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  • The common mistletoe

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    1Miloň Dvořák, 2Magdalena Kacprzyk

    1Mendel University in Brno, Department of Forest Protection and Wildlife Management, Brno, Czechia

    2University of Agriculture in Krakow, Department of Forest Ecosystems Protection, Krakow, Poland

    Mendel University in Brno, Czech Republic | Study.eu University profile

      • General Information

        The common mistletoe (Viscum album L.) is an evergreen, perennial, epiphytic, hemiparasitic shrub that lives on a wide range of woody plant species. It is native to Europe and is a well-known pathogen, a pharmaceutical plant, and a symbol in mythology (Ochocka and Piotrowski 2002; Zuber 2004, Song et al. 2021).

      • Taxonomy

        Kingdom: Plantae, Phylum: Magnoliophyta, Class: Angiospermae, Category: Basal core eudicots, Order: Santalales, Family: Santalaceae, Genus: Viscum, Species: Viscum album L. (EPPO 2024).

        From the first half of the XVIII. century until modern times taxonomy of the mistletoe has been a subject of discussions and the existence of many species, subspecies or forms is not agreed generally (Zuber 2004, Melo et al. 2023). Most of the parasitic plants, including Viscum, have traditionally been included by botanists in the family Loranthaceae Juss. (Kuijt 1969, Visser 1981). However, the taxonomic position of mistletoe, as a result of all the knowledge about its origin, evolution, distribution and biology, has provoked conflicting opinions. Separation of the new family Viscaceae from the existing family Loranthaceae s. lato in the Santalales order seems appropriate because of the different evolutionary lineages and modes of parasitism on branches and other organs of host trees (Barlow 1964, Richardson 1978, Barlow and Martin 1984, Tachtadžjan 1987). Barlow (1964) also emphasizes that although the two families have independent origins, their ancestry should be sought in the Santalaceae family R. Br.

        According to the International Plant Name Index (IPNI 2024) and the World Flora Online (WFO 2025), following infraspecific taxa are defined: V. album subsp. abietis (Wiesb.) Abrom., V. album subsp. austriacum (Wiesb. Ex Dichtl) Vollm, V. album subsp. coloratum Kom., V. album subsp. creticum N.Böhling, Greuter, Raus, B.Snogerup, Snogerup et Zuber, V. album subsp. lutescens (Makino) Kitag., V. album subsp. meridianum (Danser) D.G.Long, V. album f. rubroaurantiacum (Makino) Kitag. The subspecies are often considered as synonyms to species names, e.g. Viscum album subsp. coloratum Kom. and V. album f. rubroaurantiacum (Makino) Kitag are treated by the Flora of China as a distinct species Viscum coloratum (Kom) Nakai. (Melo et al. 2023).

      • Local Names

        • (Common/European/white-berried) mistletoe (English)

        • Blondeau, bois/herbe de la Sainte Croix, bouchon, glu, gu, gui blanc/des feuillus, gui commun, gui de druides, herbe aux druides, verquet, vert de pommier (French)

        • Affolter, gewöhnliche mistle, Heiligeskreuzholz, Künst, Laubholzmistel, (weissberige) Mistel (German)

        • Almuérdago, arfuego, liga, liria, marojo, muérdago, tiña, visca, viscol (Spanish)

        • Jemioła pospolita (Polish)

        • Jmelí bílé (Czech)

        • Imelo biele (Slovak)

        • Fehér fagyöngy (Hungarian)

        • Vischio bianco, vischio, visco, vescovaggine, guatrice, pania, scoaggine (Italian)

        • Bедьмина метла (Russian)

        • ヤドリギ (Japanese)

        • Ιξός (Greek)

