Indian Phytopath. 56 (3) : 266-269(2003)

Management of stem rot of rice with resistance inducingchemicals and fungicides

A. KUMAR, RAM SINGH1 and B.L. JALALIDepartment of Plant Pathology, Choudhary Charan Singh Haryana Agricultural University, Hisar 125 004

ABSTRACT: The efficacy of resistance inducing chemicals and fungicides against stem rot of rice wasevaluated in a field experiment. Of the six resistance inducing chemicals, benzoic acid was found better overother chemicals in reducing the stem rot incidence and severity followed by naphthalene acetic acid.Amongst nine fungicides, propiconazole was found most promising and provided 47.5 per cent and 26.5 percent reduction in disease incidence and severity, respectively along with 7.7 per cent increase in grain yieldfollowed by isoprothiolane. Three sprays of propiconazole at disease initiation, boot and flowering stagesprovided maximum disease control along with significant increase in grain yield followed by two sprays atdisease initiation and boot stages. The effective fungicides provided better disease control as compared toresistance inducing chemicals.

Key words: Fungicides,resistanceinducingchemicals,rice, Sclerotium oryzae, stem rot

Stem rot caused by Sclerotium oryzae Catt.(=Magnaporthe salvinii (Catt.) Krause andWebster) is one of the major limiting factors inrice cultivation in the state of Haryana. All thecultivated varieties suffer from this disease. Thedisease affects the stem resulting in rotting andsubsequent lodging of the crop. Since resistanceto stem rot in rice genotypes is rare (Raina et al.,1980; Chand et al., 1985), management of thedisease through chemicals becomes imperative.Although control of stem rot through fungicideshas been examined (Singh et al., 2002), inductionof host resistance through chemicals has notreceived attention. The present study was,therefore, undertaken to evaluate certainresistance inducing chemicals and fungicidesunder field conditions for management of stem rotof rice along with developing a spray schedule ofmost promising fungicide.

MATERIALS AND METHODS

Evaluation of resistance inducing chemicals

A field experiment was conducted during kharif1999 and 2000 at CCS HAU Rice Research

1 CCSHAURice ResearchStation, Kaul 136 021

Station, Kaul in a randomized block design withthree replications using Jaya as test cultivar. Allthe recommended agronomic practices werefollowed to raise the crop. Nitrogenous fertilizerwas applied at 150 kg N/ha and the soil was keptsubmerged to make the crop prone to the disease.Six resistance inducing chemicals viz. salicylicacid (Central Drug House) at 0.1%, 2,4-D EthylEster (Northern Minerals Ltd.) at 0.1%, kinetin(Central Drug House) at 0.01%, naphthalene aceticacid (Central Drug House) at 0.1%, benzoic acid(Central Drug House) at 0.1% and acibenzolar-S-methyl manufactured as Bion (Ciba Geigy) at0.05% were sprayed individually at diseaseinitiation and repeated once at flowering stage ofthe crop. The observations were recorded ondisease incidence (Anonymous, 1988) and diseaseseverity (Krause and Webster, 1973) on arandomly selected set of 25 hills per plot at thetime of maturity. The grain yield of paddy wasrecorded on plot basis (4 x 3 m) and expressedas q/ha.

Evaluation of fungicides

Nine fungicides viz. propiconaz.ile (Tilt 25

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EC), mancozeb (Indofil M-45 75 WP),hexaconazole (Contaf 5 EC), chlorothalonil(Kavach 75 WP), iprobenphos (Kitazin 48 EC),carbendazim (Derosal 50 WP), thifluzamide (Pulsor2F), isoprothiolane (Fuji one 40 EC) andthiophanate-methyl (Topsin-M 70 WP) wereevaluated in a field trial conducted in randomizedblock design during kharif 1998 and 1999 using asusceptible cultivar Jaya (Table 2). Thefungitoxicants were sprayed at disease initiationand repeated once at flowering stage of the crop.The plot sprayed with water served as check. Thedisease incidence, disease severity and grainyield of paddy were recorded as stated earlier.

Spray schedule of propiconazole

Spray schedule of the most effective fungicideviz. propiconazole was worked out by spraying itonce, twice and thrice at different crop (cv. Jaya)growth stages in a field trial laid out in randomizedblock design during kharif 1999 and 2000 (Table3). Observations on disease incidence, diseaseseverity and grain yield were recorded asmentioned above.

