Current tree disease threats in Scotland

by Dr. Steve Hendry, Forest Research

Transcript

1. Current tree disease threats in Scotland Steve Hendry Forest Research, NRS
2. 25/11/2013 2 Pest / disease Date Phytophthora alni on Alnus spp Dothistroma septosporum on Pinus spp 1993 1997 Phytophthora ramorum on Fagus 2002 Cameraria ohridella 2002 Phytophthora kernoviae 2003 Pseudomonas syringae pv aesculi 2004 Phytophthora pseudosyringae on beech & hornbeam 2006 OPM on Quercus 2006 PTLM on Scots pine 2007 Phytophthora pseudosyringae on Nothofagus and Vaccinium 2009 Phytophthora ramorum on larch 2009 Phytophthora lateralis on Chamaecyparis 2010 Phytophthora austrocedrae on Juniperus 2011 Chalara fraxinea on Fraxinus excelsior 2012 ALB on broadleaves 2012
3. 25/11/2013 3 Chalara dieback of ash Photograph courtesy of Iben Margrete Thomsen, University of Copenhagen
4. 25/11/2013 4 Chalara dieback of ash
5. 25/11/2013 5 • Cause not established until 2006 • Life cycle not clearly elucidated until 2010 and gaps in our knowledge remain • A new disease caused by a fungus (Chalara fraxinea / Hymenoscyphus pseudoalbidus) • Invasive species, origin likely to be eastern Asia • Local spread: wind borne spores • Long distance: plant trade(?) • Widespread in continental Europe • Mainly affects common ash (Fraxinus excelsior) but also other ash species Chalara dieback of ash
6. 25/11/2013 6 Chalara dieback of ash
7. 25/11/2013 7 Chalara dieback of ash
8. 25/11/2013 8 Chalara dieback of ash
9. 25/11/2013 9 Chalara dieback of ash
10. 25/11/2013 10 Chalara dieback of ash
11. 25/11/2013 11 • After their initial formation, lesions do not tend to extend further in subsequent years. • i.e. dieback of trees is not a result of progressive development of existing Chalara cankers in the crowns of trees. • Dieback results from continued episodes of annual infection initiated by ascospores liberated from fruiting bodies of Hymenoscyphus pseudoalbidus produced on the leaf litter. • Disease severity therefore tends to be greatest where accumulation of infected litter can occur. Chalara dieback of ash
12. 25/11/2013 12 Chalara dieback of ash 2007 2008 2009 2010
13. 25/11/2013 13 • Recent research in Scandinavia indicates that Chalara can be found in seeds collected from diseased stands. The process by which this has occurred and the risk of disease transmission via this route is currently under study. • In heavily infected stands, basal stem lesions initiated directly by the pathogen have now been detected in a number of different countries Chalara dieback of ash
14. 25/11/2013 14 • If you find lesions on stems associated with dead side shoots, then you should make sure that the cause is diagnosed!! Chalara dieback of ash
15. 25/11/2013 15 Phytophthora diseases • Phytophthora spp. some of the world’s most destructive plant pathogens • Oomycetes - also known as ‘water moulds’ • Produce free-swimming motile zoospores • Water dispersed • Establish in mild moist climates
16. 25/11/2013 16 Phytophthora diseases
17. 25/11/2013 17 Phytophthora alni
18. 25/11/2013 18 Phytophthora alni • Distribution in Scotland imperfectly known but found chiefly on east coast rivers (including Tweed & Till) to date. • Limited monitoring in late 1990s and early 2000s indicated that rate of development of the disease was not as rapid as in southern England / Wales
19. 25/11/2013 19 Phytophthora lateralis
20. 25/11/2013 20 Phytophthora lateralis
21. 25/11/2013 21 Phytophthora lateralis
22. 25/11/2013 22 Phytophthora lateralis
23. 25/11/2013 23 Phytophthora austrocedrae
24. 25/11/2013 24 Phytophthora austrocedrae
25. 25/11/2013 25 • Phytophthora ramorum emerged in 1990s in Europe and North America • In Europe causing blight and dieback of ornamentals in nurseries • In America causing widespread mortality of oaks – tanoak and coastal Live oak Phytophthora ramorum
26. 25/11/2013 26 First reported in Britain in 2002 • P. ramorum an aerial pathogen, infecting leaves and shoots, as well as bark • Maritime climate of western British Isles ideal for Pr • Pr became widespread on Rhododendron • Rhododendron is a major host – spore production and spread • Commonly found on range of foliar hosts in nurseries and garden centres Phytophthora ramorum