      • Host Tree

        V. album (L.) has been found parasitic on numerous taxons of trees. Barney et al. (1998) listed 452 taxons of woody plants. V. album subsp. album hosts broadleaved trees, namely maples (Acer spp., 25 hosts), alders (Alnus spp., 6 hosts), birches (Betula spp., 18 hosts), hornbeams (Carpinus spp., 3 hosts), Turkish hazel nuts (Corylus colurna), hop-hornbeams (Ostrya spp., 2 hosts), catalpas (Catalpa bignonioides), cornels (Cornus spp., 5 hosts), persimmons (Diospyros spp., 2 hosts), 15 hosts of the family Fabaceae, incl. black locust (Robinia pseudoacacia), chestnuts (Castanea sativa, C. crenata), beeches (Fagus sylvatica, F. orientalis), oaks (Quercus spp., 21 hosts), horse chestnuts and buckeyes (Aesculus spp., 10 hosts), walnuts and wingnuts (Juglans spp., Pterocarya spp., 11 hosts), hycories (Carya spp., 6 hosts), tulip trees (Liriodendron tulipifera), magnolias (Magnolia tripetala, M. virginiana), four species of the family Moraceae, gum trees (Eucalyptus globulus), dove tree (Davidia involucrate , incl. var. vilmoriniana), ashes (Fraxinus spp., 9 hosts), plane trees (Platanus orientalis, P. occidentalis), hawthorns (Crataegus spp.), quincies (Cydonia oblonga), apple trees (Malus spp.), photinias (Photinia serrulata), plum and cherry trees (Prunus spp.), pear trees (Pyrus spp.), whitebeams (Sorbus spp., 16 hosts), Amur cork tree (Phellodendron amurense), poplars (Populus spp.), willows (Salix spp.), tree of heaven (Ailanthus altissima), French tamarisk (Tamarix gallica), limes (Tilia spp., 13 hosts), hackberries (Celtis spp., 6 hosts), elms (Ulmus spp., 5 hosts), zelkovas (Zelkova carpinifolia) (Barney et al. 1998).

        Hosts of V. album subsp. abietis are mostly firs (Abies spp., 16 taxons), Japanese larch (Larix kaempferi), but also few hardwoods: silver and red maple (Acer saccharinum and A. rubrum) and goat willow (Salix caprea) (Barney et al. 1998).

        V. album subsp. austriacum is at most hosted by pines (Pinus spp., 17 hosts), but also by Nikko fir (Abies homolepis), cedars (Cedrus atlantica, C. libani), Japanese larch (Larix kaempferi), Norway spruce (Picea abies), Paraná pine (Araucaria angustifolia) and European yew (Taxus baccata). From hardwoods it can be hosted by balsamic poplar (Populus balsamifera) and goat willow (Salix caprea) (Barney et al. 1998).

        V. album subsp. creticum Böhling is recorded on Calabrian pine (Pinus brutia), while V. album subsp. meridianum (Danser) D.G.Long grows on Monbeig’s hornbeam (Carpinus monbeigiana), common walnut (Juglans regia), Chinese cherry (Prunus pseudocerasus), large-leaved rowan Sorbus megalocarpa, and maples (Acer spp.) (Qiu and Gilbert 2003).

      • Signs and Symptoms

        A tree infected by mistletoe is detectable at first sight by mostly globose perennial evergreen shrub which may reach up to 1.5 m with dichasial branching pattern. Leaves are opposite, sessile, obovate-oblong, obtuse, leathery, yellowish-green, with almost parallel veins, ca. 2 - 8 cm long and up to 4.3 cm wide, varying in size, depending on the subspecies (Zuber 2004). V. album is dioecious plant and reproduces sexually. The flowers are small (a diameter of 2-3 mm), sessile and yellowish-green, formed usually in triads with one terminal and two lateral flowers. Mistletoe blooms in March-April, around the age of 5 (Tubeuf 1923; Wangerin 1937). Three, usually white or sometimes slightly yellow, fruits called “pseudoberries” are formed in a crotch on a shoot apex from the previous year. The fruits are 6 – 10 mm in diameter, globose or pyriform, but in some species egg-shaped. The inner mass of the fruits (mesocarp) consists of mucilaginous substance (viscin) in two layers. The outer cellulosic layer is digestable, while the inner one containing pectin is not. In the centre of the fruit there are 1 - 4 “seeds” (chlorophyllous embryos enclosed in thin endocarps) (Zuber 2004).

