Division of Torest Patbology {Tungal Diseases), Kerala Torest Researcb Institute, Peeehi, Kerala, In A little-leaf disease of Eucalyptus in Kerala, India'' By J. K. SHARMA, C . MOHANAN and E. J. MARIA FLORENCE Abstract A little-teaf disease of Euealyptus tereticornis, E. grandis and E. globulus eharaeterized by stunting of plant.s and considerabte reduetion in size of leaves and internodes, was recorded during survey of nurseries and plantations in Kerala State. The survey indieated that though the little leaf disease was widespread, its incidence was quite low. Transmission of the symptoms by sap and graft techniques was unsuccessful. However, positive fluoreseenee and staining of phloem tissues by Dienes'stain indicat.es that this disease may be eaused by mycoplasnialike organisms (MLO). D u r i n g tbe course of survey of various diseases in nurseries and plantations of eucalypts [Eucalyptus tereticornis Stn., E. grandis (Hills) Maiden, atid E. globulus LabilL] in Kerala, a little leaf disease hitherto unreported, was recorded. The affected plants showed prominent s t u n t i n g and produced much smaller leaves when compared to healthy ones. The new leaves s h e w e d considerable reduction in size and became tbin, pale, scaly witb narrow lamina. Tbe a p i c e s of sucb leaves often sbowed btowmng. The axillary buds were stimulated and p r o d u c e d sboots with abnormally minute leaves. Tbe internodes became abnormally s h o r t e n e d , resulting in a bushy appearance of the shoots (Fig. 1 A, B). The root system of the diseased plants remained apparently unaffected as no abnormality was observed. Affected E. tereticornis trees became weak due to reduction in stem diameter and height growth; ho^vever, in E. grandis apparently no such symptoms were observed, except for the compact b u s h y appearance of shoots, which snapped easily on bending. T o assess the % incidence of little leaf disease a survey was carried out during 1979-1982. F o r t h e purpose five plots each of 400 plants were selected at random in plantation.s and tbe d i s e a s e situation assessed once a year by counting the affected plants. In nurseries also the total number of seedlings showing little leaf symptoms were counted. The total number of seedlings in a standard bed (12 m X 1.2 m) was estimated by tbe seedling density in three 30 cm"^ areas iti the bed atid % tticidence was calculated. T h e survey indicated that though the disease was widespread in the State, the % incidence was below one percent in the plantations (Table I). The disease incidence, recorded in 1- to 5-year-old plantations, was bigber in E. tereticornis tban in E. grandis or E. globulus. Unlike in t h e plantations the incidence of little leaf disease in nurseries was relatively low (Table 2) b e c a u s e of bigh density of the seedling in seedbeds. Furtber, tbe disease was observed more frequently in E. grandis than in E. tereticornis, except in a nursery at Thenoor where the incidence was much higher tban in any of the nurseries of E. tereticornis surveyed. Tbere was also a n indication that different provenances of the same eucalypt species may vary in their level of susceptibility to little leaf disease. E. tereticornis beds raised from seeds collected from a nearby stand grown from pure Australian seeds recorded very low incidence of tbe disease when compared to the E. tereticornis (so-called Eucalyptus hybrid) seeds obtained from Tamilnadu Forest Department. * K F R l Scientific paper No. 14. U.S. Copyright Clearance Center Code Statement: 0 3 0 0 - 1 2 3 7 / 8 3 / 1 3 0 7 / 0 3 8 5 / $ 02.50/0 Eur. J. For. Path. 