Short introduction to major damage agents and their management

Olli-Pekka Tikkanen

School of Forest Sciences/UEF

Biotic Forest Damages in Finland

Climate change and recent increase of temperature sum• New species have emerged which can be harmful• Epidemics of some ”old species” have increased since 2000

Cold climate protects Finnish forests largely from biotic damages• Low temperature sum, short growing season• Only periodic mass epidemics of few insect species• Few fungal diseases causing chronic epidemics• No serious problems caused by alien invasive species (so far)

density after hunting seasonin 2017 (ind./1000 ha)

2018, 87 000 animals

Size of moose populationin winter

The big issue: Moose (Alces alces)

Moose migrations and winter aggregations=> damages to young stands in winter (birch, pine)

Proportion of young stands damged by moose

NFI 10

S-FinlandN-FinlandWhole country

Pro

vin

ces

appr. 18 %

Moose damages in private forests in 2018

Hunting licenses bought by hunters => Compensations paid to forest owners€ => €

Damage Control by hunting

”Moose economy areas”• Sustainable pop size

2-3 indiv./1000 ha• Number of available

hunting licenses

Annosus Root Rot, several species world wide

Heterobasidion annosum sensu stricto (P-strain) H. irregulare (P-strain, N-America)

H. parviporum (S-strain )H. occidentale (S-strain, N-America)

H. abietinum (F-strain) not in Finland

H. araucariae not in Finland

FUNGI

Symptoms of Heterobasidion annosum

-canopy gaps made by dead & dying pines

-resin extraction in the butt of Pine tree

Hinders transportation of water to the tree crown => wilting of tree.

10

Butt rot is difficult to detect without cutting

the tree or taking core sample

A swollen butt of stem is NOT a clear

and certain symptom

Resin flow in but indicates the

presence of fungus and rot

Heterobasidion species produce ”white

rot”

Fruiting bodies are an unambiguous

indicator (on lower surface of roots

and stems of downed trees)

Identification of H. parviporum infection (on Picea abies)

H. parviporum

Distribution of H. parviporum and H. annosum

H. annosum

http://www.metla.fi/metinfo/metsienterveys/lahontorjunta/kuusi-juurikaapa.htm

Annosus root & butt rot

Costs to silviculture eg.

• Declined quality of timber

• Declined growth, especially in pine stands

• Increased mortality

• Wind damages

• Costs of sanitary fellings & biological control

• In spruce stands, wide spread presence of H.

parviporum may forece adoption of unoptimal,

shorter stand rotation time => decline of timber

revenue

Biological control of H. parviporum

Phelbia gigantea suspension (RotStop ®)

Wood decaying fungus which is not harmful to living trees

Outcompetes H. parviporum

Untreated stump Urea treatment RotStop

ManagementStump treatments for preventing new spore infectionsAvoidance of thinning in infected stands

In southern Finland, stumps must be treated by biological or chemical Heterobasidioncontrol suspension, if trees are cut when the temperature is above 0 °C and there is no snow cover. (Forest protection act 264/2016)

Stem & shoot diseases

Scleroderris cankerGremmeniella abietina (Lagerb.) Morelet, syn: Ascocalyx abietina (Lagerb.) Schläpfer

Scots pine blister rust, Peridermium stem rust, cronartium rust

Cronartium flaccidum (Alb. et Schw.) Wint., Peridermium pini (Pers.) Lev

Pine twisting rust Melampsora pinitorqua (Braun) Rostr.

Symptoms of Scleroderris canker

• Pole stage pines• Dead and browned shoot tips (with dead buds) all over

the tree crown or only in lower part of the crown• Cankers in branches• In cankers, xylem of tree (and in dead shoots) is

yellowish green (not blue). Bark and epidermis brown (not black).