        Viscum album ssp. austriacum bushes in the crown of Scots pine (Pinus sylvestris L.) in the north east Poland (made available by Sławno Forest -District)

        Branches and stems infected by V. album are penetrated by haustoria and cortical strands. Haustoria rapidly grow to reach cambium to absorb water and mineral salts, embedded in host xylem tissue. Cortical strands grow through parenchymatous and phloem tissue to provide the lateral spread of the parasite (Zuber 2004).

        The maximum age of mistletoe is about 27-30 years (Wangerin 1937; Nierhaus-Wunderwald and Lawrenz 1997).

        Viscum album ssp. austriacum bushes in the crown of Scots pine (Pinus sylvestris L.) in the north east Poland (made available by Sławno Forest -District)

      • Discovery and History

        Already Hippocrates (460 – 377 BC) recommended mistletoe to treat diseases in the spleen and complaints associated with menstruation (Bussing 2000). However, proofs of its existence are much older. Representatives of the Viscaceae found on the European continent originated in the southern hemisphere, during the Late Cretaceous period, when the southern continents constituted the entire landmass of Gondwana (Barlow 1988). Representatives of the Viscaceae family owe their current range to the gradual migration of tree host species along the continent from Asia to Europe (Barlow 1987). In Central Europe, the presence of Viscum was found in the younger stages of the Neogene in deciduous and mixed forests, on trees of the genera: Acer L., Betula L., Tilia L., and Ulmus L.. (Stuchlik et al. 1990). During the Ice Age, mistletoe was found in Europe in the Mediterranean basin, and after the glacier receded, it migrated north with its hosts (Tubeuf 1923). In Holocene sediments, Viscum pollen has been found in southwestern Jutland and the Netherlands (Iversen 1960), while in Denmark, Viscum pollen has been discovered in boreal, Atlantic and subboreal sediments (Godwin 1975). Fossil evidence shows that during postglacial warmth period Viscum was distributed in most provinces of northern Sweden.

        Into the North America (near Sebastopol, California) the European mistletoe was introduced around 1900 by horticulturist Luther Burbank (Scharpf and Mc Cartney 1975; Scharpf and Hawksworth 1976; Hawksworth et al. 1991). Although Viscum here is characterized by its high ability to take over both native and non-native trees (Mc Cartney et al. 1973; Hawksworth et al. 1991, Shaw and Lee 2020) the plant did not spread massively (Zuber 2004). In 1988, the European mistletoe was also found on Malus Mill. in Canada (Dorworth 1989).

      • Distribution

        The current distribution according to EPPO Global Database (EPPO 2024) is practically throughout whole Europe (except Ireland, Finland and northern Russia) and Mediterranean (except southeast), Caucasus, Western Asia (Iran to Afghanistan), Himalayas, Indochina (Myanmar, Vietnam), China (including Tibet), Canada (British Columbia) and USA (California). Zuber (2004) described the geographical limits in longitude and latitude: 10° W to 80°E (except of V. album subsp. coloratum) and 60° N to 35° S. Generally, it is adapted to temperate climate, outside of extreme continental regions.

        In vertical profile, V. album grows in colline and submontane regions not above 1000 m altitude, however, in the south (Spain) it occurs in higher altitudes (Zuber 2004; Zamora and Mellado 2019).

        Expansion of the common mistletoe in Europe, as o consequences of ongoing climate warming, resulted changes in the plant distribution, a good example of which are the Swiss Alps where the upper limit of the pine mistletoe occurrence has shifted by 200 m (Dobbertin et al. 2005). When estimate the dynamics of mistletoe range changes based on temperature and host availability (Walas et al. 2022), it is quite likely that the area of the current range of mistletoe may shift to the northeast, while in the mountainous areas of Europe to higher altitudes. On the other hand, the withdrawal of genetically distinct mistletoe populations from southern Europe can be expected.

