Needle and shoot diseases of pine - Fact sheet - DORA 4RI
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ISSN 2624-8077
Fact sheet Swiss Federal Institute WSL
CH-8903 Birmensdorf
© WSL Birmensdorf, 2022
70
WSL, Zürcherstrasse 111 April
CH-8903 Birmensdorf
www.wsl.ch/publications 2022
Needle and shoot diseases of pine
Vivanne Dubach, Valentin Queloz and Sophie Stroheker
Pine trees are an integral part of the for-
est landscape across Switzerland (see
Fig. 4). In recent years, they have come
under increasing pressure, not least due
to new fungal diseases that have been
introduced from abroad. Needle and
shoot diseases play a major role for pine
health. The Swiss Forest Protection
Group has been documenting diseases
affecting Swiss tree species since 1984.
When the appearance (habitus) of an
infested pine changes, the tree attracts
attention. Needle and shoot diseases are
clearly visible and thus easily change the
appearance of the tree. Pines in particu-
lar are susceptible to many such dis-
eases, also in comparison with other
conifers such as Norway spruce (Picea
abies) and silver fir (Abies alba). This is
also reflected by the comparatively high
level of attention devoted to the pine
tree both in research and in the advisory
activities of the Swiss Forest Protection
Group.
Needle diseases not only change the
appearance of the tree, however. They
can also weaken the tree, and thus in-
crease its susceptibility to other biotic
and abiotic influences. Conversely, biotic
and abiotic stress factors make a tree
susceptible to infection with needle dis-
ease: the weaker the tree, the more eas-
ily additional infections occur. Examples
of abiotic stress factors include drought,
hail or sudden waterlogging. An exam-
ple of a biotic damaging influence is the
infection with a root pathogen such as
the honey fungi Armillaria, to which
Scots pine (Pinus sylvestris) is particularly
susceptible (Nierhaus-Wunderwald et al.
2012).
Fig. 1. Mature Scots pine (Pinus sylvestris) with a healthy appearance. Drawing: Vivanne Dubach.
Significance of needle and For some years now, pines in Switzer- goes by. As it is not a disease, it does not
shoot diseases in pines land have been increasingly affected by appear in the list. However, it is described
two “new” needle diseases: the red further on in the leaflet.
Pines make up about 4.7 % of trees in band needle blight, caused by the fungi
the Swiss forest (stem count Swiss Dothistroma septosporum and Dothis
National Forest Inventory (NFI)4; Abegg troma pini, and the brown spot needle The most common needle
et al. 2020). According to the fourth blight, caused by Lecanosticta acicola. and shoot diseases of pines
Swiss National Forest Inventory, the As both diseases can cause great dam- in Switzerland
Scots pine (Pinus sylvestris) is the most age to pines, they are classified as “par-
common forest species, accounting for ticularly dangerous organisms” (“BgSO” Records kept by the Swiss Forest Protec-
2.3 % of the total forest area in Switzer- [Swiss plant protection ordinance]). tion Group since 1984 show that the
land, followed by the Swiss mountain Since 2020, they have been considered Lophodermium pine needle cast dis-
pine (Pinus mugo, 1.2 %), the stone pine to be “regulated non-quarantine organ- eases (L. seditiosum and L. pinastri) are
(Pinus cembra, 1.2 %), the black pine isms” (“GNQO”; PGesV-WBF-UVEK, SR among the most frequently recorded
(Pinus nigra, 0.04 %), and other, non- 916.201 [under the Swiss plant protec- needle and shoot diseases (Fig. 2a).
native pine species (0.01 %). tion ordinance]). To keep an eye on the Three other fungi are also very strongly
The pine is a pioneer tree species. At damage potential and spread of these represented in the database. The path-
lower altitudes, it usually disappears newcomers, the Swiss Forest Protection ogens of brown spot needle blight (Le
from the stand as the forest develops if Group has been monitoring the diseases canosticta acicola) and red band needle
it is not silviculturally promoted, due to since 2009. In the course of these activ- blight (Dothistroma spp.) have become
its need for light. Pines therefore often ities, numerous other needle diseases the focus of increasing attention since
occur in mixed stands, or they are dis- have been detected. 2009 because of their potential to cause
placed by competition on to dry, shallow This leaflet draws on the wealth of in- damage (Dubach et al. 2018). Selective
or very moist extreme sites (ETH 1995). formation gathered by the Swiss Forest data has been greatly improved as a
Scots pine, mountain pine and stone Protection Group since 1984, and pres result, as shown in the comparison of
pine in particular are able to survive on ents the pathogens of the most common data since and before 2009 (Fig. 2b).
difficult sites. In some areas, pines also needle and shoot diseases of pine trees This comparison shows that, after the
form whole stands (e. g. the Swiss stone in Switzerland (Tab. 1). Physiological nee- relevant initial findings, there were very
pine forests of the subalpine vegetation dle blight (also known as physiological few reports of red band disease and
zone; the Swiss mountain pines of up- needle cast), which is often confused brown spot needle blight. It was not
land moors), and are thus essential for with disease and therefore reported to until the Swiss Forest Protection Group
forest functions to be delivered (e. g. the Swiss Forest Protection Group, is a began their active monitoring of the
protection against rockfall and soil ero- natural process of needle ageing – a pro- diseases that the data situation and thus
sion in particular). cess undergone by all needles as time knowledge about these two dangerous
Tab. 1. Overview of the most significant needle and shoot diseases of pines in Switzerland.
