting were tested in four trials between 2015 and 2017. The herbicides Rango (glyphosate) and Garlon 4 (triclopyr) were tested along with a surfactant, an emulsifier, ammonium sulphate and urea. Cutting stems at the base followed by stump application of triplocyr proved ineffective. All other treatments used foliar spraying. The most effective treatment was a foliar application of 3% triclopyr, 2% glyphosate and 15g/l of urea diluted in water, which completely eliminated murtilla in 12 months. This treatment can be used for the control of murtilla over large areas and may also be useful to control other invasive shrubs that have leaves with thick cuticles resistant to herbicide absorption.
Mechanical and manual control of prickly pear Opuntia dillenii in lakeside dunes at Laguna del Portil, southern Spain
García-de-Lomas J., Martín I., Saavedra C., Fernández-Carrillo L., Martínez E. & Rodríguez C. (2018), 15, 32-36
We present the results of an intervention to control prickly pear Opuntia dillenii in an area of coastal dunes with Juniperus spp. and Pinus pinea at the ‘Laguna del Portil’ Site of Community Importance, Huelva, southern Spain, in 2015-2017. In the first stage, a total of 2,266 m³ (approximately 460 MT) of the cactus was removed using heavy machinery, which was supplemented by the manual removal of 4 MT of fragments. Subsequently, as part of the periodic control and monitoring work, a total of 200 and 126 kg of shoots and saplings were removed manually after 15 and 25 months respectively. Twenty-six months after the mechanical removal, the composition of native plant species in treated and reference plots (uninvaded areas that represent well-preserved native vegetation) provided evidence of natural recovery. The economic efficiency of the different control stages was compared. The results suggest that combining mechanical and manual methods, adapted to the abundance, size and distribution of the invasive plant, was an effective approach. Additionally, subsequent annual rounds of control appear to be sufficient to provide effective ongoing control of the invasion of Opuntia dillenii.
Native plant recovery after the mechanical removal of invasive Agave spp. in coastal habitat in Almería, southeast Spain
García-de-Lomas J., Schwarzer H., Sanz F.J. & Fernández-Carrillo L. (2018), 15, 48-49
One year after mechanical removal of invasive Agave spp. in coastal sandy habitats in southeast Spain, the native plant composition showed partial recovery. However, the subsequent proliferation of Agave rhizome offshoots will require periodic rounds of manual, selective control.
Control and eradication of Australian swamp stonecrop Crassula helmsii using herbicide and burial at two ponds at Mile Cross Marsh, Norfolk, England
Sims P.F. & Sims L.J. (2016), 13, 39-41
Crassula helmsii (Australian swamp stonecrop or New Zealand pygmyweed) was first recorded growing on Mile Cross Marsh in Norwich, Norfolk, UK before 2003. Previous management undertaken to prevent the spread of this plant across the site had been unsuccessful. A three-phase project was undertaken in 2012 to control C. helmsii on Mile Cross Marsh. The aim was to eradicate C. helmsii from two infected ponds and reduce the risk of plants spreading through the boundary onto Sweetbriar Marsh Site of Special Scientific Interest. The control programme included herbicide application and in situ burial due to the high level of pond infestation. The project successfully achieved its aim of eradicating C. helmsii from the infected ponds and preventing the further spread of C. helmsii on Mile Cross Marsh. However additional work will be required to fully eradicate the plant from the site.
