of Basal Stem Rot Disease of Coconut Caused by Ganoderma lucidum

Management R. 10Bhaskaran of Basal Stem Rot Disease of Coconut Management of Basal Stem Rot Disease of Coconut Caused by Ganoderma lucidum R. Bhaskaran 10 Coconut Research Station, Tamil Nadu Agricultural University, Veppankulam, Tamil Nadu, India Introduction Basal stem rot (BSR) disease of coconut, hitherto called Thanjavur wilt, was first noticed in 1952 in Thanjavur district of Tamil Nadu (Vijayan and Natarajan, 1972). This disease is also prevalent in Andhra Pradesh, Karnataka, Maharashtra and Gujarat States, and is referred to as Ganoderma root rot, Ganoderma wilt, Ganoderma disease, anabe or bole rot (Nambiar and Rethinam, 1986). Wilson et al. (1987) reported the occurrence of a BSR disease in coconut in Kerala. In some of the more severelyaffected coconut gardens, the incidence of the disease is as high as 30% (Bhaskaran and Ramanathan, 1984) and if the disease is left unchecked, it maydestroythe entire coconut garden within a period of 7 8 years, if the conditions are favourable for the spread of the disease. Exudation of reddish-brown, viscous fluid from the basal portions of the stem, which graduallyextends upwards, severe root rotting, decayand discolouration of internal tissues of the stem, drooping of leaves and death of the palm are the characteristic symptoms of the disease (Bhaskaran et al., 1989). Occasionally, some infected palms do not show bleeding symptoms, but the other symptoms will be present. Ganoderma lucidum (Leyss) Karst and Ganoderma applanatum (Pers.) Pat. were isolated from the roots of diseased palm. The above-ground parts of the palm are free from the pathogen. On inoculation, G. lucidum alone was able to infect and produce symptoms of the disease (Bhaskaran et al., 1991). CAB International 2000. Ganoderma Diseases of Perennial Crops (eds J. Flood, P.D. Bridge and M. Holderness) 121

122 R. Bhaskaran Management of the Disease Effect of Trichoderma harzianum application with organic manures Afield experiment was initiated during May 1992, to study the effect of T. harzianum, the fungus antagonistic to G. lucidum, in the control of BSR. The antagonist was multiplied in rice bran sawdust medium and applied to the basins of the diseased tree with different organic manures. The treatments were given once a year. The results showed that T. harzianum applied with green leaves, neem cake (NC) or farmyard manure + Bordeaux mixture (FYM + BM) were more effective for the management of the disease than other treatments and control (Table 10.1). All the treatments recorded significantly higher nut yields than the control. FYM, FYM + BM and neem cake treatments were superior to other treatments. In addition to assessing disease, microbial populations in the organic manures applied were estimated at bi-monthly intervals for 1 year using a serial dilution plate technique. In general, fungal populations increased markedly up to the fourth month after treatment in all treatments containing organic manure and decreased thereafter except in treatment with green leaves, where the population continued to increase up to the eighth month. In all the organic manure treatments, fungal populations were much higher than in control soil; FYM and NC recording very high population levels (20 and 18 10 4 cfu g 1 of soil in FYM and NC treatments, respectively, 1 year after treatment) (Fig. 10.1). The bacterial population was high in FYM treatment, followed by tank silt (TS) and the population dynamics followed almost the same trend as that of fungi, i.e. increase up to the fourth month and thereafter a reduction (Fig. 10.2). Actinomycete populations increased in the FYM and TS treatments Table 10.1. Effect of Trichoderma harzianum with different organic manures on basal stem rot intensity and nut yield. Treatment T. harzianum in 5 kg neem cake T. harzianum with 50 kg farmyard manure (FYM) T. harzianum with 200 kg tank silt T. harzianum with 50 kg coir dust T. harzianum with 50 kg composted coir dust T. harzianum with 10 kg poultry manure T. harzianum with 50 kg green leaves Bordeaux mixture (BM) 1%, 40 litres T. harzianum with FYM + BM Control CD (P = 0.05) Disease Index 26.0 48.4 59.5 100.0 57.2 72.8 23.0 38.6 28.7 92.1 4.3 Nut yield per palm 1993/94 97 101 83 88 90 84 88 92 96 44 5

Management of Basal Stem Rot Disease of Coconut 123 Fig. 10.1. Effect of organic amendments on populations of fungi in soil. FYM, farmyard manure; NC, neem cake; GL, green leaves; TS, tank silt; CD, coir dust; BM, Bordeaux mixture; C, control. (Fig. 10.3). These populations increased up to the eighth month and then decreased (Fig. 10.3). Trichoderma populations were high in all the organic manure treatments when compared to the control (Table 10.2). The population increased up to the fourth month and then decreased drastically, although the populations always remained much higher than control soil even in the twelfth month after treatment. NC and FYM sustained the highest population levels. Effect of biofertilizers Afield experiment was initiated to test the efficacy of biofertilizers in the management of BSR. Azospirillum, phosphobacteria and the vesicular arbuscular mycorrhizal (VAM) fungus Gigaspora calospora were tested. Peatbased inoculum of Azospirillum and phosphobacteria (200 g) in 10 kg of FYM per tree year 1 was used. Soil inoculum of VAM fungus (500 g) was used for each tree.