Name (scientific) Synonyms Name (english) Most frequently
affected tree organ
Cenangium ferruginosum C. abietis Cenangium dieback, shoot dieback of pine Shoot
Cronartium pini C. flaccidum, C. asclepiadeum Pine blister rust, stem rust of pine Shoot
Cyclaneusma minus Naemacyclus minor Cyclaneusma needle cast, Needle
Naemacyclus needle cast
Coleosporium spp. Coleosporium pine needle rust Needle
Diplodia sapinea Sphaeropsis sapinea Diplodia tip/shoot blight of pine Shoot
Dothistroma spp. for D. septosporum: Scirrhia pini Red band needle blight Needle
(D. septosporum, D. pini)
Gremmeniella abietina Ascocalyx abietina, Scleroderris abietina Scleroderris dieback / Brunchorstia dieback Needle and shoot
Herpotrichia pinetorum H. juniperi Black snow mould, brown felt blight Needle and shoot
Lecanosticta acicola Brown spot needle blight Needle
Lophodermella conjuncta Swedish pine needle cast Needle
Lophodermella sulcigena Swedish pine needle cast Needle
Lophodermium pinastri Lophodermium needle cast Needle
Lophodermium seditiosum Lophodermium needle cast Needle
Gremmenia infestans Phacidium infestans Snow blight, Swiss stone pine snow fungus Needle and shoot
Sydowia polyspora Sclerophoma pithyophila, Phoma pithyophila, Sydowia dieback of pine Needle, shoot and
Dothidea polyspora, Hormonema dematioides wood
2 WSL Fact sheet 70 (2022)
a) Database records 1984−2020
Coleosporium spp. Survey
Sydowia polyspora Consultation
Lophodermella spp.
Cyclaneusma minus
Herpotrichia pinetorum
Cronartium pini
Gremmenia infestans
Gremmeniella abietina
Cenangium ferruginosum
Physiological needle blight
Diplodia sapinea
Dothistroma spp.
Lecanosticta acicola
Lophodermium spp.
0 100 Number 200 300
b) Database records 1984−2008
Lophodermella spp.
Physiological needle blight
Sydowia polyspora
Coleosporium spp.
Cyclaneusma minus
Dothistroma spp.
Herpotrichia pinetorum
Lecanosticta acicola
Cronartium pini
Gremmenia infestans
Cenangium ferruginosum
Gremmeniella abietina
Diplodia sapinea
Lophodermium spp.
0 100 200 300
Number
Fig. 2. Evaluation of the Swiss Forest Protection Group database (1984–2020) on needle and shoot diseases of pine. a) Period from 1984 to 2020. b) Period
from 1984 to 2008. All categories of native pine species were considered: Scots pine (Pinus sylvestris), mountain pine (P. mugo), black pine (P. nigra) and
stone pine (P. cembra) as well as pines in general (if no more precise information on the tree species could be provided). Consultancy: all findings that were
entered by employees of the Swiss Forest Protection Group either in consultancy or in the course of their own observations. Survey: Data from the annual
Swiss forest protection survey as well as summarised spontaneous reports from the forestry and green sectors.
Stone pine (n = 72) Mountain pine (n = 552) Black pine (n = 206) Scots pine (n = 156)
Cenangium ferruginosum
Coleosporium spp.
Cronartium pini
Cyclaneusma minus
Diplodia sapinea
Dothistroma spp.
Gremmeniella abietina
Herpotrichia pinetorum
Lecanosticta acicola
Lophodermella spp.
Lophodermium spp.
Phacidium infestans
Physiological needle blight
Sydowia polyspora
0 20 40 60 80 0 20 40 60 80 0 20 40 60 80 0 20 40 60 80
Percent Percent Percent Percent
Fig. 3. Distribution of the most frequently observed needle and shoot diseases among the different pine species. Only the pathogens described in this
leaflet were considered for these evaluations. Data for which the pine species was not precisely specified as well as data from the survey were not
included in this analysis. n = number of database entries.
WSL Fact sheet 70 (2022) 3
fungi improved. As a result of this moni needles die after a few years. Physio common condition observed was physio
toring, the detection rate of pine shoot logical needle blight (PNB) in principle logical needle blight.
dieback (Diplodia sapinea) can also be thus affects all pines. Damage to Swiss There are clear differences between
seen to have increased. Its striking symp- stone pine caused by the red band need black pine and the other pine species
toms have often been observed in the le blight (Dothistroma spp.) originates in (Fig. 3, black pine); in black pine, dam-
course of the active searches. urban areas. As stone pines have rela- age caused by Diplodia shoot dieback
tively thin needles, symptoms of red (D. sapinea) dominates. Red band need
band needle blight are sometimes more le blight is the second most common
The most common fungi on the difficult to see. It is thus more likely to disease affecting this species, but occurs
different species of pine be detected in gardens than in the for- much less frequently. All other patho-
Cenangium shoot dieback (C. ferrugino est. Brown spot needle blight (Lecanos gens described here are responsible for
sum) and Scleroderris shoot dieback, ticta acicola) has not yet been found on only a small proportion of the damage
also known as Scleroderris canker Swiss stone pine. Of all the pine species reported on black pine.
(Gremmeniella abietina), were the dis- described here, mountain pine is most On the most common Swiss pine spe-
eases most frequently found on needles affected by brown spot needle blight cies, the Scots pine, red band needle
and shoots of the stone pine (Fig. 3, (Fig. 3, mountain pine). On mountain blight is the most frequently recorded
Swiss stone pine). Also common were pine, these two imported diseases, the cause of damage, closely followed by
snow blight (Phacidium infestans) and redband needle blight and brown spot Diplodia shoot dieback (Fig. 3, Scots
physiological needle blight (natural age- needle blight, together account for pine). Cenangium dieback also occurs
ing of the needles, not a fungal disease). more than 75 % of the observed infest frequently on Scots pine, as does physio
The latter is not surprising, since all ations of mountain pine. The third most logical needle blight.