Feasibility of using glyphosate to control beach evening primrose Oenothera drummondii in heavily invaded coastal dunes, Odiel Marshes, Spain
García-de-Lomas J., Fernández-Carrillo L., Saavedra C., Dana E.D., Rodríguez C. & Martínez E. (2016), 13, 72-78
Beach evening primrose Oenothera drummondii is a perennial plant native to the southern USA and adjacent parts of Mexico that invades coastal habitats in several countries. There are currently no accepted control methods. We conducted a seven-month controlled field trial using the glyphosate herbicide Roundup® Ultra Plus in the Odiel Marsh Nature Reserve, Huelva Province, southern Spain. Different herbicide concentrations were tested by knapsack spraying. We estimated the costs of treating an entire invaded nature reserve in southern Spain where O. drummondii has invaded 123 ha of land. A dose of 20 g active ingredient/litre was the minimum effective dose for this species in coastal dunes. As new seedlings appeared after a single herbicide treatment, periodic treatments would be necessary to maintain the population level below an impact threshold. However, the total glyphosate input (710 kg active ingredient/year) to the Reserve for an indefinite period may give rise to social rejection, and demands for the assessment of ecotoxicological impact on native fauna, adjacent habitats and site uses before initiating control actions at full scale. The control costs of the entire 123 ha invaded area for two herbicide applications/year were estimated at €162,000/year (€1,317/ha/year). This includes materials (30% of total costs) and workers (70% of total costs). The study highlights the difficulties and constraints of controlling advanced stages of invasions.
Trial of herbicide control methods for sisal Agave sisalana in the arid island environment of Aldabra Atoll, Seychelles
van Dinther M., Bunbury N. & Kaiser-Bunbury C.N. (2015), 12, 14-18
Sisal Agave sisalana is an invasive alien plant species of concern at the UNESCO World Heritage Site of Aldabra Atoll in the Seychelles. Physical control efforts since the 1970s to remove sisal from Aldabra have only been partially successful because the roots cannot be completely removed, resulting in continuous control efforts. We conducted a seven month herbicide trial, using different herbicide concentrations with two application methods, to determine the most effective and feasible control method for sisal. We also checked effects on surrounding native plants. The highest treatment mortality was from 50% herbicide concentration applied directly to the cut growth tip, which resulted in 80% sisal mortality after four months. Fewer treated plants died at lower herbicide concentrations and more small plants died than large plants. No sisal plant died that was foliar sprayed, only cut, or in the control group. There were no visible negative effects of any treatment on the surrounding native flora. The results indicate that chemical control of sisal is effective at high herbicide concentration applied directly to the cut growth tip. A full-scale eradication of sisal from Aldabra has been started based on the trial results.
Bracken Pteridium aquilinum control on small conservation sites, Miserden, UK
Grange I. (2013), 10, 16-19
The objective of this work was to test the effectiveness of reducing bracken density by cutting once or twice a year, or by hand-pulling, compared with a control. The experimental site had already been managed by annually cutting bracken for about 10 years. One year after the management treatments were applied to the plots, both the cut treatments had significantly shorter fronds than the control, but no difference was seen with the pulling treatment. Frond densities and frond coverage were not significantly different from the control, with each showing high variability between plots.
Estimating the minimum salinity level for the control of New Zealand Pygmyweed Crassula helmsii in brackish water habitats
Dean C., Day J., Gozlan R.E., Green I., Yates B. & Diaz A. (2013), 10, 89-92
Crassula helmsii is a semi-aquatic, invasive macrophyte, which has become abundant in wetland habitats across Europe. This species is of conservation concern because heavy invasions form dense carpets within which few other plants species occur. C. helmsii is known to be killed by inundation with seawater, but published information on its response to inundation by less saline water is limited. Growth trials were conducted to investigate the levels of salinity required to kill this species. We found a linear negative relationship between growth rate and salinity across the range from 2 – 8 ppt, but that 8 ppt was required to kill C. helmsii. These findings suggest that C. helmsii growth could be controlled by inundation with saline water of 8 ppt. This may present a method for reducing the negative effects of salt water on co-occurring species, and thus the next stage will be to determine the efficacy of this method in field trials.
