Future Forest Health Early detection and mitigation of invasive pests

NordGen Forest Workshop 2019

Hótel Örk, Hveragerði, 16 September 2019

Workshop Abstracts

Invasive pests and diseases on in the Nordic countries: Iceland Brynja Hrafnkelsdóttir1*, Guðmundur Halldórsson2 1Icelandic Forest Research Mógilsá, 162 Reykjavík; 2Soil Conservation Service of Iceland, Gunnarsholt, 851 Hella *[email protected]

Workshop Abstract Downy birch ( Ehrh.) is and may contribute to tree death (Hall- the only native forest forming tree spe- dórsson et al, 2013). The following spe- cies in Iceland (Aradóttir & Eysteinsson, cies can, therefore, be ranked as inva- 2005). Its present distribution is 1.5% of sive: the land area, but is estimated to have been around 25% at the time of settle- ment. Downy birch is an important tree • Birch-aspen leafroller Epinotia so- in Icelandic ecosystems and forestry landriana was first introduced to and presently there are ambitious plans Iceland in 1907, but is now found to increase its distribution. in lowlands all over Iceland. In Iceland the larvae feeds primar- Outbreaks of native on birch, ily on downy birch, although it causing tree death, are well known can be found on other as from old annals and reports. These out- well. It has caused total defolia- breaks were most likely caused by the tion of large areas of birch larvae of notana and Rheumap- woodland and contributed to tera hastate. Local outbreaks in south- significant tree death (Hallgríms- east Iceland are known to have been son et al, 2006). caused by Erannis defoliaria, which is only found in this area. • Winter bru- mata was first introduced in 1928 Downy birch is host to two tree dis- and feeds on various trees and eases, birch rust Melampsoridium betu- shrubs and can cause serious de- linum and witch's broom Taphrina bet- foliation (Ottósson, 1982). It is ulina and 31 herbivore spe- mainly confined to urban areas, cies. Both diseases are native but about except in southern Iceland one third of the pests species (10) where it can also be found in on birch were introduced after 1900, birch woodlands (Hallgrímsson and are therefore listed as non-native. et al, 2006). The effect of those herbivores on birch can be very variable. Some have caused • Heringocrania unimaculella is a total defoliation of large areas of wood- small leafmining moth that land which has sometimes leads to tree feeds only on birch and was first death on significant areas (Halldorsson recorded in Iceland in 2005. It et al, 2013). Other only inflict minor has since introduction been damage but may reduce growth and spreading and has caused defo- can possibly increase plants susceptibil- liation of downy birch in South, ity to other stresses. Four, out of the ten Southwest and North Iceland. non-native pest species that feed on • Scolioneura betuleti is a leafmin- birch in Iceland, cause serious damage ing sawfly that was first

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recorded in Iceland in 2016 and Tipula paludosa was introduced in feeds on some birch and alder 2001 and has been confined to South species. Since then it has its dis- and Southwest Iceland. The larvae feed tribution has been expanding on the roots of many plants and can fast and it has been causing se- cause local damage. The sixth species, vere damage, especially in the the meadow spittlebug Philaenus spu- SW part of Iceland. marius, was introduced in 1983. It feeds on leaves of many plant species and is The six other non-native insect species not considered to cause any significant which can be found feeding on birch damage. are all polyphagous, except the bronze alder moth Argyresthia goedartella, In Iceland it has previously been shown which was first recorded in Iceland in that recent increase in introduction of 2012 and feeds on the catkins of alder insect pest species on trees as well as and birch. It is not considered to cause changes in outbreak patterns of various any damage. Three weevil species: Oti- species are linked to increased mean orhyncus singularis, Barypeithes pellu- annual temperatures (Halldórsson et al, cidus and Otiorhyncus ovaturovatus 2013). Therefore, it is likely that we will were introduced in 1968, 1980 and 1987, see more serious insect outbreaks on respectively. The larvae feed on roots birch in the near future, both from the and the beetles on bark and leaves. All invasive pest species listed above and are limited to urban areas and cause lit- new pest and diseases that have not tle or no damage. The European crane been introduced yet.

References: Aradottir, AL, & Eysteinsson, Th (2005). Restoration of birch woodlands in Iceland. Restoration of boreal and temperate forests. CRC Press, Boca Raton, 195-209. Halldórsson, Gudmundur, Sigurdsson, Bjarni D, Hrafnkelsdottir, Brynja, Oddsdóttir, Edda, Eg- gertsson, Ólafur, & Ólafsson, Erling (2013). New arthropod herbivores on trees and shrubs in Iceland and changes in pest dynamics: A review. Icelandic Agricultural Sciences (26), 69-84. Hallgrímsson, Helgi, Halldórsson, Guðmundur, Kjartansson, Bjarki Þ, & Heiðarsson, Lárus (2006). Birkidauðinn á Austurlandi 2005 [The birch death in East Iceland in 2005]. Ársrit Skógræktarfélags Íslands 2006 (2), 44-53. [In Icelandic]. Ottósson, Jón Gunnar (1982). Skordýrin og birkið [The insects and the birch]. Ársrit Skógræktarfélags Íslands 1982, 3-19. [In Icelandic].