How to identify the most common pines in Switzerland
Scots pine (Pinus sylvestris) Scots pine
– Distribution: from lowlands up to 1800 m,
sometimes up to 2200 m a. s. l. (Engadine, Mountain pine
Valais)
– Tree height rarely exceeds 40 m Scots pine
Mountain pine
– Maximum age: around 600 years
– Bark: orange-brown in upper crown, peels Scots pine
off in thin flakes; darker on lower trunk, Mountain pine
with fissures and scaly plates Swiss stone pine
– Needles: 2 per short shoot; 4–7 cm; life
span of 1–8 years, depending on the site Mountain pine
Swiss stone pine
– Cones: curved downwards in the first year;
mature cones egg-shaped to conical,
3–7 cm long, pendulous
Fig. 4. Modelled distribution areas of Swiss pine species from the MoGLi project (Modelling of shrub
species LFI), based on records of the National Forest Inventory LFI (Wüest et al. 2021). Data were
Mountain pine (Pinus mugo) pooled at the community level (B. A. Augustinus 2021). Black pine is not part of this dataset, as it
– Distribution: P. mugo ssp. uncinata from hardly occurs in the forest.
600 to 2350 m a. s. l.; P. mugo ssp. mugo
up to 2400 m a. s. l.
– Tree height P. mugo ssp. uncinata up to 25 m Black pine (Pinus nigra) Swiss stone pine (Pinus cembra)
– Maximum age: P. mugo ssp. uncinata – Distribution: From lowlands up to 2000 m – Distribution: from lowlands up to 2600 m
around 300 years, P. mugo ssp. mugo around a. s. l. a. s. l.
100 years – Tree height up to 50 m – Tree height up to 25 m
– Bark: greyish-brown, initially peels off in – Maximum age around 500 years – Maximum age: around 600 years
flakes, then develops fissures and coarser – Bark: light to dark greyish-brown, with – Needles: 5 per short shoot; 5–12 cm long,
scales same colour reaching into crown; develops triangular; life span of 3–6 years; fascicle
– Needles: 2 per short shoot; 3–4 cm long, fissures and coarse scaly plates with age sheath falls off in the first year
rarely up to 8 cm; life span of 5–10 years, – Needles: 2 per short shoot; 8–16 cm long; – Cones: have short-stalks, obliquely upright
depending on the site have a life span of 4–8 years, depending on or protruding; purple when young; ovoid,
– Cones: not turned downwards in the first the site; they fall off with the fascicle sheath 6–8 cm long; fall off with the ripe seeds
year; mature cones egg-shaped to conical, – Cones: have very short stalks; young cones
2–7 cm long, almost sessile, inclined or obliquely upright, more mature ones usual
diverging horizontally from the branch, ly at right-angles to branch; egg-shaped to
remain on the tree for a long time conical, 4–10 cm long
4 WSL Fact sheet 70 (2022)
Short portraits of needle and shoot diseases of pines
Lophodermium needle cast
The needle cast disease caused by the fungus Lo needle (Behnke-Borowczyk et al. 2019). It is a
phodermium seditiosum results in a mass, prema- significant coloniser of dying needles, contributing
ture loss of needles and short shoots in pines. as a saprobiont to needle decomposition. The
Infected needles are shed until early summer, fruiting bodies are very similar to those of L. sedi
while infected short shoots are shed throughout tiosum. In L. pinastri, however, the fissure is often
the year. These symptoms are not to be confused reddish and there are black demarcation lines vis-
with needle loss due to physiological needle ible on the needle.
blight. In summer, the sexual fruiting bodies of Nowadays, a distinction is made between three
L. seditiosum form in the litter or on needles on different groups of L. pinastri (Reignoux et al.
the tree (needle on the left in the picture). They 2014), which are pathogenic to varying degrees.
are about 1 mm long, black and oval, and have Since L. pinastri is one of the fungi most fre-
a longitudinal fissure with a greenish shimmer. quently found in pine needles, while L. seditiosum
The fissure opens when moist to release spores. is not always present (Patejuk et al. 2021; Lazarevic
The spores then infect the youngest needles. The and Menkis 2020), it is suspected that L. pinastri
higher the humidity in the summer months, the occupies the same infection sites and thus partially
wetter and warmer the autumn and the milder prevents colonisation by L. seditiosum. While L.
the winter, the better L. seditiosum develops seditiosum seems to prefer the Scots pine in Switz
(Behnke-Borowczyk et al. 2019). erland, L. pinastri is found most frequently on
Lophodermium pinastri (needle on the right in Swiss stone pine.
the picture) is considered to be a fairly harmless There are no effective countermeasures in Switz
endophyte, whereas L. seditiosum can cause prob- erland, as the application of chemical agents such
1 cm lems, especially in tree nurseries. Both species can as fungicides is prohibited in the forest. In gardens,
occur latently as endophytes in the needle for a it is possible to try to rake up the majority of the
long time without causing symptoms. The occur- needles regularly and thus to reduce the risk of
rence of L. pinastri increases with the age of the infection.
