Ganoderma diseases of perennial crops in India – an overview

Ganoderma diseases of perennial crops in India–an overviewK.V.Sankaran1,P.D.Bridge2,3&C.Gokulapalan41Kerala Forest Research Institute,Peechi680653,Kerala,India;2Mycology Section,Royal Botanic Gardens, Kew,Richmond,Surrey,TW93AB,UK;3School of Biological and Chemical Sciences,Birkbeck College, Malet St,London WC1E7HX,UK;4Kerala Agricultural University,Vellayani695522,Kerala,IndiaAbstractThe species of Ganoderma recorded from India as causing diseases of perennial crops are listed,and their host range and taxonomy discussed.Four new hosts of G.lucidum are also reported.A decline in pro-ductivity and the death of trees are the main economic impacts due to Ganoderma diseases,and the fungus is identified as a serious pathogen of cash crops,forest plantations and trees in natural forests in the country.Ganoderma diseases have been recorded on144hosts in India,the major pathogens being G.lucidum and G.applanatum.G.lucidum has been recorded on91hosts,and appears to cause the most widespread diseases.Identification has largely been made from morphological and cultural characters,and the names currently in use should therefore be treated with caution.Cultural methods of disease control are largely inefficient in minimising inoculum pressure and in reducing the disease incidence.Chemical methods in combination with soil amendments form short-term solutions for managing the disease and improving productivity.The immediate priorities for developing an efficient management system for Ganoderma diseases in India are:(1)a thorough understanding of the etiology and epidemiology of the diseases on different hosts,(2)clarifying current ambiguity in species names,(3)assessing the inter-relationships be-tween populations of Ganoderma on different hosts and(4)developing tools for early detection of diseases in important crops.Key words:chemical control,cultural control,Ganoderma diseases,host range,India,perennial crops, taxonomyIntroductionThe Indian peninsula has considerable biodiversity due to its unique geographical position,highly di-verse climatic conditions and other related factors. The region experiences extremes of temperature in the north,whereas the climate is more or less equable in most parts of the south.An estimated 27%of the3.287M km2that constitutes India,is natural forests that range from alpine to tropical evergreen.Forests in the northeast and in the Western Ghats in the south are recognized as world biodiversity hot spots[1].May[2]opined that al-though tropical rainforests are known to cover about14%of the world’s land surface,they may house70%of the world species.However,in India,as in many other parts of the world,forests are under great threat,due mainly to human interfer-ence,pests and pathogens.Among the pathogens that pose a threat to natural forests and plantations in the country,the wood rotting fungus Ganoderma is a major factor.This role has become more evi-dent in recent decades as the number of trees af-fected by Ganoderma has risen and the damage this causes to the national economy has increased.Ganoderma,a polyporoid fungus of the order Polyporales,has a worldwide distribution.The genus comprises a large and diverse complex of fungi,many of which are wood rotters and others that are pathogenic on economically important trees and perennial crops.Root and stem rots caused by Ganoderma have long been known toMycopathologia(2005)159:143–152ÓSpringer2005cause extensive losses of many tropical perennial crops such as oil palm(Elaeis guineensis),coconut (Cocos nucifera),betelnut(Areca catechu),tea (Camellia sinensis)and others[3].In India,Ganoderma causes a decline in pro-ductivity and death of several plant species including cash crops such as coconut,betelnut and tea,plantation trees such as Acacia and Albizia, and trees in natural forests including Mesua ferrea, Dalbergia,and Grewia tiliifolia[4–6].Ganoderma also plays a primary role in the decay of wood in natural forests.However,although