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Threats posed to natural forests by international movement of pests and diseases Professor Hugh Evans Fellow of Forest Research, Alice Holt Lodge, Farnham, Surrey, GU10 4LH, UK [email protected]

Workshop abstract Trees are subject to a wide range of As an island, the United Kingdom has a biotic and abiotic factors that can result relatively impoverished fauna in damage and death if the balance of compared with continental Europe so factors is altered to favour pest that both the indigenous and invasive organisms, including both insects and components of its fauna are smaller pathogens. In a natural, co-evolved sy- than its near neighbours. However, the stem, there is generally a series of long history of trading globally and the opportunities and constraints affecting near proximity of the European land- an organism that tends to maintain it at mass means that there is an increasing endemic levels. Disruption of this list of new pest associations in the UK. endemic status can arise for many This will be described in more detail in reasons, acting either individually or, the presentation, but some notable more usually, in concert. Examples of examples serve to illustrate the issue of disruptors include: opportunity for new pests to arrive or native insects to become pests when • Invasion of an area by an exotic presented with exotic host tree species. species • Planting of exotic host tree Defoliators species used by both invasive Most of the issues from defoliators and native species have been caused by sawflies • Loss of natural enemy impacts (Hymenoptera) and that normally constrain popu- () with the majority of lation growth incursions being linked to importation • Stochastic events such as storms, of live plants for planting, a very high- droughts, fires, etc. that reduce risk pathway. Notable recent incursions the natural defences of trees have been gypsy moth, Lymantria dispar making them more vulnerable and oak processionary moth, Thaumet- to attack opoea processionea in the south of Eng- • Climate change that can impact land, and tree lappet moth, both the fauna associated with pini, in Scotland. In all trees and the trees themselves. cases initial populations were small Invasions of organisms that have and management efforts were focused become pests have been noted on containment but not eradication. A increasingly in the literature variant on the theme of exotic (Brockerhoff & Liebhold 2017) and the associations applies to the major out- trend appears to be continuing despite breaks and tree mortality caused to international phytosanitary rules to lodgepole pine (Pinus contorta) minimise the risks of pest movements plantations in Scotland caused by the between countries and ecosystems. native pine beauty moth, Panolis flammea. This moth remains at

5 endemic levels on its native Scots pine planipennis) is native to Asia but has () host but exploited the established in North America with widespread planting of lodgepole pine devastating consequences for both leading to extensive tree mortality. native and planted ash trees across the continent. It is easily carried on ash Bark and wood-boring beetles wood and wood products and has now Other notable examples of alien been found on the western borders of invasive pests are bark beetles in the and into . This poses a family Curculionidae: Scolytinae. Foll- significant further threat to ash trees owing the establishment of Ips across Europe to add to the extensive sexdentatus in the early part of the 20th mortality caused by the fungus century, there have been incursions of Hymenoscyphus fraxineus. As evidenced Ips cembrae in the 1950s and at the end by the experiences in North America, of 2018, Ips typographus. The latter, in there is a high risk of a lag period of particular, has been intercepted many years between initial invasion frequently during inspections of and eventual detection of infestations imported wood and also in pheromone (Herms & McCullough 2014) and this traps at the ports, but was only found requires development of optimal sur- breeding at a single woodland in Kent veillance to determine where to place in November 2018. Other dangerous scarce survey resources. The closely pests have also been found in Kent in related bronze birch borer (BBB – Agrilus recent years, including Asian longhorn axius) which is native to North America beetle, Anoplophora glabripennis in and regarded as a minor pest of 2012 which has now been declared weakened trees there, poses a much eradicated after an intensive survey bigger threat to European birch forests. and felling campaign. More recently, Although relatively little detailed study the oriental chestnut gall wasp, has been carried out on its biology and Dryocosmus kuriphilus has been found pest status, recent observations of in Kent and is spreading slowly to other rapid tree mortality on exotic plantings areas in the south of England. The close of in the USA, indicates proximity to the main channel ports that if it did establish in Europe the and the warmer climate in that area are impact would be significant. Pathways among the potential factors making for this pest would include any birch the south east of England prone to new wood products, firewood and, alien invasive species. potentially, plants for planting. These, and many other insects and Whilst the list of invasive pests pathogens, illustrate that pathways for continues to increase, it is important to international movement of pests and assess measures not only to attempt to their subsequent successful esta- reduce future incursions but, blishment in new locations has taken particularly, to develop a set of tools place and continues to take place, add- that can be employed to manage esta- ing to the threats to forests across blished populations of the pests. In Europe. New threats are being many cases, there is a delay between recognised continually and can be illu- establishment and detection which strated by the two buprestid beetle inevitably reduces the likelihood of pests that have been the subject of the eradication, although this also depends Euphresco project PREPSYS on the population growth rates of the (www.forestresearch.gov.uk/prepsys). pests. Whilst direct intervention Emerald ash borer (EAB – Agrilus through application of insecticides and

6 fungicides is a potentially valuable Rhizophagus grandis in the UK and also component of a pest management tool in parts of and in the Georgian box, measures to attempt to restore the Republic (Fielding & Evans 1997). In natural balance between the pest other cases, natural suppression can be organism and its host tree and environ- encouraged by managing site ment are needed for longer-term popu- conditions and tree species mixtures to lation suppression towards an endemic improve the capacity of trees to defend state. Among these measures, natural against attacks by pests. Such measures enemies can play an important part, as require a good understanding of why evidenced by the successful mana- the pest is a problem and whether it is gement of the invasive great spruce possible to alter the key factors to bark beetle, Dendroctonus micans by return to an endemic state and to an the host-specific predatory beetle, acceptable damage threshold.