Brown spot needle blight
The brown spot needle blight (Lecanosticta aci water droplets that carry spores from infected
cola), a non-native pathogen, was first observed needles to other trees. The fungus thrives particu-
in Switzerland in the canton of Zurich in 1995 and larly well at temperatures of 17–22 °C.
first detected in the forest in 2016. Mountain pine (P. mugo, 83 %) is particularly
On green needles that are one or more years of susceptible to this fungus. Other pine species are
age, yellow to brown spots develop in spring, also affected, but to a much lesser degree: Scots
usual ly with a yellow edge. They are initially pine (P. sylvestris) 7.5 %; black pine (P. nigra) 2 %;
1–2 mm in diameter, before widening into bands. and stone pine (P. cembra) and other pine species
The centre soon turns brown. This is where the < 1 % (Rigling et al. 2021).
fruiting body (0.2–0.8 mm) develops, pushing the In Switzerland, the only effective countermeas-
epidermis of the needle upwards to form a band. ure is to remove an infected tree from the stand.
The spores give the fruiting body a slightly While the wood is not infectious and can be used
olive-green colour. The symptoms are most clearly as firewood, all needles should be burnt on site
visible in early summer. Infected needles turn or disposed of safely (waste incineration). Tool
brown and are shed from the summer onwards. hygiene is important (disinfection with 70 % al-
The pattern of infestation follows a characteristic cohol).
course within the tree: the infestation spreads The symptoms can be confused with those of
from the bottom to the top and from the inside physiological needle blight or infections caused
to the outside. In advanced stages, it is often only by other needle cast fungi such as Dothistroma
the freshly sprouted needles of the youngest gen- spp., Lophodermium seditiosum or Cyclaneusma
1 cm eration that remain green. Especially when the minus. A fresh infection on the needles may be
dead needles are shed, bare branches with tufts mistaken for the bore holes or feeding sites of
of new needles at the branch tips may look a bit insects such as the pine needle weevil (Brachonyx
like trimmed poodles’ tails. pineti).
The fungus overwinters on dead needles, which
remain infectious on the tree or in the litter for up
to six months. It is spread mainly by rainsplash or
WSL Fact sheet 70 (2022) 5Red band needle blight
The non-native red band needle blight (Dothis cases) is most affected, followed by Scots pine and
troma spp.) is one of the most significant diseases black pine (17.5 %, 6 % respectively). In Scots
of pines. There are two species that cause the pines, the disease is most clearly visible on young
disease: Dothistroma septosporum, and Dothis plants. If we look at D. pini separately, we see that
troma pini. They can only be distinguished by black pines are most frequently affected. So far,
means of molecular methods. other species such as the Swiss stone pine (P. cem
Since the 1990s, an increase in both the occur- bra; 1.3 %), other pine species (< 1 %), and spruce
rence and intensity of infestation with the red (Picea abies; 0.4 %) are less frequently infected by
band needle blight has been observed, mainly in Dothistroma spp. (Rigling et al. 2021).
the northern hemisphere. There are two factors The symptoms of red band and brown spot
contributing to this development: it is related to needle blight are very similar. In red band needle
changing climatic conditions such as altered rain- blight, however, instead of the olive-green spots,
fall patterns on the one hand, but on the other there are usually characteristic vermilion or or-
hand also to the planting of already infected or ange-red spots or bands that form. In the centre
susceptible young trees. Whereas D. septosporum of each band, a dark fruiting body develops. The
is found worldwide, D. pini seems to be less wide- fruiting body measures 0.2–0.8 mm in diameter
spread for the time being. After its first discovery and pushes the epidermis of the needle upwards
in Switzerland, red band needle blight was mainly in a similar way to that of brown spot needle
found in urban green areas, usually on single trees blight, forming bands. The red band needle blight
or small groups of trees. From 2013 onwards, it and brown spot needle blight are also similar in
1 cm has also been found locally in forests, where usu- terms of their infestation patterns, overwintering,
ally a dozen to several hundred trees are affected. control measures and possibilities of confusion
Infected are mainly pines, but to a lesser extent with other diseases. The three pathogens that
also genera such as spruce (Picea), fir (Abies), larch cause red band and brown spot needle blight can
(Larix), Douglas fir (Pseudotsuga) or cedar (Cedrus). also occur together, not only on the same tree,
In Switzerland, mountain pine (P. mugo, 69 % of but even on the same needle.
Diplodia pine tip / shoot blight
Pine tip blight (Diplodia sapinea, syn. Sphaeropsis infected. Eventually, the shoots become bent – a
sapinea) is one of the most common diseases symptom that can be exacerbated by insect larvae.
afflicting pine trees, not only in Switzerland but The asexual fruiting bodies are small, black, and
worldwide. Conifers from other genera (e. g. spherical. They occur on the needle, the bark or
Picea, Abies, Cedrus, Larix, Pseudotsuga) can also the cones. On the needle, they are to be found
be affected, but the infestation is usually less especially under the fascicle sheath at the needle’s
severe. base, but in severe cases they appear all over the
In Switzerland, there has been a notable in- needle. If the infection has not arisen after dam-
crease in pine tip blight since 2016. The causes age caused by hail, crown parts close to the
are the hot and dry summers on the one hand, ground are often more severely affected. If the
1 cm
and severe hail storms on the other (Queloz et al. infection spreads to the bark of branches, bark
2018). Black pine remains the most susceptible necroses develop and there may sometimes be
pine species, but mountain and Scots pine are also strong secretion of resin. If D. sapinea penetrates
severely affected in some cases (Queloz et al. into the wood, the wood turns bluish in colour.