Eradication of New Zealand flax Phormium tenax on Inaccessible and Nightingale Islands, Tristan da Cunha
Ryan P.G., Glass P.G., Glass T., Barendse J. & Cuthbert R.J. (2012), 9, 58-62
New Zealand flax Phormium tenax was introduced to Tristan da Cunha, an island in the central South Atlantic Ocean, in the 1800s. During the following century it was transferred to two other islands in the Tristan archipelago: Inaccessible and Nightingale Islands. Although not an aggressive invader, flax spread on both islands threatening their status as among the least disturbed temperate islands remaining in the Southern Ocean. In 2004 an eradication programme was initiated on both islands to clear flax using a combination of uprooting, cutting, crushing and spraying with herbicide. Despite some regrowth, follow-up operations greatly reduced the number of flax plants. Established plants are now confined to about 300 m of cliffs at the Waterfall on Inaccessible Island where clearing is hampered by the steep terrain. Further follow-up management is planned until the plant is eradicated from both islands.
Control of giant reed Arundo donax on Vila Franca do Campo Islet, Azores, Portugal
Silva C.M.N., Silva L., Oliveira N., Geraldes P. & Hervías S. (2011), 8, 93-99
The non-native, invasive giant reed Arundo donax covers an estimated 30% of Vila Franca do Campo Islet (Azores). It blocks the entrance of Cory's shearwater Calonetris diomedea borealis nest burrows and out-competes threatened Azorean endemic flora. Three A. donax control methods were tested in 90, 1m2 plots, and cost-effectiveness of each determined using a Simple Additive Weighting Model. The most effective control method was cutting and removal of reed stems followed by two glyphosate-based foliar herbicide applications (one in May and another in late October i.e. corresponding to before and after the Cory's shearwater breeding cycle). After one year, 92% of giant reed was eradicated at an estimated cost of €8,000 per hectare.
Strategies to eradicate the invasive plant procumbent pearlwort Sagina procumbens on Gough Island, Tristan da Cunha
Visser P., Louw H. & Cuthbert R.J. (2010), 7, 116-122
In 1998, procumbent pearlwort Sagina procumbens a non-native and invasive plant was discovered on Gough Island (Tristan da Cunha). Efforts to eradicate this species have been underway since 2000. To date it has been restricted to a small (400 m length; approximately 1.2-1.6 ha area) but complex stretch of coastal cliffs. Measures of seed density, based on germination trials of soil samples collected from Sagina infested areas, indicate that 'standard eradication' methods (digging up individual plants, heat-treating soil and spot-treatment with herbicides) in place over the last 10 years have resulted in a three orders of magnitude reduction in the seed load. However, around 200 seedlings per m² continue to be recorded due to germination from seeds within the soil. In 2008-09 we investigated the effectiveness of three methods designed to eradicate Sagina on Gough: 'standard eradication' based on methods used in previous years (n = 5 plots); monthly 'herbicide treatment' across the whole plot (n = 4 plots); and 'soil stripping' where all plants and soil was removed down to bedrock (n = 2 plots). Sagina plants remained present within the standard eradication plots, with an average of 64 ± 79 (range 6 - 200) plants recorded per plot cleared in 8-months of monitoring. No Sagina plants were found in herbicide treated plots, although this method is unlikely to tackle the problem of dormant seeds remaining within the soil. Soil stripping was effective at removing the seed bank and only five and 33 plants were found over the 8-months monitoring period. We recommend that a combination of monthly herbicide spraying across the whole infested area (to prevent plants maturing and setting seed) and a programme of soil stripping (working from the outer edge of the plants range) to remove the seed bank, be utilised in order to provide a potential method to eradicate Sagi from Gough.
Large-scale eradication of New Zealand pygmy weed Crassula helmsii from grazing marsh by inundation with seawater, Old Hall Marshes RSPB reserve, Essex, England
Charlton P.E., Gurney M. & Lyons G. (2010), 7, 130-133
The invasive New Zealand pygmyweed Crassula helmsii was eradicated from approximately 120 ha of coastal grazing marsh at a site in southeast England by shallow flooding of the area with sea water for 12 months. This method of eradication can only be used where saline water can be held on a site (with due regard for potential impacts on non-target species). We have not come across an example of successful C. helmsii eradication on this scale by using other methods.
