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Home , Canopy (grape), Xylella fastidiosa

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Forest Research scientists Ana Perez-Sierra and Joan Webber, impacts range from wilting, growth stunting and scorch, to dieback and with Animal and Plant Health Agency inspectors Edward the death of entire plants. In trees for Birchall and Lucy Carson-Taylor, provide an update on this example, the disease starts with withering 9emerging risk to plants and trees across . and desiccation of the terminal , but as the damage expands through the , trees collapse and die. Typically on trees such as , elm What is Xylella? 2 Where has the disease plane, (Acer spp.) and , 1 come from? visible symptoms caused by Xylella Xylella, or more properly Xylella fastidiosa, Before the findings in Europe,Xylella fastidiosa ssp. multiplex are mainly leaf is a disease causing bacterium that can was encountered mainly in the Americas. scorch so in the USA the disease is known infect many woody plants including Subspecies fastidiosa is found in Central as bacterial leaf scorch or BLS. Some broadleaved trees. There are at least four America, and , effects, however, can be more severe accepted subspecies of Xylella which where it affects , grapevines and and include twig and branch dieback or attack various plant types inciting different and almond plants. Subspecies growth stunting of the entire tree. The types of symptoms. They are - multiplex has mainly been found in the characteristic leaf symptoms which are • Xylella fastidiosa ssp. fastidiosa USA and probably has the widest host most visible in later summer include • Xylella fastidiosa ssp. pauca range which includes trees such as oak, browning at the leaf margins (not along • Xylella fastidiosa ssp. multiplex elm and plane. Multiplex is considered to the main veins), often with a yellow edge • Xylella fastidiosa ssp. sandyi pose the greatest risk to trees in the UK. to the browned areas. However, other Until recently, Xylella was only known disorders can cause similar symptoms (see from the Americas and Taiwan, but it first What does Xylella do to Disorders box). became notorious in Europe following 3 infected plants? reports of the rapid decline and death of The bacterium invades the 4 How does Xylella ancient olive trees in the region transporting vessels in plants, spread? of southern in 2013. X fastidiosa was blocking water movement and causing In the natural environment Xylella is confirmed as the cause and the subspecies symptoms that initially resemble water exclusively transmitted by insects such as identified asX fastidiosa ssp. pauca. Now stress. Depending on the susceptibility of and froghoppers which feed around a million trees in southern Apulia affected plants and the Xylella subspecies, on xylem fluid. There are various insect are affected by the disease, referred to as Olive Quick Decline Syndrome (OQDS). Subsequently other Xylella outbreaks in Europe have been found in France, Spain and (see Timeline) with a wide range of plant species affected. In addition to X fastidiosa ssp. pauca causing OQDS in Italy, subspecies fastidiosa and multiplex have also been found in other European countries. To control this bacterial pathogen which is now treated as a quarantine pest, stringent measures are in place. All EU Member States are required to eradicate any outbreaks, or if that is impossible, to prevent further spread. Figure 1 Olive quick decline syndrome (left) Early Xylella fastidiosa symptoms (branch wilting) on an olive tree in September 2014; (right) symptom development on the same tree by May 2016. (Courtesy of Donato Boscia from CNR-IPSP, Italy)

Xylella timeline 2013 2015 2016 (July) 2016 (October) 2017 (August) 2017 (June) X fastidiosa X fastidiosa ssp. X fastidiosa Infected almond Grapevines were X fastidiosa ssp. The most recent ssp. pauca multiplex identified ssp. fastidiosa trees were found also found to multiplex was figures from first confirmed affecting several confirmed in a on Mallorca and be affected on found on the Europe suggest in causing plant species German glasshouse then other affected Mallorca. The Spanish mainland around 150 shrub devastation to in France and on an oleander hosts on and Balearics now have (south of Valencia) and tree species olive plantations in . plant and then Menorca. many outbreaks on dulcis have been infected. . on , involving three (almond). Erysimum and subspecies of X Streptocarpus. fastidiosa.