2018). Very severe infestation can cause the trees The virulence of the fungus depends on predis-
to die. Among the most obvious symptoms are posing factors such as drought. The link between
the stunted brown needles on the dead brown drought and disease is the subject of many stud-
shoot tips. Usually only the tip (i. e. the youngest ies. Among the diseases that are favoured by
needles) is affected. The fungus is easily recognis- drought, there are several that are accompanied
able as soon as these symptoms appear. by canker and dieback. Pathogens from genera
When a shoot is infected, one of the first signs such as Botryosphaeria, Diplodia, Cytospora and
is the secretion of small droplets of resin from the Biscognauxia (Hypoxylon) are among the best-
buds. Infected buds stop growing. This is why the known pathogens in this context (Desprez-Loustau
needles do not reach their normal size. They re et al. 2006). While drought generally has a neg-
main on the tree for a long time. New buds do ative effect on fungal growth, these genera bene
sprout to replace the dead ones, but they are also fit from the weakening of the host.
6 WSL Fact sheet 70 (2022)D. sapinea can remain in the tissue of the tree at In gardens, attempts can be made to control the
the endophytic life stage for a long time. The fungus by pruning infested shoots back to healthy
growth of other fungi such as Bjerkandera adusta, wood. Tool hygiene through disinfection with
Botrytis cinerea and at least one species of each 70 % alcohol is essential here.
of Armillaria and Rhizoctonia appears to be inhib-
ited by the presence of D. sapinea (de Oliveira et
al. 2019).
Cenangium dieback
The fungus Cenangium ferruginosum occurs pre- bodies develop at the beginning of summer. They
dominantly as a saprobiont on dead branches on are dark brown, 2–3 mm long, and grow out of
all pine species in Switzerland. As a parasite that the stomata of the pine branches. In humid sur-
exploits weakness, it occasionally kills the bark roundings, the fruiting bodies open up to form
and cambium of twigs and branches weakened plate-like structures that are ochre-yellow on the
by environmental factors, other pests, diseases or inside. Under the microscope, Cenangium can be
natural ageing. The fungus has also been found identified by its sexual fruiting bodies and the
in the needles, leading to the assumption that spores they contain. The club-shaped asci contain
these could act as a reservoir storing the patho- eight unicellular, elliptical ascospores (10–13 ×
gen during unfavourable conditions (Sieber et al. 5–7 μm).
1999). Infestation is not fatal for the tree. It is not
At the beginning of spring, the needles of in- necessary to treat this disease in the forest.
dividual twigs or whole branches first turn yel-
lowish-green, then yellow, before turning brown
from the base upwards. They eventually fall off
in summer. If the bark is removed at the base of
dead branches, a sharp line between healthy and
dead tissue becomes visible. The fungal fruiting
1 cm
Scleroderris dieback / Brunchorstia dieback
Scleroderris dieback is one of the more serious spreading from the shoot tip to the needles of
diseases infecting conifers. It causes shoot die- older generations. Over time, bushy growth may
back, but can also lead to extensive damage to occur as the tree attempts to replace dead
the bark in severe cases. The pathogen Grem branches with new shoots. Over the years, de-
meniella abietina (syn. Scleroderris lagerbergii) pending on whether conditions are favourable for
comprises several varieties and subgroups, some the fungus (summers with high levels of precipit
of which favour different pine species. It is wide- ation), or a drier phase slows down its growth,
spread and occurs not only in Central Europe, but the trees may die or recover.
also in East Asia and North America on conifers From the first year of infestation, asexual fruiting
native to these regions. While damage caused by bodies form on the dead twigs and buds. From
this pathogen in Europe before 1960 mainly the second year onwards, sexual fruiting bodies
occurred in Scandinavian Scots pine stands, it in- also appear, in the form of brownish black cuplets
creased in central Europe between 1960 and 1970 measuring 0.5–1 mm in diameter.
(Stephan 1979). Other coniferous genera such as Only silvicultural measures are worth consider-
spruce (Picea), fir (Abies), larch (Larix) and Douglas ing when it comes to minimising damage caused
fir (Pseudotsuga) can also be infected. In winter, by this disease in the forest. Cool-moist stands
resinous lesions form at the base of needles and should for example be thinned at an early stage,
buds, especially on one- and two-year old and afforestation under canopy should be avoided.
1 cm branches. The resinous areas expand and may
encircle the whole branch. The affected areas
wither and die. The needles turn brown from the
base onwards, with the infection subsequently
WSL Fact sheet 70 (2022) 7Snow blight
Snow blight (Gremmenia infestans, syn. Phacid reveals the reddish beige mass of fruiting bodies.
ium infestans) is a typical disease of high altitudes. The spores infect freshly sprouted needles of the
The fungus has adapted to winter conditions in same year and develop internally during the win-
the mountains. It exclusively attacks needles that ter months.
are covered by snow. It is even able to grow in Heavily infested trees can be pruned back to
snow (temperatures below °C). This ability allows health. For this, it is necessary to prune all affected
the fungus to spread from one needle to the next, areas right down to healthy wood. Ensuring a
or from one shoot to another. Small trees and mixture of different tree species can help prevent
seedlings that are completely covered by snow the spread of the fungus.
can die after just one year if infested. Besides
pines, spruces (Picea), firs (Abies) and junipers General source: Kurkela 1996
(Juniperus) are also potential hosts – although they
are infected far less frequently.