27. 25/11/2013 28 Bleeding lesions on beech Inoculum from rhododendrons Phytophthora ramorum
28. 25/11/2013 29 • In 2009 Pr first reported on Japanese larch in SW England • First finding of infections on a conifer species • Pr now confirmed on JL at ~70 sites in southern England • Spread to Wales, NI and Scotland • Impact on other conifer spp. growing locally (WH, DF, GF) • Removal of larch from FC plantations in West Country Phytophthora ramorum
29. 25/11/2013 30 Infected maturing larch commonly 20-25m tall Young larch (5-8 yr) probably infected from the mature larch Phytophthora ramorum
30. 25/11/2013 31 Pr produces spores on foliage – important source of inoculum allowing aerial spread of the disease – felling of infected trees is therefore essential Phytophthora ramorum
31. 25/11/2013 32 Phytophthora ramorum
32. 25/11/2013 34 • Pr sporulates abundantly on larch needles • Local splash dispersal over a few metres • Sporangia can be dispersed in wind/wind-driven rain up to 4 km • Dispersal over tens of kilometres due to human assisted movement Phytophthora ramorum
33. 25/11/2013 35 • Pr produces chlamydospores on infected tissue • These spores may persist for years • Replanting must take into account this residual inoculum • Use of susceptible hosts to be avoided! Phytophthora ramorum
34. 25/11/2013 36 • Rapid action of felling larch trees appears to have been effective in slowing spread • Devon and Cornwall worst affected – over 3000 Ha of larch felled here • In England very dry periods during spring and autumn in 2011 – peak sporulation times – apparently slowed spread • But wetter than average weather in Scotland during the 2012 growing season probably contributed to an upsurge in cases of the disease in 2013 Phytophthora ramorum
35. 25/11/2013 37 Pinus radiata - NZ, South America, South Africa Pinus ponderosa - North America Pinus nigra var laricio - Europe, NZ (formerly) Dothistroma needle blight
36. 25/11/2013 38 Mycosphaerella pini Dothistroma pini Dothistroma septosporum Unknown Dothistroma needle blight Anamorph (Asexual) Teleomorph (sexual) Disease Dothistroma needle blight
37. 25/11/2013 39 Dothistromin Dothistroma needle blight
38. 25/11/2013 40 Dothistroma needle blight
39. 25/11/2013 41 Processes of infection and dispersal • Water is required for spore release and germination • High humidity within stands increases infection • Infection can occur from 5 – 25oC (optimal ~12 – 20oC) • 10+ hours needle wetness is required • Local dispersal - “splash dispersal” • Mid to long range dispersal - rain, cloud and mist • Long range dispersal - movement of infected plant material Dothistroma needle blight
40. 25/11/2013 42 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 Dothistroma needle blight
41. 25/11/2013 43 Dothistroma septosporum Ethiopia, Mexico and Peru, Bosnia Herzegovina, Macedonia, Montenegro, Norway, Russia, Sweden, UK – Northern Ireland, UK – Wales and the Ukraine Dothistroma pini North central USA (Michigan, Minnesota and Nebraska), France (possibly since 1907), Hungary, SE Russia and the Ukraine Dothistroma needle blight
42. 25/11/2013 44 Scotland CP/LP/SP 2006-2010 Between 06-11 the disease was recorded in: • All 10 FC Districts • Lodgepole pine – ca. 7,500 ha • Scots pine – ca. 3,300 ha we m • Corsican pine – ca. 250 ha • In North Highland and Moray and Aberdeenshire alone, there is significant deterioration of 1.25 million cubic meters s CP LP SP Dothistroma needle blight
43. 25/11/2013 45 Pinus contorta ssp. latifolia Dothistroma needle blight
44. 25/11/2013 46 Pinus sylvestris Dothistroma needle blight
45. 25/11/2013 47 • 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 Dothistroma needle blight
46. 25/11/2013 48 Disease management / control Chemical control - copper fungicides Stand manipulation - Planting density/ thinning / pruning Species change Disease resistance / breeding programmes Dothistroma needle blight