Ganoderma is of major economic concern to the country,infor-mation on its host range,the extent of damage to host trees,its mode of spread and methods of control are either incomplete or unavailable,with the exception of a few host species.Most of the information available for India is from the northern part of the country and the limited information for the south is largely restricted to a few cash crops such as coconut.This contribution addresses this knowledge gap and provides an overview of the host range of the fungus in India, its taxonomic status,the symptoms on specific hosts and methods of disease management cur-rently adopted in the country.This information is valuable since a prior understanding of the host range of the pathogen,its biology and disease epidemiology are crucial for developing appropri-ate disease management programmes.HistoryThefirst information published on Ganoderma from India dates back to the early1900s[7].Butler [8,9]reported its importance as a pathogen on cash crops such as coconut,betelnut and other planta-tion species including Casuarina,Areca catechu, Dalbergia sissoo and Toona ciliata in the north-eastern states in1906.These reports were followed by the report by Venkatarayan[10]who recorded Ganoderma diseases of coconut,betelnut,Cassia siamea and Pongamia from South India in1936. However,the gravity of the disease problem in forestry crops wasfirst widely publicised by Bag-chee and co-workers[11–14],who reported diseases of forest trees such as Acacia catechu,D.sissoo and Shorea robusta in North India.This initial work was not followed up and since their last publication in1976,most of the publications on Ganoderma diseases have dealt mostly with new disease records and management of the pathogen on coconut,be-telnut,Leucaena and Acacia spp.[6,15–17]. Species of Ganoderma recorded from IndiaA list of the13Ganoderma taxa recorded from India with brief notes on their host range is given below.A complete list of hosts is provided in Table1.Ganoderma applanatum(Pers.)Pat.Recorded on a number of hosts in north,central and south India(Table1).Distributed worldwide with a wide host range.Causes a white soft spongy heart and butt rot[18].G.adspersum(Shulz.)Donk.Recorded on ground from Satara,Maharashtra[19].No further records are available and this may be a misapplied name.Table1.Hosts of Ganoderma spp.recorded from IndiaHost Origin Pathogen Economic use of host Distribution Abies pindrow Royle N GA Timber SAcacia albida Lindl.E GL Firewood RA.aneura F.Muell.ex Benth.E GL Various purposes RA.auriculiformis A.Cunn.ex Benth.E GL Fire wood,pulp WA.catechu(L.f.)Willd.N GA,GL Tannin,dyeing WA.ciliata R.Br.E GL Firewood RA.dealbata Link.E GL Firewood RA.decurrens Willd.E GL Unknown RA.farnesiana(L.)Willd.E GL Essential oil RA.jacquemontii Benth.E GL Unknown RA.leucophloea(Roxb.)Willd.N GL Firewood RA.mangium Willd.E GL Timber,firewood W144145 Table1.(Continued)Host Origin Pathogen Economic use of host Distribution A.mearnsii de Wild.E GA,GL Tannin,firewood SA.melanoxylon R.Br.E GL Timber SA.mollissima Willd.E GL Unknown RA.murrayana F.Muell.ex Benth.E GL Unknown RA.nilotica(L)Del.N GA,GL Various purposes WA.raddiana Savi.E GL Timber RA.senegal(L.)Willd.E GL Gum,adhesives RA.tortilis Heyne E GL Unknown RA.victoriae Benth.E GL Fodder RAcrocarpus fraxinifolius Wight&Arn.N GL Timber RAlbizia chinensis(Osbeck)Merr.N GA,GL Shade tree RA.lebbeck(L.)Benth.N GA,GL Timber WA.odoratissima(L.f.)Benth.N GA Timber SA.procera(Roxb.)Benth.N GA,GL Timber SAnacardium occidentale L.E GL Cashew nut tree SAquilaria agallocha Lam.N GL Various purposes RAreca catechu L.N GL Betelnut tree WArtocarpus heterophyllus Lam.N GA,GL Timber,edible fruits Wkoocha Roxb.ex Buch.