RESULTS AND DISCUSSION

Evaluation of resistance inducing chemicals

Amongst six resistance inducing chemicalstested, benzoic acid was the most effective overother chemicals followed by naphthalene aceticacid in.reducing the disease incidence and severity(Table 1). Based on mean of two years data,

Indian Phytopathology 267

benzoic acid reduced stem rot incidence to 61%as against 74% in the check. However, it had nosignificant effect on disease severity. Naphthaleneacetic acid has also been reported to reduceVerticillium wilt of potato (Corsini et al., 1989) andFusarial wilt of tomato (Corden and Dimond, 1959)through induction of host resistance. Kinetin hasbeen found to stop the development of haustoriaof Erysiphe cichoracearum in cucumber (Dekker,1963). Bion 50WG reduced the incidence ofAlternaria macrospora on cotton by 43-87%(Colson et al., 1998) while 2,4-dicholorophenoxyacetic acid was found effective against root rot ofpeanuts caused by Pythium myriotylum throughtheir effects on root lipids and root lipid exudationpatterns (Hale et al., 1981). Salicylic acid hasbeen shown to be a signaling molecule involvedin both local defense reactions at infection sitesand the induction of systemic resistance (Durneret al., 1997). However, in the present studies,2,4-0, Bion, kinetin and salicylic acid had noeffect on stem rot of rice.

Evaluation of fungicides

Edifenphos, carbendazim, DBP, benomyl,isoprothiolane and thiophanate-methyl have beenfound very effective in managing stem rot (Singhet al., 2002). Superiority of benzimidazoles(benomyl and carbendazim) over otherfungitoxicants (Dithane Z-78, Demosan, Difolatan,Hinosan and Dithane M-45) in managing stem rothas also been reported by Kasirajan and Prasad,1976; Chien, 1977 and Singh et al.,1988. In the

Table 1. Effect of resistance inducing chemicals on stem rot incidence and grain yield of paddy cultivar Jaya

Chemical Dose Disease incidence (%) Disease index (1-5) Yield (q/ha)(%) 1999 2000 Mean 1999 2000 Mean 1999 2000 Mean

Salicylic acid 0.1 63.5 (52.8) 76.8 (61.2) 70.1 1.82 2.34 2.08 77.6 77.1 77.32,4-D 0.1 72.5 (58.4) 72.9 (58.6) 72.7 2.11 2.30 2.20 79.6 70.4 75.0Kinetin 0.01 70.9 (57.4) 74.2 (59.5) 72.5 2.06 2.30 2.18 75.4 73.7 74.5NAA 0.1 67.5 (55.2) 63.4 (52.8) 65.4 1.73 2.12 1.92 72.8 76.8 74.8Benzoic acid 0.1 59.9 (50.4) 63.9 (53.1) 61.1 2.01 2.07 2.04 78.0 78.2 78.1Bion 0.05 70.9 (57.4) 72.3 (58.2) 71.6 2.14 2.37 2.25 79.3 76.3 77.8

Check 74.5 (59.7) 73.4 (58.9) 73.9 2.09 2.19 2.14 77.2 72.8 75.0

LSD 5% 1.4 1.5 N.S N.S 1.3 1.5

NAA: Naphthelene acetic acidFigures in parentheses indicate angular transformed values

present study, field trials showed that all the testfungitoxicants significantly reduced the diseaseincidence over check. During kharif 1998,propiconazole was the most effective and reducedthe disease incidence to 29 per cent compared to61 per cent in untreated check followed byisoprothiolane. Thifluzamide was least effective.During kharif 1999, hexaconazole was the mosteffective and reduced the disease incidence to 37per cent as against 75 per cent in untreatedcheck followed by propiconazole andisoprothiolane while chlorothalonil was the leasteffective in reducing the disease incidence. Basedon mean of two years data, propiconazole wasthe most promising in reducing the disease

Table 2. Effect of fungicides on stem rot incidence and grain yield of paddy cultivar Jaya

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incidence followed by isoprothiolane andhexaconazole while thifluzamide and chlorothalonilwere the least effective (Table 2).

