04270nas a2200145 4500008004100000245012300041210006900164300000700233490000700240520377500247100001504022700001504037700001704052856005504069 2010 eng d00aDieback and mortality of plantation Japanese larch (Larix kaempferi) associated with infection by Phytophthora ramorum0 aDieback and mortality of plantation Japanese larch Larix kaempfe a190 v223 a

The invasive pathogen Phytophthora ramorum is the cause of ’sudden oak death’, a dieback and mortality of more than one million live-oak and tanoak trees along 1500 km of near-coastal native forest in California and Oregon since 1995 (Rizzo et al., 2002; Frankel, 2008). P. ramorum has also spread across Europe , mainly within the ornamental nursery trade. From 2003 onwards it was found infecting rhododendron and woodland trees outside nurseries in Britain (Brasier et al., 2004) and has recently spread to native Vaccinium swards (P. Beales, personal communication). Until now, tree infections in Britain have been comparatively few (<100), mostly foliage or stems of Fagaceae (Fagus, Nothofagus, Quercus and Castanea) in the vicinity of infected Rhododendron in south west England (Webber, 2008). In August 2009 extensive dieback and mortality was observed in mature (25-30 m tall) and juvenile plantation Japanese larch, Larix kaempferi,at multiple sites in south west England (Figs. 1, 2). Symptoms included black or purple discoloured needles (Fig. 3), aborted bud flush, wilting and senescence of dwarf shoots and needle loss. Affected trees often had copious resin bleeding on the trunk, branches and side shoots plus dieback of branches and sometimes of the entire crown. Phloem lesions were often present under resinous outer bark. These usually had deep pink to maroon-red margins, older lesion areas being rusty-brown to cinnamon brown.

When symptom-bearing needles were surface-sterilised in 70% ethanol for 30 seconds or small pieces of older phloem lesion were plated onto Phytophthora selective medium (Brasier et al., 2005), P. ramorum was obtained from 25-40% of the samples. Identity was confirmed by sequencing of ITS rDNA regions (GenBank Accession No. HQ010359). P. ramorum was not obtained from the pink-maroon lesion margins. Pathogenicity of a P. ramorum isolate from L. kaempferi was tested by dipping 15 cm long L. kaempferi shoots into a zoospore suspension and damp chamber incubating for 12h light/12h dark cycle at 18°C. On half the shoots all needles were wounded by tip cutting. After seven days each needle was categorised as blackened, browned/brown bands, chlorotic or green, surface sterilised and plated onto selective medium. Both unwounded and wounded blackened needles yielded P. ramorum at high frequency (Table 1). When needles were mounted in lactic acid cotton blue and viewed 24 h later, sporangia and occasionally chlamydospores were observed on the surfaces with an exceptional 2685 sporangia counted on one unwounded needle (Fig. 4).

P. ramorum has so far been isolated from L. kaempferi at 68 currently known plantations where symptoms are present in southwest England . In May 2010 larch plantations with similar symptoms were discovered in south Wales and P. ramorum has again been isolated at multiple sites. Overall an estimated 2400 ha or c. 0.6 million mature larch have been affected to date. A large area of juvenile larch is also affected. This is the first widespread and lethal damage caused by P. ramorum to a conifer and the first to a commercial plantation tree. Adjacent to some affected larch sites in southwest England , secondary infection of Fagus sylvatica, Nothofagus obliqua, Castanea sativa, Betula pendula, Rhododendron ponticum, Tsuga heterophylla and Pseudotsuga menziesii is also occurring, apparently as result of the high levels of P. ramorum inoculum produced from larch foliage.  

1 aWebber, JF1 aMullett, M1 aBrasier, C M uhttp://dx.doi.org/10.5197/j.2044-0588.2010.022.01902312nas a2200193 4500008004100000022001400041245007700055210006900132260002900201300001200230520172200242100001501964700001901979700001501998700001802013700001702031700001502048856005502063 2011 eng d a1439-032900aIsolation of Phytophthora lateralis from Chamaecyparis foliage in Taiwan0 aIsolation of Phytophthora lateralis from Chamaecyparis foliage i bBlackwell Publishing Ltd ano–no3 a

Summary Following the discovery in 2008 of Phytophthora lateralis in forest soil under old-growth yellow cedar (Chamaecyparis obtusa var. formosana) in north-east Taiwan, further sampling was undertaken in the same region. Soil, root and symptomatic foliage samples were collected from five separate sites where C. obtusa was the dominant species in cloud forests at ca. 1800–2500 m. Soil and fine root samples were baited with cedar needles; both direct isolation and cedar needle baiting were used on foliage samples. Phytophthora lateralis was obtained from soil at three of the sites, but only from three of the 27 soil samples overall. Only one of 25 root samples yielded the pathogen, and this was associated with infested soil. Three foliage samples with symptoms visible as dark brown to black frond tips also yielded P. lateralis; these came from two different sites. This is the first record of P. lateralis infecting the foliage of C. obtusa. Moreover, when some of the symptomatic Chamaecyparis foliage segments were incubated, sporangia of P. lateralis formed on the necrotic tissues, sometimes in the axils of needle segments. The study provides evidence that P. lateralis has both a soil/root infecting phase and an aerial or foliar infecting phase in Taiwan, which is consistent with its unusual combination of water-dispersed (non-papillate) and aerially dispersed (caducous) sporangia. It also demonstrates the importance of investigating the biology, aetiology and ecological behaviour of Phytophthoras in their native, endemic environments.

1 aWebber, JF1 aVettraino, A M1 aChang, T T1 aBellgard, S E1 aBrasier, C M1 aVannini, A uhttp://dx.doi.org/10.1111/j.1439-0329.2011.00729.x