42 FORESTRY & TIMBER NEWS • December 2017 CONFOR.ORG.UK species in Britain that could become Figure 2 Xylella bacterial leaf scorch symptoms on tree foliage (left) American sycamore vectors if Xylella was introduced, including ( occidentalis); (centre) English oak (Quercus robur); (right) elm. (Courtesy of the common froghopper (meadow Theodore D. Leininger, USDA Forest Service, Bugwood.org, John Hartman, University of spittlebug). Although these insects Kentucky, Bugwood.org and Sandra Jensen, Cornell University, Bugwood)org) generally only fly short distances they can be moved much further by the wind. As they feed, they pick up the bacterium from Disorders with similar symtoms infected plants and pass it onto healthy plants. Movement in trade of infected Several disorders produce symptoms similar to those caused by Xylella fastidiosa. plants also aids disease spread. • Horse chestnut trees commonly suffer from a fungal disease which causes a brown leaf blotch with a yellow halo. The horse chestnut leaf miner also damages foliage but 5 How likely is it that Xylella might causes an inter-veinal browning of rather than marginal browning. establish? • Elms suffer from Dutch elm disease which also causes wilting and browning of foliage. Xylella has not yet been found in the UK, • Plane trees suffer from a fungus called anthracnose which causes twig death and leaf but if it arrives at least one subspecies is blight. can also cause yellowing and distortion of young plane leaves. likely to be able to survive and establish • Drought stress can cause cupping and browning at the leaf margins. most probably in the warmer parts of the UK, especially in regions with minimal episodes. Xylella fastidiosa ssp. multiplex 7 What happens if Xylella is 8 Good practice to combat which infects various forest tree genera found in UK? Xylella is active in temperate regions of North An outbreak in the UK could lead to • If importing plants, ensure that plant America. destruction of host plants within 100 m passports arriving with host plants are and a 5 km movement ban for ‘specified’ correct and keep the passports to aid 6 What are we doing plants for five years. Any findings will dealt trace back if necessary. to prepare? with to reflect risk and evidence of spread. • Source from known suppliers or The Forestry Commission undertakes Where Xylella is found on a plant and visit suppliers to view their procedures, targeted annual surveys of susceptible the disease has spread or there is risk biosecurity arrangements and the plants tree species as part of the surveillance that spread has occurred, then a 5 km they grow. See web resources. activities against X fastidiosa. The Animal demarcated area is required - the size and • Ensure imported plants originate from and Plant Health Agency (APHA) also how long it remains in place will depend and are sourced from disease free areas. conducts official surveys forX fastidiosa on a risk assessment. For regularly updated details on affected >> and works with businesses which import If infected plants are recently arrived susceptible plant species. Landscapers, but vectors carrying Xylella are not designers, retailers and anyone directly found, then a demarcated area is not importing plants are now subject to the needed. Plant Health Services will require same stringent requirements as growers destruction of the infected plants and any and suppliers. Prior to the movement of nearby potential hosts will probably have all potential Xylella ‘host plants’ across to be destroyed as well. the EU they must have been officially For isolated outbreaks resulting from inspected and be accompanied by a plant introductions of infected plants where passport to show they have been sourced there is robust evidence that spread has from disease free areas/sites. High risk not occurred and other actions are taken, hosts such as , Lavandula dentata, the buffer zone width may be reduced oleander, Olea europaea, Polygala to 1 km and restrictions revoked after a myrtifolia and Prunus dulcis have extra minimum of 12 months. requirements. Figure 3 Laboratory processing of tree foliage samples at Forest Research for the detection of Xylella fastidiosa (Forestry Commission).