      • Dissemination and Vectors

        Mistletoe dispersal is heavily reliant on birds, which eat the pseudoberries and inadvertently help the plant establish itself on new trees (Watson 2001). The pseudoberries are dispersed from February to May when songbirds fly back northwards (Wangerin 1937). Most important birds for mistletoe dispersal are the mistle thrush (Turdus viscivorus), fieldfare (Turdus pilaris), waxwing (Bombycilla garrula) and blackcap (Sylvia atricapilla). While the first three feed on the whole berry and excrete the “seed” without the berry skin, the blackcap feeds only on the skin of the berry and leaves the “seed” on a shoot nearby the mistletoe shrub. While sitting with the berry on a branch, it maintains the berry against the bark with its leg. It withdraws and swallows the external part of the pulp adhering to the teguments (Zuber 2004).

        The approximate distance of dispersal by thrushes is 17 km and it is dependent on the length of the intestinal passage. The faster the digestion is, the shorter distance the seed achieves (von Tubeuf 1923). The long distance dispersal has to take place in another way, such as being stuck on the plumage or bill of birds and stripped off somewhere else (Wangerin 1937)

      • Regulations and status

        Mistletoe is listed in the Composite List of Weeds of the Weed Science Society of America (EPPO 2024). Viscum album L. is protected by law in northern European countries. In Sweden, legal protection of mistletoe was introduced as early as 1910, and in Norway in 1956 (Wallden 1961). Under state protection, mistletoe is also found in Latvia, where it is treated as a relict of the post-glacial Atlantic period (Riekstinš 1980).

      • Impact

        Ecological Impacts

        As long as V. album L. is not present in large numbers on trees, it does not poses a lethal threat to them (Glatzel and Geils 2009. However, in the face of climate change, leading to more frequent droughts, weakening host trees and consequently increasing the role of mistletoe, which, by reducing the availability of water and nutrients (Sanguesa-Barreda et al. 2012, Mutlu et al. 2017) significantly worsens the condition of the trees during the dry summer seasons and alone or in combination with other factors (pests, diseases) increases their mortality (Iszkuło et al. 2020). This phenomenon is observed in recent years in eastern and central Europe (Kollas et al. 2018; Lech et al. 2019; Szmidla et al. 2019).

        The presence of mistletoe in tree crowns affects them either directly, by shortening the life of the host plant, or indirectly, by affecting traits related to the habitat (for example, the availability of food resources). Due to the mistletoe's relatively long life span, its dependence on the host lasts for many years and can be intensified by the systematic appearance of successive individuals of the parasite on the tree (Zuber 2004; Mellado and Zamora 2017).

        V. album impacts negatively its host depleting water with mineral nutrients and decreasing the photosynthetic rate of the tree (Glatzel i Geils 2009; Zweifel et al. 2012). During periods of severe drought, the stomata on the tree's leaves are closed, while the gas exchange intensity of mistletoe remains very high (Zweifel et al. 2012). This increases the host's water deficit and can contribute to its weakening (Schulze and Ehleringer 1984; Zweifel et al. 2012). Under drought conditions, the risk of death of mistletoe-infested individuals is four times higher, compared to trees free of the parasite (Geils et al. 2002). As negative effects of mistletoe infestation of trees reduction or disappearance of fruiting, defoliation, and decrease in tree growth is often observed (Becker 1986; Sönmez 2014; Iszkuło et al. 2020). In addition, wounding the branches and stems by its endophytic structures facilitates infection by other pathogens, resulting in co-infections, especially with fungi (Geils et al. 2002; Noetzli et al. 2003; Zuber 2004; Mathiasen et al. 2008). The effects of mistletoe infestation on trees are not only seen in individual specimens of the host plant, as this is a species that can affect the entire ecosystem, such as species composition and stand structure (Watson 2009; March and Watson 2010; Mellado and Zamora 2017). 

