An introduction to Needle Blight

Dr Anna Brown, Forest Research

Dr Kath Tubby, Martin Mullett and Richard Baden and nomenclature A simplified history of the anamorph taxonomy 1911 - - Cytosporina septospora 1931 - Europe - Cytosporina septospora reclassified as Septoriella septospora 1917 - NA - Actinothyrium marginatum 1941 - NA - Dothistroma pini Hulbary 1954 - Europe- Dothistroma pini Hulbury. 1967 - Cytosporina septospora = Dothistroma pini so reclassified as Dothistroma septospora 2004 - molecular analysis showed two distinct , Dothistroma septosporum and Dothistroma pini

A simplified history of the teleomorph taxonomy 1957 - Europe - pini 1966 œ Canada - Scirrhia pini 1966 - Scirrhia pini re-classified as Eruptio pini 2001 œ Reclassified back to Mycosphaerella pini Current status

Current EU legislation Scirrhia pini

Teleomorph Mycosphaerella pini Unknown

Anamorph Dothistroma septosporum Dothistroma pini

Disease Dothistroma Needle Blight Symptom and infection process

Dothistromin Symptom and infection process Disease progression Required conditions

• Natural spore dispersal

• Water is essential

• Spores released in water and become caught droplets

• Local dispersal is from runoff and splash

• Highest infection within 100 yards, dramatic drop off by 200 yards but still occurring at 300 yards

• Longer dispersal probably via wind driven rain and mists and cloud

• Spores trapped in mist 10 feet above canopy Required conditions

• Spore germination

• Humidity >75% and availability of free water

• Temperature 5-30oC, optimum 17-22oC

• Temperature can be raised and lowered and spores will germinate when returned within the limits

• Light œ no impact

• Incubation period between 4 and 38 weeks - dependent on climatic conditions (e.g. warmer and higher light intensities generally faster), and host type Persistence

• Persistence on fallen needles

• In NZ on P. radiata

• Suspended - at least four but less than six months • Litter layer - at least two but less than four months

• In UK on P. nigra ssp. laricio

• Suspended - at least seven months • Litter layer - at least five months Dothistromin

• Toxin produced by both Dothistroma spp.

• Responsible for the red colouration produced in the necrotic areas

• Structurally similar to versicolorin B (an aflotoxin precursor produced by some Aspergillus spp.)

• Induces plant defences and shown to provide a competitive advantage against other fungi (in vitro)

• Levels produced vary by >500 fold, although limited sample tested

• Weak mutagen and clastogen and thus potentially carcinogenic Susceptible hosts = 86 Pinus spp.

Highly susceptible-- P. attenuata, P. x attenuradiata, P. brutia, P. canariensis, P. cembroides, P. contorta var. latifolia, P. engelmannii, P. halepensis, P. jeffreyi, P. muricata, P. nigra subsp.laricio, P. nigra subsp. nigra, P. pinea, P. ponderosa, P. radiata, P. sabineana, P. sylvestris, P. thunbergii

Moderately susceptible-- P. bungeana, P. canariensis, P. caribaea, P. coulteri, P. cubensis, P. densiflora, P. echinata, P. echinata x taeda, P. elliottii, P. flexilis, P. jeffreyi, P. kesiya, P. lambertiana, P. massoniana, P. monticola, P. mugo subsp. Mugo, P. muricata, P. occidentalis, P. palustris, P. pinaster, P. pungens, P. radiata var. binata, P. resinosa, P. roxburghii, P. strobiformis, P. strobus, P. taeda, P. thunbergii

Slightly susceptible- P. aristata, P. ayacahuite, P. contorta, P. coulteri, P. devoniana, P. elliottii, P. elliottii var. densa, P. hartwegii, P. heldreichii, P. koraiensis, P. merkusii, P. montezumae, P. monticola, P. nigra subsp. nigra, P. oocarpa, P. patula, P. pseudostrobus, P. rigida, P. sabineana, P. serotina, P. sibirica, P. strobus, P. strobus L. var. chiapensis, P. sylvestris, P. tabuliformis, P. taeda, P. torreyana, P. wallichiana

Susceptibility unknown - P. albicaulis, P. arizonica var. cooperi, P. banksiana, P. cembra, P. clausa, P. contorta x banksiana, P. contorta var. contorta, P. kesiya var. kesiya, P. maximinoi, P. mugo subsp. rotundata, P. mugo subsp. uncinata, P. peuce, P. sylvestris . var mongolica, P.tecunumanii Other susceptible

And seven non- Pinus species…...