CONFOR.ORG.UK FORESTRY & TIMBER NEWS • December 2017 43 PLANT HEALTH VIEW FROM THE EMERALD ISLE SÉAN LENIHAN

>> areas, known plant hosts and legislation, Ash dieback update Knowledge Transfer to the processing and see web resources. Since it was first discovered in County sale of first thinnings and firewood. There • Isolate or quarantine new plant batches Leitrim in October 2012, Ash dieback has are 2,000 owners now officially registered and monitor them during the growing been confirmed in 384 forest plantations, with Producer Groups which represents season for any symptoms – whilst not and is now present in every county in the about 20% of all private forest owners. a legal requirement it is good practice Republic. These were the official figures at Some of the groups have employed for- to place ‘imported’ hosts of Xylella in a 31/7/2017 but there has been many reports esters to advise owners on planting, man- quarantine area – ideally some distance from forestry consultants of new outbreaks agement etc. which has been a cause of away from other host plants and under in August, September and October. concern for some forestry consultants and physical protection if possible. If an In response to the dramatic rate of in- companies due to the fact that the groups outbreak is confirmed all ‘host’ material crease in incidents of the disease, the For- have received state funding from the Rural within 100m will be destroyed. est Service introduced a more pragmatic Development Programme and some are • For contractors/designers, ensure that policy for the removal and treatment of the now effectively in competition with private plants are ordered early and monitor infected ash crops this year. sector businesses. for disease in a low risk area before final The previous one-size-fits-all which One of the first groups to get estab- planting. stipulated 100% clearance and disposal of lished was the Donegal Woodland Owners • Label and keep records of all received all material by burying in pits or trenches Co-Op which markets itself as a wood sup- batches of plants including where they (unless it was fit for firewood) has been ply co-operative actively involved in thin- came from and when. Also maintain modified by the introduction of a three cat- ning and sales of firewood, and which has records of pesticide treatments. egory classification system with associated being pro-active in promoting the use of • Destroy old or unusable plants. requirements: woodfuel in Donegal. Another progressive • Comply with the UK national • Class 1: <7m top height group is the Irish Wood Producers which requirements to notify the UK Plant Health Remove all ash trees has 650 members based in Wexford, Kilk- Service about certain species of plants • Class 2 > 7m < 15m top height or 18cm enny and Laois. under the ‘EU Plant and Tree notification DBH or 25 years old scheme’. Remove infected individual trees Afforestation outturn 2017 • Class 3 >15m top height or 18cm DBH or There is a real probability that the af- 25 years old forestation target of 7000ha will not be If you suspect a plant is Consultant produces Management Plan achieved in 2017 unless there is an unprec- 9 affected by X fastidiosa for owner which may or may not include edented level of planting in the final two Suspected X fastidiosa outbreaks must partial removal. months of the year. To date approximately be reported to the relevant Plant Health The requirement to bury all infected ma- 4250ha have been planted and realistical- Service authority: terial is now optional with onsite windrow- ly a final outturn of 5500ha would be an • For Forestry Commission use the Tree ing now permitted. excellent achievement at this stage. Many Alert form: http://www.forestry.gov. Site clearance grants of E1500/ha are reasons have been put forward for the uk/treealert available for Classes 1 and 2, with a replant- drop in in planting levels, from high pric- • For England and Wales, contact your ing grant of E3300/ha for a conifer replace- es for land leasing, expansion in the dairy APHA Plant Health and Inspector ment crop, and E5000/ha for a broadleaf sector post-quota removal, sterilisation or the PHSI Headquarters, Sand Hutton, species. In addition the existing Broadleaf of large area for environmental reasons York. Tel: 01904 405138 or email: Thinning Grant of E750/ha can be availed where no planting is permitted, higher lev- [email protected] of by owners in Class 2 and 3 where the els of bureaucracy with the Forest Service, • For Scotland, contact the Scottish partial felling of infected trees is planned. and the new requirement to erect site no- Government’s Horticulture and With an estimated 20,000ha of ash tices on the land where a licence to plant Marketing Unit by email: planted in the Republic between 1994 and is being sought, and the new mechanism [email protected] 2011 growers and foresters will be dealing which allows objections from the public • For Northern Ireland, contact the with the consequences of Ash Dieback for to the issuing of planting licences. Even DAERA Plant Health Inspection many years to come. though the new afforestation licence re- Branch: Tel: 0300 200 7847 email: quirements were only introduced in June [email protected] Forestry producer/owner groups 2017, there has been 15-20 objections to It is a major indication of how the private the issuing of new licences by members of forest industry in Ireland is maturing, and the public which does not augur well for now entering a new phase, that Forestry the future. producer/owner groups which commenced in the mid-noughties have become firmly Timber Prices established. This development can rightly Timber prices have remained steady FTN WEB RESOURCES be regarded as a landmark one for the pri- throughout 2017 with roadside prices cur- Find links for: vate forest industry in Ireland. rently averaging: E Guidance on high risk hosts The Forestry Division of TEAGASC the • Commercial sawlog: 72 E Information on affected areas, state agency with responsibility for Agri- • Pallet: €46 E hosts and legislation cultural R&D in Ireland were instrumental in • Pulp: 27 Additional information on UK starting and organising the various groups Demand is strong for all grades although Plant health nationwide, and there are now 20 plus pallet roadside prices have softened a lit- www.confor.org.uk groups covering the entire country with tle from since the first quarter of 2017. varying degrees of involvement from basic www.kestrelforestry.ie

CONFOR.ORG.UK FORESTRY & TIMBER NEWS • December 2017 45