Phytophthora Austrocedrae - Forestry Journal

Feature: Phytophthora austrocedraeAustrocedrus chilensisthe candidate coniferthat never wasGovernment scientists are trawling the treesof the world to find suitable candidatesto cover the anticipated effects of climatechange now predicted by most of the‘movers and shakers’ in forestry. Newlyidentified tree species could be used fortimber or biomass in the commercialforestry industry and for aesthetic, scenicand pollution-tolerant qualities in urbanforestry within the arboriculture and amenitysectors. Being free from economicallycrippling diseases is an important prerequisitefor use.Temperate South America includingsouthern Argentina, Chile and the PeruvianAndes is an under-exploited source ofnovel tree species. The region is not wellblessed with endemic conifers but thosepresent such as Austrocedrus chilensisappear to offer good opportunities throughbeing highly adaptable trees that wouldcertainly thrive in significant areas of the UKenvironment. The only ‘fly in the ointment’is that major primary diseases appearto be arriving in the UK before the treesthemselves with P. austrocedrae and A.chilensis as the classic case.Austrocedrus chilensis (ciprés de lacordillera or Chilean cedar) is an endemictree in the Cupressaceae found in southernArgentina and Chile and is the mostwidely distributed amongst the relativelyfew conifers found inhabiting southernArgentina. That said, the tree is highlyversatile and adaptable being found across140,000 hectares in a wide variety ofecological niches and different soil types.It grows between latitudes 36°30’S and43°35’S on the eastern slopes of the Andesand between latitudes 32°39’S and 44°S onthe western slopes.In Argentina it grows in a 60- to 80km-widestrip along the Andean foothills and acrossa broad moisture gradient from 1700 mm/year in the west to 50 mm/year in the east.In the west A. chilensis can be found eitherin mixed stands with Northofagus spp.With the arrival of Phytophthora austrocedrae thefuture of common juniper, one of only three nativeBritish conifers and increasingly rare, must be inserious jeopardy. (Picture courtesy Forestry Commission).(southern beeches) or in pure Austrocedrusstands on drier sites. In the north, it canbe found mixed together with Araucariaaraucana (Monkey Puzzle tree). It alsogrows in open xeric forests or in isolatedclumps at the limit of the Andean forestand the Patagonian steppe, acting as abarrier against desert advance. A. chilensisis valued not only because of its ecologicalfunction but also because of the quality ofits wood and its scenic importance.Sadly A. chilensis is the primary host ofPhytophthora austrocedrae already in thewider UK environment with eradicationnow virtually impossible. This means theUK cannot now benefit from the attributesthat this highly versatile conifer could haveoffered.Reference: Greslebin, A.G. and Hansen, E.M. (2010)Pathogenicity of Phytophthora austrocedrae onAustrocedrus chilensis and its relation with mal delciprés in Patagonia. Plant Pathology 59:604-612.Chilean cedarthe primary hostof Phytophthoraaustrocedrae in itsnative Patagonia(South America) growsalongside a not verycommon but still wellknownarb conifer inthe UK – the MonkeyPuzzle tree shown here.(Picture courtesy ForestryCommission).P. austrocedraechanges the gameplay for juniperScotland had enough Phytophthoraproblems without Phytophthoraaustrocedrae turning up last year. Thisfirst UK finding of P. austrocedrae wasbad enough but the latest revelationsconcerning the pathogen killing wildcommon juniper in Upper Teesdaleis potentially terminal for commonjuniper in Scotland and for the futureof this British native conifer in the UKas a whole. This is because Scotland iscurrently home to around 80% of theremaining wild common juniper in theUK with only one third of Scottish sitescalculated to have strong and securejuniper populations.Restoring juniper in woodlands and atwoodland edges is critical to its chancesof survival says Forestry CommissionScotland and Plantlife, the wild plantconservation charity. New grants arenow available from the Scotland RuralDevelopment Programme (SDRP) to helplandowners conserve and regeneratesmall populations of juniper andimprove long-term survival in sites acrossScotland.Plantlife’s Conservation Manager,Deborah Long, said: “Juniper is badlyaffected by browsing and grazinganimals, land clearance and land usechange and uncontrolled ‘muirburn’[burning moorland to maintain thehabitat for red grouse]. Old bushesaren’t producing much viable seed.It’s clear that juniper is not going tostage a comeback without our help andthankfully landowners can help solvethese problems. With concerted actionwe can help revive the species and makeit a common and widespread feature inour landscapes.”All this was said before P. austrocedraewas found killing juniper in UpperTeesdale. With juniper characteristicallygrowing in colonies on restricted sitesthe omens for this native species are notgood if P. austrocedrae starts to spread.These Scottish colonies and sites canbe as strong as you like but massedranks of juniper bushes will not stop anaggressive Phytophthora pathogen like P.austrocedrae – on the contrary they willfacilitate its spread.The focus should be on restoring oldjuniper sites especially down the driereastern half of the UK and across southeast England where moisture-lovingPhytophthora pathogens are least likelyto thrive. Sites along the Surrey Hills(North Downs) such as Box Hill areclassic examples where common juniperwas once a common feature on chalkyescarpments but is now increasingly rare.34