        However, shrubs of mistletoe serve as a specific ecologic niche. It is a habitat for specific communities of arthropods, e. g. Cacopsylla visci, Pinalitus viscicola, Anthocoris visci (Lázaro-González et al. 2017). 60 families across 16 orders of birds are reported to nest in the shrubs of mistletoe worldwide (Cooney et al. 2006). Infections of trees by mistletoe, through defoliation of crowns, contributes to changes in light conditions, initiating the emergence of new plant species, while falling mistletoe seeds, together with the excrement of birds that spread them, increase soil fertility. In addition, reducing the content of certain substances in the needles of mistletoe-infested pines can have a positive effect on reducing the development and survival of foliar pests (Lázaro-Gonzalez et al. 2019).

        In nature conservation mistletoe plays the role of a phytoindicator of contamination of the natural environment with heavy metals (Nováček and Teterová 1987; Patykowski and Kołodziejek 2016).

        Economic Impacts

        The negative economic impact connected with the loss of infested trees is evident. However, mistletoe has been a profitable good due to few reasons. It is a pharmaceutical plant, it is shrouded in legends and it is decorative.

        Already Hippocrates (460–377 BC) recommended the European mistletoe to treat diseases in the spleen and complaints associated with menstruation (Bussing 2000). In the early 18th Century, Sir John Colbatch (1719-20) stated that mistletoe was a "most wonderful specific remedy for the cure of convulsive distempers." He referred to V. album, which has since left the realm of witchcraft, herbalism, and quackery to become an accepted pharmaceutical plant (Gill and Hawksworth 1961). Extracts of V. album demonstrated hypotensive, anticancer, antimicrobial, analgesic and anti-inflammatory capabilities, among other biological activities (Luther and Becker 1986; Vicaş et al. 2011; Szurpnicka et al. 2020, Kieszken et al. 2022). They are widely used as complementary and alternative medicines for the treatment of various neurological disorders. Lectins, viscotoxins, lignans, amines, amino  acids,  alkaloids,  polyphenols, phenolic acids, polysaccharides and terpenoids are the main active compounds (Melo et al. 2023, Vicaş  et al. 2024).

        Mistletoe has been mentioned even as food for human, e.g. Australien tribes. In Europe it was used as nutritious fodder for livestock (Gill and Hawksworth 1961, Barlow 1987; Akeret et al. 2001; Hejcman et al. 2013; Kühn et al. 2013). Until the first half of the 19th century, Viscum spp. fruits were used to make a bird stick in Africa and Europe. as well as to reduce populations of harmful insects attacking young vines (Jabłonski and Szmidla 2022). In folk medicine, the Celts used mistletoe to treat various ailments as early as ancient times.   

        It seems also interesting to use chemical compounds derived from the common mistletoe as an alternative methods of soil nematode control based on the toxical action of the plant extracts. Maher et al. (2021) confirmed the bioactive properties of V. album against root-knot nematode Meloidogyne incognita.

        Collected shrubs of V. album are commonly commercialized in Christmas markets for decorative purposes.

        Social Impacts

        The most well-known social impact of mistletoe is its association with Christmas and the tradition of kissing under the mistletoe. This custom dates back to the 18th and 19th centuries. It is considered a symbol of peace, goodwill, and fertility. People often hang mistletoe in doorways during the holiday season, and the act of kissing under it has become a playful social ritual. Mistletoe is often believed to bring good luck. In France mistletoe was often given as a Porte Bonheur – a gift for luck for the New Year. Furthermore, in Britain it was associated with peace at one time, though it has become eclipsed by the kissing custom (Briggs 2022).