-Ham.N GA Timber,edible seeds SAzadirachta indica A.Juss.N GA,GL Medicinal S,RBambusa bambos(L.)Voss N GL Various purposes WBambusa sp.N GL Various purposes SBauhinia retusa Roxb.N GA Ornamental RBombax ceiba L.N GL Matchwood industry WBoswellia serrata Roxb.ex Colebr.N GL Charcoal wood RBuchanania axillaris(Desr.)Ramam.N GC Timber RCaesalpinia pulcherrima(L.)Sw.E GL Ornamental RCajanus cajan(L.)Millsp.N GL Edible seeds RCajanus indicus Spreng.N GL Various purposes RCamellia sinensis(L.)Kuntze E GA,GL Tea WCaryota urens L.E GA Timber,toddy palm RCassiafistula L.N GA,GL Avenue tree S,WC.javanica L.E GA,GL Timber SC.siamea Lam.E GL Firewood SCasuarina equisetifolia L.E GL Various purposes WCedrus deodara(Roxb.ex Lambert)G.Don N GL Timber WCeltis tetrandra Roxb.N GA Timber R Cinnamomum cecidodaphne Meissn.E GA Medicinal RCocos nucifera L.N GA,GL,GC Various purposes W,W,RCoffea arabica L.E GAu Coffee plant SCupania anacardioides A.Rich.E GL Timber RDalbergia latifolia Roxb.N GL Timber SD.sissoo Roxb.ex DC N GA,GL Timber WDelonix regia(Boj.)Rafin.E GL Avenue tree W Dichrostachys cinerea(L.)Wight&Arn.N GL Hedge plant RDiospyros sp.N GL Timber R Dipterocarpus macrocarpus Vesque N GA Timber RDysoxylum malabaricum Bedd.ex Hiern N GL Timber SElaeis guineensis Jacq.E GL Oil palm REucalyptus citriodora Hook.E GL Pulpwood,medicinal REucalyptus spp.E GL Pulpwood WE.tereticornis Smith E GL Pulpwood WFicus benghalensis L.N GL,GC Timber,fibre RFicus religiosa L.N GA,GC Various purposes S,RGrevillea robusta A.Cunn.E GAu,GC Shade tree SGrewia tiliifolia Vahl N GA Timber WGuazuma sp.E GL Timber RG.applanatum var.levisporum Humph.& Leus.Recorded on Quercus incana from north India[20,21].There are no further records available and Steyaert[18]considers this variety as a synonym of G.tornatum(Pers.) Bres.Table1.(Continued)Host Origin Pathogen Economic use ofhostDistributionHevea brasiliensis(A.Juss.)Muell.-Arg.E GL Rubber tree W Hydnocarpus pentandra(Buch.-Ham.)Oken N GL Medicinal RJacaranda mimosifolia D.Don E GL Avenue tree SLannea coromandelica(Houtt.)Merr.N GL Timber SLeucaena leucocephala(Lam.)de Wit.E GA,GL Firewood,pulp R,WLitchi chinensis Sonn.E GL Edible fruits RLitsea monopetala Pers.N GL Unknown RMallotus philippensis(Lam.)Muell.-Arg.N GA Timber,dye RMangifera indica L.N GA,GL Timber,edible fruits WMelia azedarach L.E GL Timber SMelocanna baccifera Kurz N GL Building material RMesua ferrea L.N GL,GC Timber S,R Millingtonia hortensis L.f.E GL Timber,ornamental RMorus alba L.E GA,GL Mulberry SPalaquium ellipticum(Dalz.)Engl.N GP Timber R Paraserianthes falcataria(L.)Nielson E GL Pulpwood SParkia biglandulosa Wight&Arn.E GL Ornamental R Peltophorum pterocarpum(DC.)Baker exHeyneN GL Medicinal,dye RPicea smithiana(Griff.)Henry E GA Timber RPieris ovalifolia D.Don E GA Unknown RPinus roxburghii Sarg.N GA,GL Various purposes WPlatanus orientalis L.E GR Ornamental R Pleiogynium cerasiferum(F.Muell.)Parker E GL Timber SPongamia pinnata(L.)Pierre N GL Firewood SPopulus spp.N/E GL Pulpwood R Pterocarpus marsupium Roxb.N GL Timber SQuercus incana Roxb.N GA,GL,GR Timber RQuercus semicarpifolia Smith N GL,GR Timber S,R Roystonea regia(Kunth)Cook E GL Ornamental RSalix alba L.E GA Timber RSamanea saman(Jacq.)Merr.E GL Avenue tree WSantalum album L.N GA,GL Sandal wood S,RShorea assamica Dyer N GA Timber RS.robusta Gaertner f.N GA,GL Timber W Simmondsia chinensis Schneider E GL Oil yielding RSterculia urens Roxb.N GA Gum yielding RS.villosa Roxb.N GL Timber,fibre SSyzygium cumini(L)Skeels N GC Timber RTamarindus indica L.N GL Timber,edible pulparound seedsRTectona grandis L N GA Timber WTerminalia alata Roth N GL Timber RTerminalia bellirica(Gaertner)Roxb.N GA Timber,tannin WTerminalia crenulata Roth N GL Timber W Theobroma cacao L.E GL Used in confectionary R Thyrsostachys oliveri Gamble N GL Poles RToona ciliata M.Roemer N GA,GL,GC Timber S,S,RGA–Ganoderma applanatum;GAu–G.australe;GC–G.colossum;GL–G.lucidum;GP–G.philippii;GR–G.resinaceum. Derivation:N–native tree;E–exotic.Distribution:W–widespread;S–scattered;R–rare.146G.annulare(Lloyd)Boedijn,Butler and Bisby. Recorded on tree trunks in Darjeeling,West Bengal[22].There are no further records of this species from India or elsewhere.Farr et al.