Evaluation of a large-scale invasive plant species herbicide control program in the Berkshire Taconic Plateau, Massachusetts, USA
McAlpine L. & Porder S. (2009), 6, 117-123
In the late 1990s, The Nature Conservancy (TNC) documented a rise in five invasive plant species, barberry Berberis thunbergii, bittersweet Celastrus orbiculatus, garlic mustard Alliaria petiolata, buckthorn Frangula alnus, and honeysuckle Lonicera morrowii on the periphery of the relatively intact and uninvaded 14,600 ha Berkshire Taconic Plateau in Massachusetts (USA). The Plateau comprises an ecologically significant block of forest. In response, TNC began a large-scale herbicide-based control program on approximately 3,600 ha of land with the goal of reducing invasive cover to less than 10%. Our objective was to evaluate the efficacy of this effort, but this was hampered by a dearth of untreated control sites and pretreatment data on invasive species cover. Four sites (three treated, one untreated) on the plateau periphery similar in understory vegetation, overstory cover, slope, and proximity to a hiking trail were surveyed and compared. Across each site, native and invasive plant percent cover within 44, 1m² plots was measured, and native and invasive presence absence recorded on an additional 2,000m² area. All five target invasives were present at all four sites 5-years post-treatment. In two of the treated sites, invasive percent cover significantly exceeded the 10% goal, largely due to the abundance of garlic mustard. Without garlic mustard, all the sites (including the untreated one) had < 10% invasive cover. Surprisingly, the high level of invasive cover did not have a significant negative impact on native cover (native species richness was not quantified), although a hypothesized negative relationship was invoked as justification for the herbicide treatment.
Given the difficulty in finding comparable treated and untreated sites after herbicide application, we suggest 1) that quantitative data on invasive abundance be gathered prior to a control program and 2) that treated and untreated plots be allocated to monitor outcomes. Without this, determination of effectiveness is difficult and likely to be inconclusive.
Effects of grey willow Salix cinerea removal on the floristic diversity of a wet dune-slack at Cabin Hill National Nature Reserve on the Sefton Coast, Merseyside, England
Smith P.H. & Kimpton A. (2008), 5, 6-11
Cutting, removal and herbicide stump-treatment of dense grey willow Salix cinerea scrub from a 1 ha wet dune-slack was undertaken in a northwest England National Nature Reserve. This resulted, over the next two years, in colonisation by 139 vascular plant taxa. Of these, 11 are nationally or regionally notable, with 28 being new reserve records. The high proportion of ruderal plants in the first year was largely replaced by dune species in the second season after scrub removal.
Effectiveness of chemical and mechanical bracken Pteridium aquilinum control treatments in northern coastal heathlands on the island of Lygra, Hordaland, Norway
Måren I.E., Vandvik V. & Ekelund K. (2008), 5, 12-17
In a 7-year field experiment undertaken in western Norway, the efficiency of four bracken control measures on a heathland was investigated: application of two herbicides i) AsuloxÂ®- and ii) GratilÂ®-with follow-up annual cutting; iii) annual cutting; and iv) biannual cutting. Assessments were also made as to what extent the characteristic species composition and vegetation structure of heathlands were restored, and effects of the herbicides on non-target plant species commonly found on heaths. Fastest reduction in bracken cover resulted from herbicide application, but cutting proved equally efficient in the longer term; Asulox and biannual cutting both reduced bracken cover from over 70% to below 10% in 2 years, while annual cutting achieved this in 5 years. Gratil failed to have long-term effects. Species composition progressed towards a desirable heathland vegetation community, but successional trajectories differed, and Asulox had minor unintended effects on a number of heathland plants, including heather Calluna vulgaris, several grasses, herbs and mosses. These effects could not be predicted by functional group or other simple species characteristics. However, any short-term detrimental effects of Asulox application were considered to be outweighed by the beneficial longer term effects of reduced bracken cover, which allowed re-establishment of the heathland flora.