        Mistletoe is very popular especially in regions with its high occurrence and more intensive utilization. For example mistletoe enthusiasts close to Herefordshire in Britain established annual ceremony to crown a Mistletoe Queen and have chosen 1st December as the National Mistletoe Day (Briggs 2022).

      • Management

        Detection

        To detect the shrubs and haustoria by naked eye is easy due to specific morphology of the plant when it is approachable. Pernar et al. (2007) developed an efficient method of mistletoe detection by remote sensing. They achieved overall accuracy in the range of 62.50 to 70.56% using a combination of unsupervised and supervised classification of imagery classification data acquired from three visible bands combined with one near infra-red band. The use of high-resolution satellite or aerial imagery in detecting mistletoe in forests under European conditions has so far been tested only in France and Croatia (Iszkuło et al. 2020). In recent years, there have been research results on unmanned aerial platforms in remote sensing, such as studies on mistletoe attacking eucalyptus trees in Australia (Maes et al. 2018), or comparisons of data acquired with their help to satellite imagery (Dash et al. 2018). According to Ančić et al. (2014), detection of trees infection by the European mistletoe is possible and requires further research, it is also cost-effective and should be used on a wider scale especially in management and planning in forest ecosystems.

        Preventive measures and suppression measures

        To prevent mistletoe infestation in urban areas it is possible to plant resistant or tolerant cultivars of trees. Investigation of less susceptible individuals revealed anatomic and biochemical markers of higher levels of resistance. For example, thick cortex, high density of polyphenol-containing cells, thick first layer of fibers, thick collenchyma or prompt flavonoid synthesis are favoring the host tree (El Hariri et al. 1991).

        Zuber (2004) concluded that there is no generally efficient control method of mistletoe apart of mechanical removal of the shrubs, invaded branches or whole trees. However, in smaller areas like urban parks he founded this method appropriate. 

        In North America, there have been attempts to chemically control mistletoe (Livingston et al. 1985, Baker et al. 1989, Geils et al. 2002, Zuber 2004; Hoyt et al. 2017). Some systemic herbicides proved to be able to kill V. album with only a little damage of the host. Phenoxybutyric (2,4-MCPB), 2,4-dichlorophenoxyacetic acid (2,4-D), trichlorophenoxyacetic acid (2,4,5-T), di-chloro ethane and glyphosates were tested, but showed maximum effect only 4-6 months after treatment, furthermore, the endophytic system of the mistletoe was barely affected (Adams et al. 1993, Geils et al. 2002, Zuber 2004). Interesting results were received with application of the plant growth regulators such as ethephon ((2-chloroethyl)-phosphonic acid). Experiments of Adams et al. (1993) did not turn out promising. Ethephon caused fast abscission of mistletoe leaves and desintegration of mistletoe shrubs, but did not affect the endophytic system. Therefore, mistletoe regenerated during the following season. On the other hand, Rozsypálek et al. (2022) achieved considerable improvement of ethephon efficiency delimiting the conditions of its application. 60 – 70% of haustoria were killed after ethephon spraying during deep dormancy of the host trees, i.e. in a period starting 15 days after total leave fall and finishing at least 60 days before budding. Furthermore, ethephon must be sprayed on dry leaves, from -5 to +10 °C. Application is significantly less effective on heavily infected trees where the mistletoe predominates the foliage of the tree (Rozsypálek et al. 2022). The use of chemicals to control mistletoe is often questioned (Adams et al. 1993). Thus the key is to minimize the negative effects of the herbicide on trees and other environmental elements (Wood and Reilly 2004). Experiments with biocontrol of mistletoe did not bring considerable outcomes yet, because the range of pathogens and pests of mistletoe is not very wide due to its effective defense system. Kotan et al. (2013) tested 48 isolates of fungi and 193 bacterial strains isolated from declining mistletoe shrubs to reveal their potential as biological control agents. He pointed out fungal isolates of Alternaria alternata and Acremonium kiliense which caused dead of the artificially infected shrubs. Recently, a new fungus (Septoria krystynae Ruszk.-Mich.) was also discovered and described, causing a disease known as septoria in mistletoe (Pawłowicz et al. 2024).

