Indian Phytopath. 63 (1) : 63-65 (2010) Management strategies against frog eye leaf spot pathogen (Cercospora nicotianae) in India SHAMARAO JAHAGIRDAR and A.R. HUNDEKAR Department of Plant Pathology, University of Agricultural Sciences, Dharwad 580 005 ABSTRACT: Frog eye leaf spot caused by Cercospora nicotianae has become a major threat in recent years accounting to economic loss of 5-50% in India. The field level investigations were taken up with new agro-molecules from 2003 to 2006 at the research farm and large scale demonstrations in farmer’s fields during 2007. The pooled results revealed that spraying of propiconazole @ 0.1% or carbendazim @ 0.05% recorded very low Percent Disease Index (PDI) (23.3 to 23.7). The maximum PDI of 42.9 was recorded in untreated check. Higher yields were obtained in carbendazim or propiconazole sprayed plots with significant superiority over check. Growth parameters like plant height, leaf length and leaf width were also influenced by new molecules accounting to better cured leaf yield and superiority in quality parameters. Net income (Rs.22, 250 per ha) was obtained by carbendazim spray treatment followed by Rs.20,690 per ha with propiconazole. Two sprays with hexaconazole (0.1%) or propiconazole (0.1%) or Carbendazim (0.05%) at 65th and 80th days after transplanting helped in strategic management of frog eye leaf spot with production of excellent quality bidi tobacco in India. Key words: Frog eye leaf spot, Cercospora nicotianae, Nicotiana tabacum The frog eye leaf spot disease caused by Cercospora nicotianae Ell. and Eve. is a major problem in both nursery as well as in the main field in bidi tobacco growing environments. Humid and warm weather during AugustSeptember is highly congenial for development of the disease. Losses due to this disease have been estimated to the tune of 23 per cent in bidi tobacco (Nicotiana tabacum) under normal monsoon conditions of Gujarat (Anonymous, 1978). The status on importance and scope of management of bidi tobacco diseases in India has been reviewed by Kulkarni et al . (2005). Nicotine, reducing sugars and chloride contents are very important to assess the quality parameters of bidi tobacco. Frog eye disease infected plants were less in nicotine content (46.7%) and reducing sugars (24.3%) compared to healthy leaves in nursery (Patel et al., 2001). However, there was no information on development of field level management strategies for frog eye leaf spot in the subcontinent on bidi tobacco using triazoles. Keeping these points under consideration the present investigations were taken up to assess the bioefficacy, cured leaf yield, economics and quality parameters analysis under field conditions in Indian bidi tobacco. The results of investigations are presented in this paper. MATERIALS AND METHODS Field investigations were carried out at the All India Network Research Project on Tobacco at Agricultural Research station (ARS), Nipani (University of Agricultural Sciences, Dharwad) from 2003 to 2006 in a randomised block design with three replications. Each treatment was designed with plot size of 4.0 x 7.5 m. In total six different new molecules belonging to triazole and other groups were evaluated for bioefficacy, yield, economics and quality on highly *Corresponding author: shamaraoj@gmail.com susceptible and popular cultivar A-119 viz., T1= Hexaconazole 5% EC @ 