13 (1983) 385-388 © 1983 Verlag Paul Parey, Hamburg und Berlin ISSN 0300-1237/lnterCode: EJl'PA 9 / . K. Sbarma, C. Mobanan and E. J. Maria Florence 386 fig. /. Typical symptoms of little-leaf disease. A. Eucalyptus tereticornis (twoyear-old), B. E. grandis (Coppice shoots) The little leaf disease is suspected to be seed-borne as it is seen appearing even in very young seedlings. Tbe reason for observing the disease more frequently in E. grandis than in E. tereticornis in the nursery as compared to the plantation may reflect late expression of symptoms in the latter speeies, which may be related to the seed source and the climatic conditions. This was later confirmed in the nurseries situated at Chandanathode (Wyanad Division) and Peechi (Trichur Division) by makitig observations at regular intervals from the day of emergence till the saplings were 10 months old. Tbe typical symptoms of abnormal leaves appeared in E. grandis as early as one month following emergence whereas in Table I Incidence of little-leaf disease of E. tereticornis, E. grandis and E. globulus recorded in various parts of Kerala Host species Year of planting Locality l'ore.st Range Forest Division % incidence E. teretieornis 1979 1976 1979 1976 1979 1976 1979 1978 1980 Kakkavayal Ncllikkara Cheenkannipally Varavoor Kottappara Anakulam Mullachal Noolpuzha Mavinhalla Thalayar Pappathishola Silent Valley Tamarassery Taniarassery Tamarassery Wadakanchery Kodanad Peringamala Sultan's Battery Sultan's Battery Devicoltim - Kozhikode Nilambur Nilambur Trichur Kothamangalam Punalur (KFDC)' Trivandrum(KFL:)C) Kozhikode Kozhikode Munnar Munnar Munnar (K.FDC) 0.4 0.25 0.125 0.05 0.17 0.08 0.42 0.05 0.0 0.05 0.58 0.35 E. grandis 2 E. globulus 1978 1979 ' Kerala Forest Development Corporation, ' Not known. 387 A little-leaf disease of Eucalyptus in Kerala, India Eig. 2. S y tiiptotiis of litde-leaf disease produced in four-iiionth-old seedlings of £. teretieornis (A, B) and f. grandis (C) E. tereticornis it took normally 3-5 months for expression of the symptoms. In both the eucalypts prior to the appearance of the disease all the leaf pairs produced on the seedlings were apparently healthy and of normal size (Fig. 2). Occurrenee of isolated eucalypt tree(s) in plantations anci variation in disease incidence in different provenance of the same species of eucalypt at Thenoor rule out the possibility of association of little leaf symptoms with any nutritional deficiency in the soil. Since no fungal or bacterial isolations could be made from the plant parts (leaves and roots) of the affected Table 2 Incidence of little-leaf disease of Eucalyptus recorded in various nurseries situated in different locations during 1980-1982 Host species Yc'.ir mii-.scry Total no. of seed be.ls(l2xl.2m) raised grandis tereticornis grandis grandis tereticornis grandis tereticornis grandis tereticornis tereticornis 1980 1980 1981 1981 1981 1982 1982 1982 1982 1982 30 52 40 100' 100' 45 45 7' 120 8 E. tereticornis (commcTiily called Eucalyptus liyhrid) 1982 42 E. E. E. E. E. E. E. E. E. E. LOCTIUV Forest Ranj;e Potta Wadakanchery Wadnkanchcry Pott;l Siiltan'.s Battery Potigali Chaiid.inathode Katiiioth ClKiiidaii;ithodc Kannoth Chaiidanathode Kantioth Ch.iiidaiiatliodo Kannoth Peechi Uppukuzhi Kothamangalam Tliciioor Pciinganiala (Palode) Tlieiioor Peringamala (Palode) I'ore.sl Division Trichur RFDC' Trichur KFDC' Kozhikode Mnnantodv Man an tody Manantody Manantody KI'Rl C.mipu.s Kotlianiaiigalani Trivandrum (KFDC) Trivandrum (KFDC) ' bed size 3 in X 1 in; E. teretieornis and E. grandis wer• .sown in half of the bed separately. ^ K e r a l