• Apothecia (fruiting bodies) present in dead branches and shoots (not always)

Scleroderris canker, Gremmeniella abietina

SexualReproduction

cycle

AsexualReproduction

cycle

Öllölä, August 2017

Importance of G. abietina

• The most common and important pathogen of Pinussylvestris in southern Finland

• NFI: found in 10 % of pine stands, declined quality of stand in 2.6 % in Southern Finland

• may kill even larger pine trees

• decline in growth increment, malformations of trunk

18

Major epidemy in 1980’s

Scleroderris canker 8. & 9. NFI

8th NFI 1986-1994 9th NFI 1996-2003

30-40 %16-18 %

Factors increasing the probability of epidemic

• Increase in the occurrence after cool and rainy growing seasons

• Wrong origin of seedlings; too southern proveniences has been used in silviculture!

• Local climate or stand micro climate is moist• Macro topography: High altitude; water shed areas

• Micro Topography has high importance: depressions and ravines

• Stand density

• High productivity stands, especially on stands growing on mineral soil

• Fine grained soils on high altitude (naturally spruce stands)

• MANAGEMENT: sanitary thinnings• Improves micro climate of stand and decreases the amount of

infection sources

Managment of infected stands

Quoted from Sikström et al. 2017

• “for sanitary thinning, Scots pine trees with a foliage loss of 80 % and higher should be cut, to provide a high probability for survival of Scots pine trees after a G. abietina attack, as well as a safety margin against the risk of T. piniperda stem attacks”

• “If the forest stand has a very low stocking level after a sanitary thinning it may be better to carry out a final felling of the stand“

Swedish recommendations

Ips typographus, Coleoptera, Scolytidae

• Length 4.2 -5.5 mm• The economically most important

insect pest of spruce • Feeds under thick bark• Adult, dark brown, hairy• Four teeth in on both sides of

margin of elytral declivity

Monitoring Ips typographus

• Populations of I. typographus can be monitored by using pheromone traps

• In Finland monitoring started 2012 using the same method as in Sweden and Norway

• The population level estimates obtained in pheromone monitoring can be used in risk assessment of I. typographusdamages =>

• information to forest owners

• effective targeting of field inspections and salvage loggings in high risk areas

• supervision of obedience of legal regulations about the storage of timber and removal of large amounts of wind throws

Pheromone trapping &monitoring

Three traps in a triangle (side 2 m) in fresh clear cut about 20 m from forest edge.

So called “Norwegian” type tube trap or “Borregaard” trap

Ipsowit® pheromone bait inside

Neuvonen ym. 2014

Results of pheromone monitoring 2012

No. adult I. typo /Group of 3 traps

Outbreak risk threshold

Neuvonen ym. 2014

Results of pheromone monitoring 2013

No. adult I. typo /Group of 3 traps

Extremely high risk area

High risk area

Why population densities of Ips typographus are rising above outbreak level in Finland, in 2010’s?

Previous epidemic in early 2000’s after severe wind damages

The largest outbreak epidemic so far started in 2011

Severe summer storms in 2010Winter storms in 2011

Recent major storm events in Finland

Plenty of suitable breeding material

Factor 1

Factor 2

Steady rise in effective temperature sum after 2000

More surviving offspring and increase of population growth potential

• Management of SBB problem

• Monitoring by forest authorities ?• Forestry Legislation: Fresh spruce

timber and wind throws must be transported from forest before the emergence of new beetle generation• A zone: 15 July• B zone: 24 July• C zone: 15 July

• No explicit statistics about the damages

Defoliating insects

Pine (Pinus sylvestris)Hymenoptera (Symphyta)

Tenthredinidae: Neodiprion sertifer, Diprion piniPamphiliidae: Agantholyda posticalis, Agantholyda spp.