• Larix decidua • Picea abies • Picea omorika • Picea pungens • Picea sitchensis • Picea shrenkiana • Pseudotsuga menziesii

However, all are thought to be of low susceptibility ……………………….. World distribution

(Presumed) Dothistroma septosporum

Ethiopia Mexico and Peru Bosnia Herzegovina, Macedonia, Montenegro, Norway, Russia, Sweden, UK œ Northern Ireland, UK œ Wales and the Ukraine European distribution 2009

Presumed Dothistroma septosporum

2008 o

2009 1911 2007 2008

2011 2008 2005

1955 1990 1995 2007 2008 2000 2004 1983 2000 1961 1997 1966 1990 1975 1977 1968 1989 1986 2005 1958 1986 1977 1975 1980-1981 Before 2008 1986 Known D. pini distribution

• North central USA (Michigan, Minnesota and Nebraska)

• France (possible since 1907), Hungary, SE Russia and the Ukraine

• The two Dothistroma species are only distinguishable using molecular methods. W hy now?

1.Climatic conditions • Increase in frequency of days where temperature => 18- 20˘C with 3d rain + found in UK and Canada

2. Species composition • large areas of single species and in some countries, reliance on a low number of species

3. Plant Trade • e.g. regular outbreaks in nurseries since 2005 in GB

4. Genetic diversity of the pathogen • Both mating types and high genetic diversity may =>aggressiveness + >hosts Impact œ yield

• Loss in yield due to needle necrosis and premature defoliation leading to loss of subsequent photosynthetic ability.

• Young trees ca. <10 years

• all needles equally efficient thus a liner relationship between infection and growth

• Greatest reduction seen in height increment

• Older trees

• If infection is low, little impact as older needles (which are infected first) are less efficient

• If infection >25% greatest reduction in diameter increment

• If infection 75% or > diameter growth practically ceases Impact - yield

0.03 Pre-infection

0.025 Post-infection

0.02

0.015

0.01 AnnualAnnual VolumeVolume IncrementIncrement

0.005

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 Tree Age Impact œ mortality

• Mortality observed where infection levels high for successive years -

• 60% in three years in P. radiata stands, Canada

• 68% in two years in P. radiata stands, California, USA

• Over 90% in P. ponderosa stands, Illinois, USA

• 6% per annum in P. nigra subsp. laricio, and 20% per annum in P. contorta var. latifolia, UK

• In NZ annual timber losses (mainly from loss in yield) is between ca. 20 and 25 million NZ$ despite control measures Management - silviculture Thinning and pruning reduces infection levels

• increases air circulation and decreases humidity

• decrease needle drying time and thus infection

• removes infected material

• and, for thinning, increases the distance between trees and thus the effectiveness of rain splashed spores

Pruning - in NZ, reduced infection levels for 2 to 5 years

Thinning - in Australia infection lower if crowns > than 2.5m apart and increase if closer than 1m Management - silviculture 70 NT ST HT 60

50

% ImpactImpactFactorFactor % % 40

st Mortality per annum : nd 1 - 1% in the thinned 2 thin - 3% in the un-thinned thin 30 2004 2005 2006 2007 2008 2009 2010 Year Management - silviculture

8000

7000 Standard

6000 Heavy

5000

4000

3000

2000

1000

0 Mean radial increment (microns) (microns) increment increment radial radial Mean Mean 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Management - chemical

• Many fungicides have been found to be effective

• Copper fungicides e.g. copper sulphate or copper oxychloride are most widely used

• In NZ

• applied routinely via aerial applications (up to 200 tonnes/annum

• may require 2 applications per year but generally once every 3 years and new techniques may increase this window to every 5/6 years

• suppress the disease œdo not —cure“ the tree

• Questions over ability to spray in Europe (legislation) and required frequency (and thus financial viability) as different silviculture/climate/hosts Management œ Resistance/ breeding

• Some disease resistance reported within species • Varieties of P. nigra from Serbia and Bosnia Herzegovina and P. ponderosa from the Rocky Mountains

• P. radiata breeding programme in New Zealand • Families and hybrids of radiata that incorporate Dothistroma resistance predicted to have a 12% reduction in crown infection • Dothistroma resistance is a moderately heritable and is a quantative trait and therefore can collect seed from resistant clones.

• Breeding programme likely to be less successful if D. septosporum is able to reproduce sexually and generate geneticdiversity(Hirst et al., 1999)

• Lifecycle ofatree vs. a fungiandtherefore evolutionaryrate Management œ forests

W here is it and on what species?

How severe is it? i.e. 50% mortality, 1 ys needle retention

W hat is the site type?i.e. what management is appropriate? What other factors may be influencing the crop?

W hat else is on the site? i.e. can secondary species be adopted?

W hat areas are we talking about? 10 ha infected in a 1000ha forest or 13,000 ha infected in a 15,000 ha forest?

W hat are the markets (for dead/dying timber) and how does this influence management priorities? Management œ nurseries

Areas to consider include œ

• Nursery location œ presence of DNB and/or pine in surrounding area

• Stocking options œ seed vrs plants, movement of stock, seed hygine, species and origins, proportion of pine

• Nursery practice œ awareness raising, biosecurity, fungicides, exposure period, stock position and weed control Hosts and impact Pinus contorta ssp. latifolia Hosts and impact Pinus contorta ssp. latifolia Impact Pinus sylvestris Hosts and impact Pinus sylvestris