a Fore.st Developinciit Corponition. % Incidenee O.OII 0.00 0.015 0.032 0.005 0.074 0.003 0.096 0.008 0.002 0.2.54 388 ]. K. Sbarma, C. Mobanan and E. J. Maria florence trees, infection due to a viral or mycoplasmalike organisms (MLO) was suspected. Graft and sap transmission studies for both the little leaf dtseases from E. tereticornis and E. grandis were conducted employing six months old plants of E. tereticornis, which even after six months did not yield any positive results. Earlier SASTRI et al. (1971) have reported a graft transmissible little leaf disease in four or five years old trees of E. citriodora Hook, which was stated to be caused by a virus. As most of the little leaf diseases reported so far are caused by MLO, graft transmtsston studies on plants of different ages of both the species were repeated following standard procedures but even after one year of grafting no symptoms have appeared. Since tbe symptoms of little leaf disease are expressed earlier in E. grandis than in E. tereticornis it is suggested to attempt transmission of the causal organism on £. grandis. Although the positive fluorescence and staining in phloem tissues with Dienes' stain (DEELEY et al. 1979) have been observed, which is an indication of possible association of MLO with tlie little leaf disease, a transmission electron tnicroscopic study of the diseased tissue IS warranted to confirm the presence of MLO tn the phloem tissue. Acknowledgements Authors are thankful to Mr. K. YESODHARAN, Field Assistant for technical assistance and Mr. SUBHASH KuRtAKOSH for photography. Resume Une maladie des petites feuilles de I'Eucalyptus a Kerala (hide) Une maladie des pctitcs feuilles A' Eucalyptus tereticornis, E. grandis ct E. globulus cnracteriscc par le rabougrissemcnt des plnntcs, unc reduction considerable dans la taille des feuilles ct des etitrenoeuds, a etc rcpercc lors dc surveillance de pepinicTcs et dc plaiuattotis dans TLtat de Kerala. I.'cnqticte a montre que, bien que la maladie des potitcs feutlles fCit largement rc'panduc, son importance etait tres faihle. La transmis.sion des symptomes par In scvc ou par des techniques dc greffage a cchouc". Toutefois, des effets positifs cn fluorescence ct la coloration des tissus du libcr p.ir In coloration dc Dicnc indiquent que cette maladie pourrait c'tre provoquee par des organismes voisins des mycoplnsmcs (MLO). Zusammenfassung Eine ,,little-leaj-Erkrankurig" an Eukalyptus in Kerala, hnlien Im Zugc cincr Inveiuur der Bnumschulen und Kulturen wutde nn Eucalyptus tereticornis, E. grandis und E. globulus cine litilc-lcnf-Krkrankung bcohnclitct, die sich durch Wuchsstauchungcn sowie durch crhcblichc Vcrkurzungen der Blatter und Internodien hcnicrkhnr machtc. Trotz woitcr Vorbroitung diesor Krnnkhcit ist der von ihr vcruisnchtc Schaden nur gering. Die Obertragung durch Saft- und Pfropftcchnikcn mifSlang. Positive F.rgchnisso von Fluorcszcnz und Fnrbovorsuchon dos Pliloemgewehcs (Dienos-Tcchnik) ln.ssen iodoch erwarten, dnl5 die Krnnkheit von mycoplasmaahnlichen Organismon (MLO) nusgolost wird. Literature SASTRY, K . S. M . ; THAKUR, R . N . ; GUPTA, J. H . ; PANDOIRA, V. R., 1971 ; Throe virus disonsos of Eucalyptus citriodora. Indian Phytopath. 24, 123-126. DEELEY, ] . ; STEVENS, W . A.; Fox, R. T. V., 1979: Uso of Dienos'stnin to detect plnnt diso.-isc induced by mycoplasmalike organisms. Phytopathology 69, 1169-1171. Authors' address: Dr. J. K. SHARIVIA, Mr. C. MOHANAN and Mrs. E. ] . MARIA FLORI;NCE, Division of Forest Pathology (Fungal Diseases), Kerala Forest Research histitute, Pceclii 680653, Kerala, Indin Receipt of Ms. 13. 1. I9H3