[23] mentioned the occurrence of a G.annularis(Fr.) RL Gilbertson in USA,and whether this is a synonym of G.annualare needs verification.G.australe(Fr.)Pat.Recorded on Grevillea robusta and Coffea arabica from South India (Table1)[24].Also recorded on wood from Assam and Uttar Pradesh[25].Steyaert[26]considers the species to be a synonym of G.tornatum.Farr et al.[23]have reported its occurrence on Acacia and Eucalyptus in USA.G.colossum(Fr.) C.F.Baker.Recorded on eight hosts from India(Table1).Farr et al.[23] have reported its occurrence in subtropical and tropical regions.G.leucophaeum(Mont.)Pat.Recorded on dead wood from Assam[27].No further records are available.Steyaert[18]considers this species to be a synonym of G.applanatum.G.lucidum(Curtis:Fr.)P.Karst.Recorded on 91hosts from all over India(Tables1and2).A cosmopolitan species also recorded from North America,Asia and Europe[23].G.lucidum var.naiae Chona and Munjal.Re-corded on humus in Simla,north India[28].No further records are available and may be a mis-applied name.G.pseudoferreum(Wakef.)Over&Steinm. Recorded on a single host from India[29].Steyaert[28]considers the species to be synonymous withG.philippii(Bres.&P.Henn.)Bres.G.subtornatum Murrill.Recorded on logs from Darjeeling,West Bengal[4].No further records are available and this may be a misidentification.G.wynaadense Steyaert Recorded on stumps of Meusa ferrra from Wynad,Kerala,India[30].No further records are available and this may be a misidentification.G.resinaceum(Boud.)Pat.Recorded on three hosts from north India(Table1)[31].Distribution restricted to Europe according to Browne[32], where it causes diseases on Acer,Pinus and Quercus. Host rangeThe information on host range of Ganoderma in India has been obtained from a large number of sources,although only the main publications are quoted here due to constraints of space[4,11–14, 20,22,32–36].A total of144hosts of Ganoderma are currently known(Tables1and2).This list is by no means exhaustive and some more dubious reports included in obscure publications have not been referred to.No systematic attempt has so far been made to survey the Ganoderma population in natural forests and plantations in India,and it is reasonable to expect that there may be several further species awaiting discovery.Information on the severity of diseases caused by Ganoderma in India is rather scarce.Bakshi et al.[37]reported that Ganoderma caused mor-tality of around55%in9-year-old stands of Acacia catechu in Uttar Pradesh.According to Khara[38] in Ludhiana(Punjab state),13.3%of D.sissoo, 5.5%of Leucaena leucocephala,6%of Delonix re-gia,4%of eucalyptus hybrids and2%of pear trees were severely affected by Ganoderma lucidum.In Tamil Nadu state,the incidence of Ganoderma basal rot was as high as30%in some coconut plantations[5].Table2.Types and numbers of crops affected by Ganoderma and pattern of disease distribution in India Pathogens Hosts Total Disease distributionPlantation and cash crops Forest trees andother speciesWidespread Rare or scatteredGanoderma applanatum1029391425G.australe112–2G.colossum178–8G.lucidum2269912665G.philippii011–1G.resinaceum033–3Total3411014440104147G.lucidum appears to have the widest host range of the pathogens reported;being recorded on 91host plants,the majority of which are forest trees(Table2).It is also the most widely distrib-uted of the species.G.applanatum has the next widest range,having been reported from39host trees,most of which are forest trees.All other species are known from only a few host species. The numbers of exotic and indigenous tree species affected are very similar,indicating that both are equally susceptible to the pathogen.Of the27hosts that are affected by G.lucidum or G.applanatum (on which the diseases are widespread),most are plantation trees and cash crops.Important trees affected by these species are Acacia auriculiformis, A.catechu, A.mangium, A.nilotica,betelnut, coconut,Dalbergia sissoo,Mangifera indica,Pinus roxburghii,Shorea robusta and Tectona grandis.It should be noted that diseases currently recorded as rare or only scattered in occurrence,have the