LepidopteraNoctuidae: Panolis flammeaGeometridae: Bupalus piniarius

Spruce (Picea abies)Hymenoptera (Symphyta)

Tenthredinidae: Pristiphora abietina

Birches (Betula spp.)Lepidoptera

Geometridae: Epirrita autumanta, Operophtera brumata

Other deciduous trees with aesthetic landscape valueYponomeutidae: Yponomeuta evonymellusGeometridae: Operophtera brumata

Sawflies (Hymenoptera, Tenthredinidae)

Neodiprion sertifer, Fox-coloured sawfly

• Frequent epidemic outbreaks throughout the distribution area of the species (Paleartic)

• Introduced accidentally to Nearctis in 1900’s• Primary pine defoliator in NW Europe - so far?; a huge mass

epidemy of Diprion pini in early 2000’s

Juutinen & Varama (1986)

Total damage area in maximum year 1981= 68 000 ha

• Nuclear polyhedrosis virus (NPV) an important pathogen that often infects the larvae in outbreak densities => natural collapse of population, usually in the 2nd year of the outbreak

End of epidemics

• NPV is species specific pathogen, does not harm other insects

• Commercial biocides were developed in 80’s eg. Monisärmiövirus ™

• Use of NPV-based biocides is not approved in EU

• License is too expensive for occasional need

• In high population densities, some individuals do not emerge but stay as pupa 1-3 years and emerge later as adult.

• In severe outbreak years, in some cases, 50 % of pupae can be in diapause and overwinter

• Adaptation to potential depletion of foliage and escape from pathogens, such as NPV, and specialist parasitoids.

• Egg parasitism – another important density dependent source of mortality

• Pupal predation controls populations in productive, mesic forest stands => outbreaks more often on xeric and sub xeric forest stands

Pine sawfly, Diprion pini

• Common in pine forests in whole Europe and Asia• Several different “races” and “ecotypes” in different

parts of it’s distribution area• Gregarious larvae -> group feeding, in August-October • Overwintering as pupa in detritus • Adults emerge in June-July in several pulses

Sawflies (Hymenoptera, Tenthredinidae)

Epidemic mass outbreaks

• Large epidemic mass outbreaks typical

• Within sawflies, the most important forestry pest in Central Europe

• In Finland, the largest epidemic was in early 2000’s, covering total area of 500 000 ha, area of serious damage 200 000 ha

• 7 larger epidemics during past 20-30 years

Economical damages of pine sawflies in forestry

• Feeding of needles reduces photosynthetic surface of trees => less resources to allocate in growth and other traits => decrease in tree vigor.

• Lowered diameter increment => declined timber production

• Already one season defoliation leads to reduced diameter increment

• Economical impact of growth loss is more difficult to estimate than in the case of bark beetles. In most cases the tree will survive (bark beetles kill trees and monetary loss is easy to calculate).

• Secondary pests may create additional problems and even kill weakened trees: such as shoot borers (Tomicus spp.)

• In boreal NW Europe, moderate defoliation by N. sertifer causes 33 % reduction of increment growth.

• Severe defoliation leads to 40% reduction in increment growth.

• N. sertifer does not feed on current year needles.

• Mortality of trees around 4%

• Diprion pini: moderate defoliation causes even 85% reduction in increment; feeds also on current year needles

• Serious defoliation - 100% loss in increment growth

• Tree mortality 30-70%

Economical damages of pine sawflies in forestry

(Lack of) Management of saw fly damages

Long intervals between population peaksSmall forest holdings in Southern Finland

No monitoringLate recognition of damages

Use of control methods (NPV or Bt) needs lots of byrocracy

Saw fly populations colapse naturally before any action is managed to taken (slow reaction)

Cyclic outbreaks of Epirrita autumanta and Operophtera spp.Damage and kill tree line mountain birch forests in Lapland

Operophtera brumata outbreak Skiippagurra, Norway, June 2016

Warming climate, insect herbivores and overgrazing

• During the last decade, a massive outbreak has swept across northern Fennoscandia,

• as much as 1/3 of the birch forest has been affected belt by severe defoliation in one or more years

• In recent decades, the outbreak ranges of both Epirritaautumnata and the more oceanic winter moth Operophterabrumata have expanded into more continental and colder inland areas, where cold winters previously protected birches

• Heavy over grazing by reindeer hinders regeneration of mountain birch

• Studied in Kevo biological station