With snowmelt in the spring, symptoms become
visible on the trees. Infested needles have a pale
yellow to light brown appearance. Over the course
of the year, they continue to discolour, eventually
becoming a brownish light grey. The tiny fruiting
bodies, up to 1 mm in diameter, push to the sur-
1 cm face from August onwards (often on the under-
side of the needle). The epidermis of the needle
tears open in a star shape as this happens and
Pine blister rust
Pine blister rust (Cronartium pini, syn. C. flac To complete its life cycle, C. flaccidum changes
cidum) mainly attacks Scots and mountain pines hosts, like most rust fungi. Gentians (Gentiana),
in Switzerland, but also other two-needled pine peonies (Paeonia), swallow-wort (Vincetoxicum)
species. The disease is very noticeable with its and some other herbaceous plants are possible
large yellowish-orange blisters. intermediate hosts. Unusually, there is an asexual
The fungus infects young shoots, growing ini- form of the fungus that does not depend on this
tially in their bark for one to two years without change of host and can be transmitted directly
triggering symptoms. Then, in spring, blister-like from pine to pine. This form is more common in
white formations erupt, usually around the branch northern Europe. It has not been conclusively clar-
whorls, turning orange over time. The shoots ified whether these are two distinct species (C. pini
normally die within a couple of years. From the non-host alternating and C. flaccidum host alter-
shoots the fungus penetrates into the trunk, and nating), or whether they are two forms of the
the tree responds by secreting more resin in same species.
affected areas. This leads to a blockage of the
vascular vessels in the cambium (resinification),
and thus to an inhibition or complete interruption
of the water and nutrient transport. Tree parts
above resinified areas die.
1 cm Every year, more bark tissue is killed as the
fungal mycelium continues to grow. The tree
reacts with callus growth that partially overgrows
the affected zone. Over time, affected areas
appear flattened and deformed. Once the tree is
infected, the fungus cannot be eradicated any-
more. On old pines and after years of infestation,
the disease leads to complete crown dieback. On
young pines, death comes as soon as the affected
area encompasses the whole trunk.
8 WSL Fact sheet 70 (2022)Black snow mould
The black snow mould, also known as brown felt les within the felt-like mycelium are still green at
blight (Herpotrichia pinetorum, syn. H. juniperi), first, but die off over time, turning brown in the
like white snow blight, is a conspicuous disease process. The fungus spreads from the needles to
of high altitudes. Several species/varieties exist, the shoots, causing them to die as well. Only after
but morphologically they are hardly distinguish a while do the affected needles and shoots fall
able. One of them, H. coulteri (syn. Neopeckia off.
coulteri), is only found on mountain pine above In the second year, spherical black fruiting bod-
2000 m a. s. l.. Its bicellular spores distinguish it ies form, either on the surfaces of dead needles
from H. pinetorum, the spores of which are (pine and spruce) or within the epidermis (juniper).
quadricellular. The distinction can thus only be Spores formed in the fruiting bodies in late aut
made with the help of microscopic analysis. In the umn infect healthy needles. New needles and
subalpine zone, H. pinetorum attacks mountain shoots can also be infected by the mycelium in
pine, juniper (Juniperus) and spruce (Picea); at winter, similar to the process of infection with
lower altitudes it can also occur on fir (Abies). snow blight.
The most striking symptom is the fine brown- The only effective means of dealing with this
black mycelium that completely envelopes the fungus is to remove and burn the infested mater
needles and shoots. Often the areas close to the ial.
ground are infected, but occasionally whole trees
1 cm
or shrubs. The fungus grows in cavities under the General source: Nierhaus-Wunderwald 1996
snow cover (down to –5 °C). It stops growing
when the snow melts, and its mycelium survives
the dry summer until the next snowfall. The need
Cyclaneusma needle cast
The fungus Cyclaneusma minus (syn. Naemacyclus The spatial distribution of C. minus is rarely even.
minor) triggers the disease Cyclaneusma needle Trees with and without symptoms are usually
cast (also Naemacyclus needle cast). Along with found in close proximity. Infestation can lead to
Lophodermium pinastri, L. seditiosum and Cenan severe needle cast, but is normally more or less
gium ferruginosum, it is one of the most common imperceptible. It is thus not necessary to take any
endophytes affecting pine needles. countermeasures.
Once older needles have turned yellow in sum-
mer and autumn – often with brown-reddish
bands reminiscent of physiological needle blight
– the sexual fruiting bodies form in the litter and
on dead needles on the tree in late winter and
spring. The fruiting bodies are barely 1 mm in
diameter, cream-coloured and, when open, res
emble little windows with light-coloured shutters.
These also serve for identification. Around these
fruiting bodies, the needle often fades to an ochre
brown. The milder and wetter the winter, the more
the fungus spreads. Asexual conidia are produced
throughout the year and continuously infect the
1 cm needles.
WSL Fact sheet 70 (2022) 9Swedish pine needle cast
Swedish needle cast is caused by Lophodermella an isolated, local basis, and does not cause any
sulcigena and is more common in northern Eur major damage. The removal and burning of in-
ope. It attacks various pine species, but especially fested trees has proven effective in controlling the
Scots pine, mountain pine and black pine. disease.
During its one-year life cycle, it infects needles A sister species of this fungus (L. conjuncta) has
in summer. These subsequently die from the tip, also recently been found in Switzerland. This spe-
and turn a yellowish light brown. The base of the cies differs from L. sulcigena in that its fruiting
needle, on the other hand, remains green, and is bodies are far shorter (max. 4 mm in length) and
separated from the dead needle material by a its spores are different (on the right in the picture).
clearly defined brownish-purple band. The need
les and infected short shoots remain on the tree General source: Queloz et al. 2019
until the following year. They continue to fade to
a greyish white. Elliptical black fruiting bodies of
2–20 mm in length develop on the dead needles
(needle on the left in the picture). Affected shoots
and crown areas appear to be pinkish brown from
a distance.