po-tential to become widespread and severe in a short span of time.An example of this is the root rot and wilt of Acacia auriculiformis in Kerala state,which appeared in three isolated localities in1987and has since become a serious problem throughout the state wherever the tree is grown.Among the diseases caused by G.lucidum,basal stem rot(BSR)of coconut wasfirst recorded from Assam in1908[8],and was reported from Tamil Nadu in1952[5].Currently,the disease is pre-valent in most of the north-eastern states,and Karnataka,Maharashtra and Gujarat.Its occur-rence in Kerala state wasfirst noted in Palakkad district in1987[39].The disease is now widespread in Kerala,posing a threat to coconut-based industries and the livelihood of small-scale farm-ers.Bhaskaran suggested that if left unchecked, BSR of coconut could destroy an entire garden in 7–8years[15].BSR of coconut has also been re-corded from Sri Lanka,where the causal organism has been identified as G.boninense Pat.[40].In Malaysia,although sporophores of Ganoderma occur on stumps of coconut palms,it is not known to be pathogenic to coconut,and these sporo-phores possibly act as sources of inoculum for BSR in oil palm[41].BSR of betelnut,which is widespread in India,also occurs in Sri Lanka. Other important trees where Ganoderma diseases have been reported in India and elsewhere are Acacia mangium and Paraserianthes falcataria (Indonesia,Malaysia,Sri Lanka),A.auriculiformis and L.leucocephala(Papua New Guinea), A.mearnsii(Australia,South Africa,Sri Lanka), A.nilotica(Papua New Guinea,South Africa, Indonesia),Albizia chinensis, A.lebbeck and A. odoratissima(Pakistan,Sudan),Casuarina equis-etifolia(Taiwan and UAE),and Dalbergia latifo-lia,D.sissoo and Cassia javanica(Pakistan)[32, 33,35,36,42].BSR of oil palm,which occurs widely in Southeast Asia,is known only from the state of Tripura in India[43].BSR of oil palm has not been detected in extensive surveys in oil palm plantations in Kerala state(results not shown), and it is possible that the disease is more pre-valent in India,but goes unrecorded,as sporo-carps are not produced during the early stages of infection.New host records from IndiaAs part of an extensive survey of Ganoderma dis-eases in Kerala state,Ganoderma has been found on four hosts that had not previously been re-ported as suffering from infection in India.In each case the pathogens were tentatively identified as G.lucidum based on morphological features.The fungus caused a BSR resulting in the death of the trees.Roystonea regia–an exotic ornamental palm growing in the University of Calicut campus, Kerala,India.The disease was recorded in March 2003.Only one tree(8-year-old)was killed and bore sporocarps of G.lucidum,although other trees in the vicinity were at various stages of infection.Peltophorum pterocarpum–an exotic avenue tree planted extensively in Kerala.The disease was recorded in a ca.10-year-old tree growing in the campus of the University of Calicut.The disease was recorded in2003on an isolated tree and no others of this species on the campus appeared in-fected.Parkia biglandulosa–an exotic ornamental tree.A50-year-old tree in the Zoological Museum compound in Thiruvananthapuram was found to be infected about7years ago.The tree was wind thrown in September2002due to heavy infection at the basal region.Sporophores of G.lucidum were collected from the base of the tree during the survey.148Paraserianthes falcataria–this forest planta-tion species is a native of South Asia and is widely grown in Kerala.Ganoderma BSR is widespread on the tree in the State.A40-year-old tree growing in the compound of the University College,Thir-uvananthapuram was found to be infected.An-other nearby infected tree was wind thrown in September2002and sporophores were present on its rotting trunk and base.Apart from these trees,BSR may occur in Va-teria indica L.