        Despite the existence of pathogens and insect pests that feed on mistletoe, however, none of them currently significantly affect the reduction of V. album, either in Europe (Zuber 2004) or in North America (Geils et al. 2002), and the only real threat to mistletoe is humans (Reid et al. 1995). The most effective and widely used way to reduce mistletoe on trees is to eradicate infested parts or entire specimens (Hawksworth 1983). However, in forestry, removal of individual branches is very difficult to carry out. Moreover, mistletoe has the ability to form dehiscent shoots from haustoria, i.e. roots that are hidden in the host tissue, making it difficult to combat the semiparasite (Zuber 2004). Removal of entire trees seems to be an effective solution. However, in the case of mistletoe, the feasibility of this type of treatment should be assessed each time, since usually more than one tree becomes infected by the semiparasite (Sanguesa-Barreda et al. 2012; Durand-Gillmann et al. 2014; Pilichowski et al. 2018), which can affect the difficulty of performing the treatment. In addition, decrease in tree cover improves conditions for the spread of mistletoe (Geils et al. 2002; Zuber 2004; Hoyt et al. 2017). The issue of effectively reducing the occurrence of mistletoe in forests is therefore still unresolved.

        Respond & Control

        To control the amount of mistletoe on trees, observe the rate and extent of the plant spread, different inventory methods and approaches, based on the use of traditional techniques, including crown observation and estimating the intensity of the occurrence of the pathogen are used in forest ecosystems. One of the more frequently worldwide used is the six-grade mistletoe rating scale (6-class dwarf mistletoe rating system (DMR)), proposed by Hawksworth (1977). In the method an observer visually dividing the tree's crown into three parts and separately assessing each of them for the degree of mistletoe infestation. This method allows to calculate the intensity of stand infection by Viscum spp. on the basis of the arithmetic mean DMR for the tested trees (Parker and Mathiasen 2004). An alternative to the 6-point Hawksworth scale is Broom volume rating (BVR) method, that in Tinnin (1998) opinion is simpler and faster to use compared to the previous one. Similarly to the Hawksworth method, the tree crown is divided into three parts (upper, middle and lower), where branches without infection and infected branches are counted in each of them. Mistletoe and co-occurring black broom are taken into account.

        A four-class system proposed by (Barbu 2009), after assigning inventoried trees, on the basis of the intensity of mistletoe infestation and parts of the tree, to a particular class, includes measurements of the breast height, the height of the trees and their annual growth.

        The degree of trees infestation by Viscum spp., using the total broom volume rating (TBV) method was proposed by Parker (2001). Unlike previous methods, it assumes the evaluation of the degree of mistletoe infestation not only the crown of the tree, but also its entire heigh (Parker 2001; Parker and Mathiasen 2004). Live crown volume percent-age (PCB) is an estimation method for assessing live branch infested by mistletoe, in which grades determine the percentage of mistletoe in a tree's crown with an accuracy of 10% (Parker and Mathiasen 2004). Because the TVB and PCB methods rely on percentage estimates of mistletoe infestation on trees, posing a risk of significant over- or underestimation of infestation, there are some limitations in practical application, as evidenced by the lack of many examples of the use of these methods.

        The needle weighting method, aimed to determine the biomass of mistletoe and needles from mistletoe-infected branches for comparison with the biomass of branches uninfected (Bilgili et al. 2014) can be used to model the effects of mistletoe on the host, which can contribute to its control.

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        13. Bilgili E, Eroglu M, Coskuner KA, Baysal I (2014) Determination of biomass of European pine mistletoe (Viscum album ssp. Austriacum (Wiesb.) Vollman) on infected Scots pine (Pinus sylvestris L.) branches. Türkiye II. Orman Entomolojisi ve Patolojisi Sempozyumu. 7−9.04.2014

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