124 R. Bhaskaran Fig. 10.2. Effect of organic amendments on the soil bacterial population. FYM, farmyard manure; NC, neem cake; GL, green leaves; TS, tank silt; CD, coir dust; BM, Bordeaux mixture; C, control. Disease intensity, recorded up to the end of 1993, indicated that phosphobacterial treatment was effective in reducing the disease severity when compared to the other biofertilizers tested (Table 10.3). Nut yield was higher in all the biofertilizer treatments as compared to control. Although phosphobacteria recorded a mean nut yield of 100, which is less than that of G. calospora and Azospirillum, the yield increased in 1993 when compared to the yield in 1991, while with the other two biofertilizer treatments there was no yield increase when compared to that in 1991 (Table 10.3).

Management of Basal Stem Rot Disease of Coconut 125 Fig. 10.3. Effect of organic amendments on actinomycete populations. FYM, farmyard manure; NC, neem cake; GL, green leaves; TS, tank silt; CD, coir dust; BM, Bordeaux mixture; C, control. Table 10.2. Effect of organic manures on Trichoderma population. Populations months after inoculation Treatments 0* 4* 8 ++ 12 ++ Neem cake Farmyard manure (FYM) Poultry manure Tank silt Composted coir dust Green leaves FYM + Bordeaux mixture 52 44 40 38 37 28 46 Control 0 0 0 0 Population 10 5 (*) and 10 3 (++) cfu g 1. 64 70 54 48 52 12 60 48 37 35 30 36 40 40 45 40 32 34 30 28 38

126 R. Bhaskaran Table 10.3. Effect of biofertilizers on disease intensity and nut yield of basal stem rot-affected coconut (experiment initiated in September, 1990; mean of five replications). Disease index Nut yield % Increase over Treatments 1991 1992 1993 1991 1992 1993 Mean control Azospirillum 200 g per 10 kg Phosphobacteria 200 g per 10 kg Gigaspora calospora Control CD (P = 0.05) 21.6 1.7 20.2 24.9 2.8 53.3 4.9 45.7 55.3 4.2 64.3 34.8 50.6 79.0 3.7 113 87 108 78 7 112 110 118 77 15 92 102 108 76 5 106 100 111 77 3 37.7 29.9 44.2 Efficacy of fungicides In the field experiment on the efficacy of fungicides in the management of BSR, fungicides were given as root feeding at quarterly intervals for 1 year and 5 kg of NC was applied every year. The results (Table 10.4) indicate that aureofungin-sol and tridemorph are very effective during the first 3 years, but in the subsequent years the disease intensity gradually increased. This indicates that the trees are not permanently cured of the disease and there is only suppression of symptoms. Conclusion Basal stem rot disease is a major disease limiting coconut production in India. Treatment of the diseased palms with fungicides does not offer a permanent cure to the affected tree. Biological control with T. harzianum and phosphobacteria offers some scope for containing the disease but organic amendments are essential to encourage antagonistic microflora, and treatments which included organic amendments had least disease and better yields of coconuts than those without amendments.

Management of Basal Stem Rot Disease of Coconut 127 Table 10.4. Efficacy of fungicides in the management of basal stem rot disease of coconut. Disease Index Nut yield per palm Treatments 1988 1989 1990 1991 1992 1993 1988/89 1989/90 1990/91 1991/92 Mean Neem cake 5 kg (NC) + carbendazim 2gin 100 ml of water as root feeding NC + carboxin 2 g in 100 ml as root feeding NC + aureofungin-sol 2 g with 1 g of copper sulphate in 100 ml as root feeding (NC + AF) NC + tridemorph 2 ml in 100 ml as root feeding NC + aureofungin-sol + 40 litres of 1% Bordeaux mixture (NC + AF + BM) Control CD (P = 0.5) 26.5 38.2 6.3 11.1 7.0 43.6 4.6 95.5 96.0 8.6 18.2 11.6 97.5 15.9 25.6 19.6 23.6 16.6 99.0 45.8 31.3 35.9 98.5 19.5 96.0 54.3 42.5 50.7 99.0 19.6 95.3 99.5 64.3 52.4 58.6 98.5 19.8 53 71 92 61 114 53 7 48 64 117 106 127 57 10 55 59 121 90 104 31 10 10 2 58 42 62 4 12 42 49 97 75 102 36

128 R. Bhaskaran References Bhaskaran, R. and Ramanathan, T. (1984) Occurrence and spread of Thanjavur wilt disease of coconut. Indian Coconut Journal 15(6), 1 3. Bhaskaran, R., Rethinam, P. and Nambiar, K.K.N. (1989) Thanjavur wilt of coconut. Journal of Plantation Crops 17, 69 79. Bhaskaran, R., Ramadoss, N. and Suriachandraselvan, M. (1991) Pathogenicity of Ganoderma spp. isolated from Thanjavur wilt affected coconut (Cocos nucifera L.). Madras Agricultural Journal 78, 137 138. Bhaskaran, R. and Ramanathan, T. (1984) Occurrence and spread of Thanjavur wilt disease of coconut. Indian Coconut Journal 15, 1 3. Nambiar, K.K.N. and Rethinam, P. (1986) Thanjavur wilt/ganoderma disease of coconut. Pamphlet No. 30, Central Plantation Crops Research Institute, Kasaragod. Vijayan, K.M. and Natarajan, S. (1972) Some observations on the coconut wilt disease of Tamil Nadu. Coconut Bulletin 2(12), 2 4. Wilson, K.I., Rajan, K.M., Nair, M.C. and Balakrishnan, S. (1987) Ganoderma disease of coconut in Kerala. In: International Symposium on Ganoderma Wilt Diseases on Palms and Other Perennial Crops. Tamil Nadu Agricultural University, Coimbatore (abstr.), pp. 4 5.