This fungus is a dangerous pathogen, especially
1 cm in Scandinavia. In Switzerland, it only occurs on
Sydowia dieback of pine
Sydowia polyspora is a widespread and extremely black, and spherical, and protrude irregularly from
polyphagous fungus that takes advantage of the colonised plant tissue.
weakened trees and which, as an endophyte, can S. polyspora is very often found in association
also occur in the needles without triggering symp- with pathogenic fungi and also with insect pests.
toms. It probably has the widest range of hosts in In the literature, it is sometimes described as path-
comparison with other fungi associated with con ogenic, although its pathogenicity has not been
ifers. It is also able to colonise all organs of the proven so far. Most likely it is involved in complex
tree. The only exception are the roots, where it diseases, but does not have a strong damaging
rarely occurs. effect on trees on its own.
In slightly symptomatic needles of Scots pine As the pathogenicity of S. polyspora has not as
(yellow to brown spots), the fungus is found par- yet been fully clarified, there are no reliable control
ticularly frequently. In the litter it is often found measures. It is also unclear whether the removal
together with fungi that colonise deadwood. It of diseased parts of the tree right down to healthy
also often occurs on trees that have died from tissue would be beneficial. As a preventive meas-
other causes. Its growth is not limited to the need ure, the strengthening of the general health of
les. It is also able to colonise shoots and even the tree, i. e. through adequate watering and fert
wood. The wood then discolours, turning grey. In ilisation, could prevent damage as the fungus
many conifers, the fungus is found mainly in its profits from its host’s weakness.
asexual form (Sclerophoma pithyophila). The asex-
ual fruiting bodies are very small (200–300 µm),
1 cm
10 WSL Fact sheet 70 (2022)Pine needle rust Literature
Pine needle rust is caused by the rust fungus Coleo Abegg, M.; Brändli, U.-B.; Cioldi, F.; Fischer,
sporium tussilaginis and other very closely related C.; Herold, A.; Meile, R.; Rösler, E.; Speich,
species. To reproduce, it needs two different hosts S.; Traub, B., 2020: Schweizerisches Lan-
(host change) - pines on the one hand, and various desforstinventar LFI. Ergebnistabellen und
herbaceous plants on the other. In the case of Karten der LFI-Erhebungen 1983–2017
(LFI1, LFI2, LFI3, LFI4) im Internet. [Publis-
C. tussilaginis in the narrower sense, the latter are
hed online 10.6.2020] Available from
often coltsfoot (Tussilago). World Wide Web
An infection with a rust fungus is very obvious. Birmensdorf, Eidg. Forschungsanstalt WSL.
The blister-shaped fruiting bodies are 1–3 mm https://doi.org/10.21258/1382821.
wide and protrude from the epidermis of still Behnke-Borowczyk, J., 2018: Biodiversity of
green needles. With their flesh-coloured yellowish fungi community on Scots pine needles
to orange colouring, they stand out against the infected of the autumn needle cast. SYL-
green needles. At a mature stage, the thin skin of WAN 62, 4: 288–294.
the fruiting body tears open, whereupon a yel- Behnke-Borowczyk, J.; Kwasna, H.; Kulawi
lowish-orange spore powder is released. nek, B., 2019: Fungi associated with Cyc
Unlike other needle diseases presented here, laneusma needle cast in Scots pine in the
west of Poland. Forest Pathology 49, 2:
usually only a few needles become infected. Scots
e12487.
pines usually survive an infestation without any Butin, H., 2011: Krankheiten der Wald und
problems. Parkbäume: Diagnose, Biologie, Bekämp-
fung, 4. Auflage. Ulmer, Stuttgart, 318 S.
de Oliveira, C.F.; Moura, PF.; Rech, KS.; Paula
1 cm
de Oliveira, C.D.P.; Hirota, B.C.K.; de Oliv-
eira, M.; da Silva, C.B.; de Souza, A.M.;
Dias, J.D.G.; Miguel, O.G.; Auer, C.G.;
Miguel, M.D., 2019: Antagonistic activity
of Diplodia pinea against phytopathogenic
fungi. Folia Microbio. 64, 3: 415–419.
Desprez-Loustau, M.L.; Marcais, B.; Nagelei-
sen, L.M.; Piou, D.; Vannini, A., 2006: Inter-
Physiological needle blight active effects of drought and pathogens in
forest trees. Ann. For. Sci. 63, 6: 597–612.
Physiological needle blight is a natural process Dubach, V.; Meyer, J.B.; Schneider, S.; Ruffner,
resulting from needle ageing, and one that every B.; Queloz, V., 2018: Nationales Monito-
needle goes through. Accordingly, it is mainly ring von zwei besonders gefährlichen Föh-
older needle generations that are affected. Al- renkrankheiten 2016. Suivi national de
though it is not a disease, the phenomenon is deux maladies du pin particulièrement
listed here for the sake of completeness. It is often dangereuses 2016. Monitoraggio nazio-
reported to the Swiss Forest Protection Group nale di due malattie particolarmente peri-
having been mistaken for a real disease. colose del pino 2016. 34 S.