Successful transport and quarantine of materials using sealable plastic barrels, Round Island, Mauritius
Tatayah R.V.V., Birch D., Haverson P. & Zuel N. (2007), 4, 13-15
A practical, cost-effective method of packing securely items destined for Round Island was required. Since 2001, re-sealable plastic barrels have been used for the transport of almost all materials onto the island. No unwanted 'stowaway' species have since been recorded when using this method of packing. The barrels are very versatile and are increasingly used in the transport of materials to other Mauritian offshore islets.
Controlling invasive willow Salix spp. on wet grassland by grazing with Hebridean sheep, Kingfishers Bridge, Cambridgeshire, England
Gulickx M.M.C., Beecroft R.C. & Green A.C. (2007), 4, 33-34
On recently created wet grassland at a site in eastern England, willow Salix spp. was invading. It was cut then 30 adult female Hebridean sheep and a Texel ram were introduced to control any regrowth. The sheep have kept the site clear of both newly sprouting willow shoots and willow seedlings.
Removal of invasive floating pennywort Hydrocotyle ranunculoides from Gillingham Marshes, Suffolk, England
Kelly A. (2006), 3, 52-53
Non-native floating pennywort Hydrocotyle ranunculoides had colonised and grown to dominate parts of Gillingham Marshes, eastern England, where it was outcompeting native plants. Removal was undertaken using a mechanical digger and by monthly picking by hand. This greatly reduced its cover but did not completely eradicate it. The native aquatic vegetation is re-establishing.
Controlling New Zealand pygmyweed Crassula helmsii using hot foam, herbicide and by burying at Old Moor RSPB Reserve, South Yorkshire, England
Bridge T. (2005), 2, 33-34
Three methods of New Zealand pygmyweed Crassula helmsii control were undertaken: using 'Waipuna' hot foam, spraying with Glyphos bioactive, and by smothering and burying. Spraying with either 'Waipuna' or Glyphos killed 50% of the vegetation and stopped Crassula from spreading, but did not eradicate the weed. Smothering and burying killed all plants (100% mortality), but proved very labour intensive and causes much disturbance.
Killing sweet chestnut Castanea sativa coppice stools by cutting and herbicide treatment, Blean Woods RSPB Reserve, Kent, England
Walter M. (2005), 2, 35-36
Sweet chestnut Castanea sativa coppice was controlled by five different methods: repeated cutting,amcide poured into drilled holes, herbicide painting of stumps, weed-wiping of first year growth, and knapsack spraying of regrowth. The most effective and efficient method was to cut the coppice stools and subsequently knapsack spray the first year regrowth with herbicide.
Rhododendron Rhododendron ponticum control by mulching, cutting and herbicide application at Blean Woods RSPB Reserve, Kent, England
Walter M. (2005), 2, 39-40
Measures were undertaken to attempt to eradicate invasive rhododendron Rhododendron ponticum. Mechanical removal is quick, but expensive (£1,000/day) and has a high potential for damaging the soil and coppice stools. Manual removal is labour intensive (120 man-days/4 ha), but was less damaging and could be applied in areas in which machinery could not be used. Weed-wiping regrowth was slower but more effective (70% kill rate) than spraying (40-50% kill rate).
Controlling New Zealand pygmyweed Crassula helmsii in field ditches and a gravel pit by herbicide spraying at Dungeness RSPB Reserve, Kent, England
Gomes B. (2005), 2, 62-62
A programme was introduced to eradicate invasive New Zealand pygmyweed Crassula helmsii by Reglone herbicide treatment. In response, 70% of pygmyweed was killed. Follow up spraying of regrowth was partially successful but some re-growth is noticed annually.