(a large timber yielding tree indige-nous to India)and Borassus sp.as fruit bodies of G.lucidum were collected on several occasions from the stumps of these trees from Kerala.Disease symptomsThe initial symptom of BSR and root rot was a flaccidity and yellowing of leaves,followed by shedding of leaves and die back of twigs.Gradu-ally most of the branches dried up giving the tree a stag-horn appearance.Oozing of gum from the base of the stem(stem bleeding)was observed in P.falcataria.Severe root rotting can also occur during the advanced stage of the disease.The fungus attacks both sapwood and heartwood, leading to loss of the infected trees due to windfalls or snapping mid-way up the trunk after3–8years, depending on the age and size of the trees. PathogenicityPathogenicity trials are currently being undertaken on seedlings of the host trees.Seedlings were grown in large plastic pots containing a1:1mix-ture of steamed forest soil and sand.Rubber wood blocks(4·2·2cm)were inoculated with myce-lium obtained from the sporophores collected from each host,and the blocks were allowed to become fully colonised.The seedlings were inoc-ulated in June2003by placing the rubber wood blocks in close proximity to the roots of the test plants.The inoculated plants are currently being observed for the development of infection. TaxonomyIn general,the taxonomy of Ganoderma is con-sidered uncertain due to the high phenotypic plasticity of the fruit bodies at macroscopic level and uniformity of microscopic features.Charac-teristics that have been considered in systematic schemes include host specificity,geographical dis-tribution,morphological features of the fruit body including context colour and consistency,the shape of the margin of the pileus,whether the fruit body is stipitate or sessile,and the shape and size of basidiospores[44–46].However,variability in morphological characters has resulted in the investigation of other characteristics to delimit taxa and to understand relationships;and these further characters have included cultural and mating characters,isozyme studies,ribosomal DNA sequences and cladistic methods[47].Al-though molecular techniques can be highly useful in speciation,so far,only a relatively small number of taxa have been considered in this way.Karsten established the genus Ganoderma in 1881with the single species–G.lucidum.Since that time many species names have been proposed and currently there are322names included in Species Fungorum[47],and Moncalvo and Ryv-arden have listed386names for the Ganoder-mateceae as a whole[48].Moncalvo has estimated that there are perhaps60–80true species in Ganoderma[49].Within the current concept of Ganoderma,G.lucidum and G.applanatum are probably the most poorly understood species and two of the most frequently misapplied names[18].The identity of most of the species of Gano-derma recorded from India has been determined from morphological and cultural characteristics alone,and it is therefore not unlikely that many of the names used are incorrect,particularly as G.lucidum and G.applanatum are the names most commonly used in India(Tables1and2).Simi-larly,caution should be taken in the true identity of species known only from single collections. Steyaert considered Bombay to be the southern limit of distribution of G.applanatum[50]and that only G.tornatum occurred south of this,a view that directly conflicts with many Indian identifi-cations.Similarly although the name G.boninense is used for the causal organism of BSR of coconut in Sri Lanka,the same disease is considered to be due to G.lucidum when occurring in India.Lee-lavathy and Ganesh[51]who studied the polypo-rales of Kerala recorded the occurrence of only two species viz.,G.australe and G.lucidum from the State.There are many similar examples of149contradictions in the literature,and these clearly illustrate the confusion over species identities in Ganoderma.ControlThe current methods of control of Ganoderma diseases of perennial crops are aimed at either delaying the progress of infection,or prolonging the productive life of trees.Curative methods are neither practical nor economically feasible in in-fected trees.The