ETH Professur für Waldbau, Professur für
Pine needles reach different ages, depending on
Forstschutz und Dendrologie, 1995: Mit-
the species. While the needles of the mountain teleuropäische Waldbaumarten. Artbe-
pine are shed after 5–10 years, the needles of the schreibung und Ökologie unter besonde-
Scots pine are shed after 1–8 years (ETH 1995). rer Berücksichtigung der Schweiz. Zürich:
As the needles die, they turn brown. Depending ETH Vorlesungsskript. S. 248.
on the chemical substances deposited in the dying Kurkela, T., 1996: Ascospore production pe-
needles, individual parts of the needles turn to riod of Phacidium infestans, a snow blight
different shades of brown to red. fungus on Pinus sylvestris. Scand. J. For.
Res. 11: 1–4, 60–67.
Lazarevic, J.; Menkis, A., 2020: Fungal Diver-
sity in the Phyllosphere of Pinus heldreichii
H. Christ – An Endemic and High-Altitude
Pine of the Mediterranean Region. Diver-
1 cm sity 12, 5: 172 S.
Nierhaus-Wunderwald, D., 1996: Pilzkrank-
heiten in Hochlagen – Biologie und Befalls-
merkmale. Merkbl. Prax. 27. 8 S.
Nierhaus-Wunderwald, D.; Engesser, R.; Rig-
ling, D., 2012: Hallimasch – Biologie und
forstliche Bedeutung. 2. überarbeitete
Aufl. Merkbl. Prax. 21. 8 S.
WSL Fact sheet 70 (2022) 11Patejuk K.; Cieśniewska, A.B.; Kaczmarek- hoff, E.; Queloz, V., 2021: Überwachung Further information
Pieńczewska, A.; Pusz, W., 2021: Mycobi- von besonders gefährlichen Schadorga-
Used standard references:
ota of peat-bog pine (Pinus × rhaetica) nismen für den Wald – Jahresbericht
Butin 2011, Sinclair und Lyon 2005
needles in the Stołowe Mountains Natio- 2020. Surveillance des organismes nuisi-
nal Park, Poland. Nova Hedwigia 112, bles particulièrement dangereux pour la
waldschutz.wsl.ch
1–2: 253–265. forêt – Rapport annuel 2020. Monitorag-
Queloz, V.; Buser, C.; Dubach, V.; Hölling, gio degli organismi nocivi particolarmente
D.; Meyer, JB.; Schneider, S.; Prospero, S.; pericolosi per il bosco – Rapporto annuale Contact
Cornejo, C.; Rigling, D., 2018: Überwa- 2020. WSL Ber. 108. 99 S.
chung von besonders gefährlichen Schad- Sieber, T.; Rys, J.; Holdenrieder, O., 1999: Swiss Federal Institute WSL
organismen für den Wald – Jahresbericht Mycobiota in symptomless needles of Pi Waldschutz Schweiz
2017. Waldschutz Schweiz / Phytopatho- nus mugo ssp. uncinate. Mycol. Res. 103, Zürcherstr. 111, 8903 Birmensdorf
logie WSL, S. 48. 3: 306–310. waldschutz@wsl.ch
Queloz, V.; Forster, B.; Beenken, L.; Strohe- Sinclair, W.; Lyon H., 2005: Diseases of trees Phone +41 44 739 23 88
ker, S.; Odermatt, O.; Hölling, D.; Meyer, and shrubs. 2nd edition. Cornell University
J.B.; Dubach, V., 2019: Waldschutzüber- Press, New York. 616 p.
Drawings
blick 2018. WSL Ber. 79: 33 S. Stephan, B.R., 1979: Beobachtungen über
Reignoux, S.N.A.; Green, S.; Ennos, R., das Vorkommen und die Variation von Vivanne Dubach
2014: Molecular identification and rela- Scleroderris lagerbergii Gremmen in
tive abundance of cryptic Lophodermium Norddeutschland. Z. Mykol. 45, 1: 45–53.
species in natural populations of Scots Wüest, R.O.; Bergamini, A.; Bollmann, K.; Citation
pine, Pinus sylvestris L. Fungal Bio. 118: Brändli, U.B.; Baltensweiler, A., 2021. Dubach, V.; Queloz, V.; Stroheker, S., 2022:
835–845. Modellierte Verbreitungskarten für die Needle and shoot diseases of pine. WSL Fact
Rigling, D.; Dubach, V., Beenken, L.; Schnei- häufigsten Gehölzarten der Schweiz. Sheet 70.12 p.
der, S.; Hölling, D.; Prospero, S.; Cornejo, Schweiz. Z. Forstwes. 172, 4: 226–233.
C.; Ruffner, B.; Augustinus, B.; Brocker- https://doi.org/10.3188/szf.2021.0226
WSL Fact Sheet ISSN 2624-8069 print / 2624-8077 online
Concept Managing Editor
The Merkblatt für die Praxis summarises key findings from WSL research and Martin Moritzi
provides guidelines for best practice. The series is aimed at forestry and nature Swiss Federal Institute WSL
conservation groups, authorities, schools and interested laypersons. Zürcherstrasse 111
CH-8903 Birmensdorf
French editions are published in the series Notice pour le praticien (ISSN 1012- martin.moritzi@wsl.ch
6554). Italian and English editions appear occasionally in the series Notizie per la www.wsl.ch/merkblatt
pratica (ISSN 1422-2914) and WSL Fact Sheet (ISSN 2624-8069).
The WSL is a research institute of the
Other issues in English (see www.wsl.ch/factsheet) ETH Domain.
Nr. 64: Know, protect and promote habitat trees. R. Bütler et al. 2020. 12 p.
Nr. 61: Cycles and importance of the larch budmoth. B. Wermelinger et al. 2018. 12 p. Layout: Jacqueline Annen, WSL
Druck: Rüegg Media AG
Translation: Tessa Feller
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