References Brockerhoff,E.G. & Liebhold,A.M. 2017 Ecology of forest insect invasions. Biol Invasions 19, 3141-3159. Fielding,N.J. & Evans,H.F. 1997 Biological control of Dendroctonus micans (Scolytidae) in . Biocontrol News and Information 18, 51-60. Herms,D.A. & McCullough,D.G. 2014 Emerald Ash Borer Invasion of North America: History, Biology, Ecology, Impacts, and Management. Ann. Rev. Entomol. 59, 13-30.

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Biological control options for invasive species using insect pathogens Jørgen Eilenberg Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C., [email protected]

Workshop abstract Upon arrival of invertebrate invasive spe- We have found insect pathogenic fungi cies, the management may include the occurring on a number of aphid species, use of insect pathogens. In my talk, I will including green spruce aphids. Further, introduce the different groups of insect we studied the prevalence of these fungi pathogens and their biological character- in green spruce aphids in Iceland and we istics, for example transmission, ability have compared the ITS 1 region of the to establish epidemics etc. Thereafter, I fungus Entomophthora planchoniana will discuss considerations to be made, found on different aphid species. The im- exemplified by the potential of using plications of our results will be discussed. fungal pathogens from Entomophtho- rales to control an invasive aphid species, green spruce aphid Elatobium abietinum.

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Invasive pests and diseases on birch in Anne Uimari Natural Resources Institute Finland, Juntintie 154, 77600 Suonenjoki, Finland [email protected]

Workshop Abstract are economically the most im- occur with species which are not harm- portant broadleaved trees in Finland. ful in their native environment and Silver birch (Betula pendula) grows in whose host species range and virulence the whole country excluding the north- can be affected by factors such as cli- ernmost Lapland, instead, downy birch mate. At the moment, insects dominate (Betula pubescens) manages also in the the group of known invasive spices North. The third native birch species in threatening Finnish birch production. Finland, dwarf birch (Betula nana), is a In 2015, Asian longhorned beetle (Ano- marshland shrub. Finnish forests of sil- plophora glabripennis) -affected birches ver and downy birches are planted with and goat willows were found in the nursery-produced genetically improved southern Finland. The beetle had ar- seedling material and the typical rota- rived with imported Asian stone mate- tion varies between 40 to 60 years. rial and was assumed to occupy the The Finnish nurseries and forests have area for several years. Although, the common pathogens and pests affect- pest was successfully eradicated, the in- ing birch growth and wood quality. cidence demonstrated the survival and However, large damage and destruc- breeding abilities of invasive species in tion have been avoided. In nurseries, very different climate compared to leaf and stem lesion-causing oomycete, their native environment. Global trade, Phytophthora cactorum, is the most seri- especially concerning plants and wood- ous problem against which fungicides connected materials, is an important are used. Occasionally, seedlings need pathway for invasive species and along to be treated with pesticides targeted that in 2017 two additional findings to thrips and aphids. In the forests, (one and one dead insect) of the birch rust and dieback by Melampsorid- Asian longhorned beetle were made in ium botulinum and Marssonina betulae, connection with stone import in south- respectively, are observed annually at ern Finland. some extent. Among pests, winter Another invasive insect encountered moth (Operophtera brumata) and north- occasionally in the South coast of Fin- ern (Operophtera fagata) land is gypsy moth (Lymantria dispar). can sometimes cause notable leaf loss The moth is native to South and Central and wood quality is commonly affected Europe but considered as one of the by birch stem miner, betulae. main defoliators of deciduous trees in Invasive pests and pathogens are a se- the northern hemisphere. Some other rious threat for birch production in Fin- birch-threatening invasive insects are land. They include species which are bronze birch borer (Agrilus anxius) not able to cause serious damage and de- yet present in Europe and citrus long- stroy and kill trees in large areas. In ad- horned beetle (Anoplophora chinensis) dition, unpredictable problems may observed in South Europe.

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Currently, the major group of invasive Altogether, Finnish birch forests con- pathogens threatening birch forests in taining only two Betula species which Finland is oomycetes of Phytophthora have evolved without the pressure of genus. Rhododentrons affected by Phy- highly destructive pests are seriously tophthora ramorum are annually found threatened by invasive forest pests af- in nurseries and plant stores. The first fecting broadleaved trees. occurrence of P. ramorum outside

nurseries was in 2018 on a Rhododen- dron plant grown in a park. The patho- gen was eradicated but because of in- ternational plant trade there is continu- ous threat of new incidences of P. ra- morum and other, partly unknown, birch-infecting Phytophthora species.

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