three main methods of control are cultural,chemical and biological.The cultural practices involve digging trenches around diseased trees to prevent the spread of the pathogen to neighbouring healthy trees.The size of the tren-ches may vary based on the age and size of the trees.In some cases,the trenches are drenched with chemicals such as formaldehyde to ensure efficacy.The main drawback of this method is that if the trench is not deep enough,or if it is poorly maintained,it will not prevent the roots from spreading.The method of land preparation before replanting has a large bearing on disease incidence, since the residue of infected material left behind can be a good source of inoculum.However,cul-tural practices such as clean clearing,under planting and windrowing have not been widely successful in controlling BSR in oil palm in Malaysia due to some inherent inadequacies of the methods in reducing the inoculum[52].Rethinam[53]suggested a number of practices to reduce BSR in coconut.These included;digging isolation trenches around diseased palms,field sanitation by removal of dead palms and burning the roots,avoiding repeated ploughing,irregular and close planting andflood irrigation,ensuring adequate soil moisture during summer,growing Ganoderma resistant crops such as Ailanthus and banana as inter crops,and avoiding the planting of collateral hosts such as Delonix regia in the vicinity.In India,application of fungicides to control BSR of coconut and other palms is often done in combi-nation with soil amendments such as neem cake (Azadirachta indica)or farmyard manure.Chemicals commonly used include aureofungin,carbendazim, carboxin,copper oxychloride,hexaconazole and tridemorph.These are either root-fed and/or used for soil drenching.According to Bhaskaran[15],root treatment with tridemorph(2ml/100ml)at quar-terly intervals for1year combined with application of5kg neem cake per palm per year controlled BSR of coconut effectively.In another study[5]he found that use of phosphobacteria(200g in10kg of farm yard manure per tree per year)reduced disease severity in coconut compared to treatment with Azospirillum or the VAM fungus,Gigaspora calospora.Naik and Venkatesh[54]proposed the use of2%tridemorph for root feeding and0.1%as soil drench in combination with neem-cake application for managing BSR of coconut in Karnataka.In Kerala,soil drenching with copper oxychloride (0.4%)at the rate of15l/tree is generally practiced to combat BSR of coconut.Biological control of Ganoderma diseases with Trichoderma has been investigated for coconut in India and for oil palm in Malaysia and Indonesia. Bhaskaran[5]reported that application of T.har-zianum either with neem cake(5kg/tree),green leaves(50kg/tree)or farmyard manure(50kg/ tree)+Bordeaux mixture(1%at the rate of40l/ tree)controlled BSR of coconut and resulted in higher nut yields.Application of50g of T.viride coupled with5kg neem cake per palm is reported to give adequate control of BSR of coconut in the coastal districts of Andhra Pradesh[55].Successful management of BSR of oil palm through use of Trichoderma is also reported from Malaysia[56] and Indonesia[57].The efficacy of other antago-nists of Ganoderma viz.,Aspergillus,Penicillium and Gliocladium virens in controlling Ganoderma diseases is yet to be demonstrated.It is essential that strategies for long-term control of Ganoderma be developed urgently to combat the menace.Reduction of inoculum bur-den in replanted areas and use of resistant varieties of the host plants are important points to be considered while developing such strategies. DiscussionThis review indicates that Ganoderma diseases are increasingly becoming significant in India,with the reported number of susceptible hosts increasing in recent years.Control methods are normally at-tempted on cash crops and in plantations,but diseases of forest trees are largely ignored.Unless a strategy to combat the threat is developed ur-gently,the problem could result in large losses of tree crops in India.150。