0.1%, T2= Propiconazole 25% EC @ 0.1%, T3= Chlorothalonil @ 0.2%, T4= Carbendazim12% + Mancozeb-63% @ 0.2%,T5= Thiophanate methyl 70% WP@ 0.2%, T6= Carbendazim 50%WP @ 0.05%, T7= Control were imposed with first spray at disease appearance followed by another spray at 15 days interval. All the recommended agronomic practices were followed. The observations on Percent Disease Index (PDI), Cured leaf yield, growth parameters were recorded at periodical inter vals. The data was statistically analysed as per procedures of Sukhatme and Amble (1985).The economics was worked out for each treatment based on yield and cost of production. Leaf samples from treated and untreated plots were collected randomly at appropriate stage for estimation of nicotine, reducing sugars and chlorides which were analyzed at Quality Parameter Assessment Laboratory, Central Tobacco Research Institute, Rajahmundry. RESULTS ANS DISCUSSION The results of investigation are presented in Table 1 to 3. Management of frog eye leaf spot with new molecules hexaconazole @0.1%( 25.5 PDI) or propiconazole @ 0.1% (23.7 PDI) exhibited significant superiority over untreated check (42.9 PDI) and per se performance with positive check carbendazim(23.3 PDI) in both individual years and pooled basis (Table 1). The cured leaf yield also exhibited numerical superiority of new molecules over positive check (carbendazim) and other test fungicides in individual years (Table 2).However, there was significant superiority of hexaconazole@0.1% (1121kg/ha),propiconazole @ 0.1%(1146 kg/ha), and carbendazim@0.05%(1158 kg/ha) over chlorothalonil (1085 kg/ha) on pooled basis (Table 2). Minimum cured leaf yield was recorded in untreated check (1007 kg/ha).Though, there was no significant superiority 64 Table 1. Effect of fungicidal management of frog eye leaf spot of bidi tobacco on the disease index and plant growth parameters Treatment Percent Disease Index 2003-04 2004-05 2005-06 Growth parameters 2006-07 Pooled Pooled over years (2003 to 2006) Plant height (cm) Leaf length (cm) Leaf width (cm) 1 Hexaconazole 5% E.C. @ 0.1% 28.1 (32.1)* 18.9 (25.8) 26.7 (31.1) 28.2 (32.1) 25.5 (30.2) 80.0 46.8 18.0 2 Propiconazole 25% E.C. @ 0.1% 28.4 (32.2) 19.2 (25.9) 26.2 (30.8) 27.1 (31.4) 23.7 (29.1) 79.9 45.8 18.7 3 Chlorothalonil 75%WP @ 0.2% 31.6 (34.2) 28.2 (32.2) 31.9 (34.4) 32.9 (35.0) 30.2 (33.2) 79.8 49.4 19.3 4 Carbendazim-12% + Mancozeb-63% @ 0.2% 26.8 (31.2) 23.4 (28.9) 27.2 (31.4) 33.4 (35.3) 27.6 (31.7) 76.9 46.5 18.4 5 Thiophanate methyl 70% WP @ 0.2% 29.4 (32.8) 29.7 (33.0) 28.7 (32.4) 37.3 (37.6) 31.1 (33.9) 77.9 47.4 19.3 6 Carbendazim 50%WP @ 0.05% 24.9 (29.9) 19.4 (26.1) 24.1 (29.4) 24.5 (29.7) 23.3 (28.7) 78.5 47.6 19.6 7 Control 44.0 (41.5) 45.3 (42.3) 54.3 (47.5) 55.9 (48.4) 42.9 (46.6) 76.1 45.6 20.02 S.Em± 0.91 1.29 1.26 1.62 1.18 1.65 0.89 0.56 C.D. 5% 2.77 3.84 3.75 4.82 3.51 NS NS NS C.V. % 5.10 9.83 7.49 7.76 7.07 4.21 3.81 5.93 Indian Phytopathology Sl.No. *Arc Sine Values Table 2. Effect of fungicidal management of frog eye leaf spot of bidi tobacco on the cured leaf yield and chemical constituents of leaves Sl. Treatment No. Cured Leaf Yield (kg/ha) 2003-04 2004-05 2005-06 Chemical constituents 2006-07 Pooled Nicotine (%) Reducing sugars (%) Chlorides (%) 1 Hexaconazole 5% E.C. @ 0.1% 939 1333 921 1292 1121 3.56 7.19 0.41 2 Propiconazole 25% E.C. @ 0.1% 900 1304 1000 1380 1146 3.46 7.17 0.66 