Control of New Zealand pygmyweed Crassula helmsii by covering with black polythene at The Lodge RSPB Reserve, Bedfordshire, England
Wilton-Jones G. (2005), 2, 63-63
At The Lodge RSPB Reserve, an attempt was made to eradicate invasive New Zealand pygmyweed Crassula helmsii that had colonised a pond by covering with black polythene. Pygmyweed was completely eradicated but re-colonised from plants in marginal vegetation in areas not covered with polythene.
Spray treatment of bracken Pteridium aquilinum using Asulox herbicide at Blackhill, Dorset, England
Liley D. (2005), 2, 103-104
An area of silver birch Betula pendula (40% cover) was cleared during the winter of 1995-1996. Two summers later, the cleared area and an adjacent area of open heath were sprayed with Asulox herbicide to control invasive bracken Pteridium aquilinum growth. Seven years after the last spray treatment, bracken was dominant throughout the area (median cover in sample plots 80%; cover estimate range 40%-90%). Whilst achieving short-term success, longer term evidence therefore suggests that bracken management needs to be ongoing at this site.
Mechanical clearance of maritime pine Pinus pinaster using a shear-head timber processor at Barnsfield, Dorset, England
Liley D. (2005), 2, 105-106
At a site in southern England in September 2004, about 4 ha of mature, dense, non-native, maritime pine Pinus pinaster was cleared using a shear-head timber processor. One year later in August 2005, the cleared area was predominantly covered in purple moor-grass Molinia caerulea (approx. 80% cover). The remaining 20% was either bare ground (approx. 15%) or mature heather Calluna vulgaris and gorse Ulex plants (less than 5% cover) present prior to clearance, but no heather seedlings were found. There was no evidence of any pine regeneration.
Mechanical clearance of Scots pine Pinus sylvestris using a shear-head processor at Barnsfield, Dorset, England
Liley D. (2005), 2, 107-108
In August 2004, an area of just over 1 ha of dense, mature Scots pine Pinus sylvestris was cleared using a shear-head timber processor. Prior to the clearance, the area supported little heathland vegetation and was predominantly bare ground with some bracken Pteridium aquilinum underneath the dense pine canopy. One year after the clearance, heather Calluna vulgaris seedlings had become established. Evidence suggests that control of bracken and tree seedlings may be required as part of long-term management in order to restore and maintain an open heath.
Mechanical clearance of Scots pine Pinus sylvestris and rhododendron Rhododendron ponticum from lowland heathland at Hurn, Dorset, England
Liley D. (2005), 2, 109-110
Approximately 0.5 ha of dense, mature Scots pine Pinus sylvestris and rhododendron Rhododendron ponticum was cleared using a shear-head timber processor. Prior to clearance the area under the canopy supported little heathland vegetation. One year later, heather Calluna vulgaris seedlings had become established; other heathland vegetation included purple moor grass Molinia caerulea and cross-leaved heath Erica tetralix. There was also evidence of vigorous rhododendron regrowth from the cut stumps.
Comparison of two chemicals used to control Rhododendron ponticum at Blackhill, Dorset, England
Liley D. (2005), 2, 129-129
Two different herbicides were used to treat young Rhododendron ponticum plants on an area of heathland in June. Three months later, of 157 plants sprayed with Glyphagen (Roundup), all but 11 had died (93% kill rate), while of 161 plants sprayed with Garlon with additions of Mixture B (a wetting agent), all but five had died (97% kill rate).
Chemical control of birch Betula regrowth on heathland at West Moors, Dorset, England
Liley D. (2005), 2, 130-130
During the winter of 2000-2001, approximately 2.4 ha of dense (75-100% tree cover) and 0.6 ha of medium (25-50% tree cover) birch Betula was cut and removed. In August 2002, the cleared birch had regenerated resulting in a dense stand of 2 m high birch. The regrowth was sprayed with Timbrel using knapsack sprayers. The regrowth kill rate of sprayed areas was 100%; no regrowth was subsequently recorded.