In general, grain yield was significantly higherin fungicide treated plots excepting carbendazimduring kharif 1999 while during kharif 1998 asignificant increase in grain yield was recorded inisoprothiolane, carbendazim and thiophanate-methyl treated plots. On average basis,propiconazole and isoprothiolane treated plotsrecorded maximum grain yield followed bythifluzamide, while the lowest average grain yieldwas recorded in mancozeb treated plots (Table2).

Fungitoxicant Dose (%) Disease incidence (%) Disease index (1-5) Yield (q/ha)1998 1999 Mean 1998 1999 Mean 1998 1999 Mean

Propiconazole 0.1 29.1 (32.6) 42.2 (40.5) 35.6 1.58 1.59 1.58 62.2 87.7 74.9Mancozeb 0.25 48.1 (43.9) 61.4 (51.6) 54.7 2.13 2.02 2.07 61.9 80.6 71.2Hexaconazole 0.2 47.4 (43.5) ,. 36.9 (37.5) 42.1 1.97 1.53 1.75 61.9 81.4 71.6Chlorothalonil 0.1 51.8(46.1) 70.4 (57.1) 61.1 2.27 1.98 2.12 62.4 81.4 71.4

Iprobenphos 0.1 48.8 (44.5) 57.4 (49.3) 53.1 2.14 2.01 2.07 61.9 84.0 72.9Carbendazim 0.1 44.9 (42.1) 47.2 (43.4) 46.1 2.11 1.60 1.85 67.5 76.1 71.8Thifluzamide 0.1 55.6 (48.3) 68.9 (56.1) 62.2 2.25 1.95 2.10 63.0 84.5 73.7Isoprothiolane 0.1 36.6 (37.2) 44.1 (41.6) 40.3 1.74 1.60 1.67 68.2 81.2 74.7Thiophanate-methyl 0.1 44.6 (41.9) 54.3 (47.5) 49.4 2.07 1.84 1.95 64.4 80.8 72.6Check 60.7 (51.2) 74.9 (59.9) 67.8 2.22 2.09 2.15 61.8 77.2 69.5

LSD 5% 1.6 1.4 0.6 0.9 1.6 2.7

Figures in parentheses indicate angular transformed values

Table 3. Effect of spraying propiconazole at different crop growth stages on stem rot and grain yield of paddycultivar Jaya

Stage of Disease incidence (%) Disease index (1-5) Yield (q/ha)spraying 1999 2000 Mean 1999 2000 Mean 1999 2000 Mean

Disease initiation (01) 52.1 (46.2) 38.0 (38.1) 45.0 1.9 1.8 1.9 73.8 84.6 79.2Booting (B) 46.2 (42.8) 40.0 (39.2) 43.1 1.7 1.6 1.7 73.0 85.5 79.2Flowering (F) 46.1 (42.8) 30.7 (33.6) 38.4 1.7 1.4 1.6 75.6 82.8 79.201 + B 23.1 (28.7) 22.2 (28.1) 22.6 1.3 1.4 1.4 75.1 83.0 79.001 + F 32.6 (34.8) 36.9 (37.2) 34.7 1.5 1.7 1.6 76.1 85.1 80.6B + F 26.2 (30.8) 20.3 (26.8) 23.2 1.4 1.4 1.4 78.0 82.8 80.4

01 + B + F 20.7 (27.1) 19.7 (26.4) 20.2 1.3 1.3 1.3 81.7 86.8 84.2Check 74.9 (59.9) 73.4 (59.3) 74.1 2.1 2.2 2.2 77.2 72.8 75.0LSD 5% 3.1 5.3 0.3 0.4 3.1 1.5

Figures in parentheses indicate angular transformed values

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Spray schedule of propiconazole

The average data of kharif 1999 and 2000indicated that the disease incidence and severitywas minimum in plots sprayed thrice at diseaseinitiation (maximum tillering stage), booting andflowering stage of the crop followed by plotsreceiving two sprays at disease initiation and atbooting which were statistically at par (Table 3).On average basis, plots sprayed thrice duringdisease initiation, booting and flowering stagesresulted in maximum grain yield followed by plotssprayed twice either at disease initiation andflowering or at booting and flowering stages.Application of carbendazim at disease initiationand booting stage proved more effective thancorresponding sprays of isoprothiolane in reducingstem rot (Sunder et al., 1991). It was concludedthat application of two to three sprays ofpropiconazole are required for effectivemanagement of the disease.

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Received for publication February 3, 2003