0.42 Chlorothalonil 75%WP @ 0.2% 855 1321 1000 1164 1085 3.32 7.28 Carbendazim-12% + Mancozeb-63% @ 0.2% 861 1329 914 1289 1098 3.03 7.51 0.47 5 Thiophanate methyl 70% WP @ 0.2% 944 1254 942 1242 1096 2.64 7.36 0.67 6 Carbendazim 50%WP @ 0.05% 928 1399 1005 1300 1158 3.17 7.88 0.46 7 Control 827 1208 892 1100 1007 2.70 7.35 0.40 S.Em± 50.32 54 94.56 63.79 24.14 C.D. 5% NS NS NS NS 71.69 C.V. % 9.74 8.31 19.83 21.81 4.38 [Vol. 63(1) : 2010] 3 4 Indian Phytopathology [Vol. 63(1) : 2010] 65 Table 3. Economics (pooled) of the management of frog eye leaf spot of bidi tobacco with fungicides Tr. No. Treatment Details Yield kg/ha Gross income Rs/ha Cost of cultivation Rs/ha Net Income Rs/ha B:C 1 2 3 4 5 6 7 Hexaconazole 5% E.C. @ 0.1% Propiconazole 25% E.C. @ 0.1% Chlorothalonil 75%WP @ 0.2% Carbendazim-12% + Mancozeb-63% @ 0.2% Thiophanate methyl 70% WP @ 0.2% Carbendazim 50%WP @ 0.05% Control 1121 1146 1085 1098 1096 1158 1007 39235 40110 37975 38430 38360 40530 35245 18700 19420 19828 19204 20020 18280 18000 20535 20690 18147 19226 18340 22250 17245 1:2.09 1:2.06 1:1.91 1:2.00 1:1.91 1:2.21 1:1.95 with respect to plant hight,leaf length and leaf width in individual years and on pooled basis, the application of new molecules indirectly supported which resulted in significant reduction in disease pressure and improvement in yield (Table 1). Among the quality parameters % nicotine ranged from 2.64 to 3.56. Management of disease with triazoles and other fungicides significantly increased the % nicotine which is the indicator of good quality tobacco*(Table 2). The % reducing sugars ranged from 7.17 to 7.88%. Maximum % reducing sugar was noticed in Carbendazim (7.88%) followed by Carbendazim + Mancozeb (7.51%).The chlorides % was within the limit of <1 in all the treatments. The economic analysis revealed maximum net income (Rs.22,250/ha) in carbendazim with B:C ratio of 1:2.21.The assessment of triazole molecules for economics recorded net income of Rs. 20690 and Rs. 20535 per ha with B:C ratio of 1:2.06 and 1:2.09 in propiconazole and hexaconazole respectively. Minimum net income (Rs.17, 245/ha) with B:C ratio of 1:1.95 was obtained in untreated check (Table 3). The present field level investigations were further tested on large scale basis at farmer’s field’s revealed superiority of triazoles over positive check. The earlier reports of Wajid et al. (1986) in C.nicotianae of FCV tobacco and Reddy et al. (1992) in burley tobacco nursery opined effectiveness of carbendazim @ 0.04%. Hundekar et al. (2005) also reported effectiveness of carbendazim in bidi tobacco. The present findings demonstrated the practical utility of triazole as effective component in Integrated Disease Management strategy to cater the needs of farming community and to delay the resistance development by different strains of C.nicotianae in India. Thus, it can be concluded that spraying with hexaconazole @0.1% or propiconazole@0.1% or carbendazim@0.05% twice at 15 days interval be recommended as effective field level management strategy for frog eye leaf spot to produce excellent quality of bidi tobacco (Nicotiana tabacum) in India. REFERENCES Anonymous (1978). Annual Report. All India Co-ordinated Research Project (AICRP) on Tobacco. New Delhi. pp. 333334. Hundekar, A.R.,Jahagirdar, Shamarao, Matiwade, P.S. and Bhat, B.N. (2005). 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