(J. Bioi. Control, 22( 1): 221-224, 2008 ) Research Note Management of sorghum army worm, Mythimna separata (Walker) (Lepidoptera: N octuidae) using biopesticides SHEKHARAPPAandR.K.PATIL Sorghum Research Scheme, MARS, University ofAgricultural. Sciences, Dharwad - 580005, Karnataka, India. E-mail: [email protected] ABSTRACT: A field experiment was conducted for two years (2002-03 and 2003-04) to manage armyworm, Mytllimlla separata (\Valker), on sorghum with biopesticides, viz., Nomllraea riley; (Farlow) Samson and MsNPV. and compared with poison bait and chemical control. Spray of N. rileyi at both the doses, viz., lxlO' and 2xlO' conidia I", were found to be effective in checking the larval population. The highest yield of 21.14 q ha" was obtained in N. rUey; spray at 2xlO' conidia I" and was on par with N. riley; spray at hIO' conidia I". The maximum cost­ benefit ratio of I: 36.45 was obtained in N. riley; spray at hIO' conidia ,., followed by N. riley; spray at 2x 10' conidia I" with a CB ratio of I: 29.44. KEY WORDS: Armyworm, cost-benefit ratio, Mythimna separata. MsNPV, Nomuraea rile vi, sorghum The armywonn, Mythimna separata (Walker) users whenever it is required. Perusal ofliterature (Lepidoptera: Noctuidae), is polyphagous and one revealed that there is no work on armywonn with ofthe serious pests of cereal crops, mainly sorghum, Nomuraea riley; (Farlow) Samson. However, its maize and sugarcane in Karnataka (Kulkarni and natural epizootics on Mythimna (Pseudaletia) Jotwani, 1978). Severe epidemics of this pest unipuncta (Haw.) in rice ecosystem have been resulted in up to 100 per cent damage in transitional reported in India by Arnbethgar and Kumaran (1998). belt during 1988-89 (Anonymous, 1989) at Dharwad The natural incidence of Nomuraea rileyi on with a maximum population of35 larvae per plant Helicoverpa armigera (Hubner) and Spodoptera on sorghum. The present management strategies litura (Fabricius) was reported by PatH (2000) in aim at only use of chemical insecticides (Hiremath groundnut ecosystem at Dharwad. This et al., 1990), which pose a threat to human beings, investigation deals with the management of this domestic animals and wildlife by causing pest with biopesticides. environmental pollution. Apart from this, application of chemicals in tall crops like sorghum is hazardous The experiment was conducted at University to the applicator. Hence, a study was made to of Agricultural Sciences, Dharwad, during 2002 - evaluate biopesticides as they are ecofriendly, 2004 on sorghum (Var: CSH-9) raised in 11 rows, effective, mass multiplied under laboratory each 4m long spaced at 45cm. Each row consisted condition, stored and made available to the end of 27 plants. The plot size of each treatment was SHEKHARAPPA and PATIL 5.4mx4m. The crop was protected from all pests and towards the management of armyworm were diseases by following the recommended plant calculated. Based on this, the cost-benefit ratio was protection schedule except for armyworm. Soil worked out. application of carbo fur an 3G @30 kg ba" was done at the time of sowing for the management of shoot There was no significant difference among fly. The experiment was laid out in completely the treatments before imposing the treatments randomized block design comprising five treatments indicating the uniformity in pest pressure and five replications. The facultative fungus N. during both the years. The number of larvae per rileyi was tested for its pathogenicity to M. plant after spray was least in the treatment N. rileyi separata at two dosages, viz., I x I Os conidia I-I and (2x I OR conidia 1'1), followed by spray of 2x I Os conidia 1. 1 and compared with MsNPV 250LE N. rileyi @ 1 x I 0 8 conidia 1'1 (during 2002-03). ha- ', poison bait (50 kg rice bran, 2 kg jaggery, However, these two treatments were on par 250mlmonocrotophos and 61 of water per hectare) with each other. The treatments MsNPV @ and endosulfan @ 0.07% spray under field 250LE ha'l and poison bait recorded 0.83 and 0.81 condition. The treatments were imposed only once larvae / plant, respectively, and were found to be at 50-55 days after sowing. Observations were made equally effective in the management of on the number oflarvae per plant a day before and M. separata, but differed significantly from 10 days after application. The data were subjected N. rileyi sprays at both the dosages and also to statistical analysis after square root chemical control by endosulfan spray transformation (x+ I). The data on yield was noted (0.07%). During 2003-04, N. rileyi sprays at from each treatment and finally cost-benefit ratio both the dosages emerged as the best treatments was worked out. The gross return, net return and by recording the least number of larvae the actual expenditure made in each treatment per plant. These two treatments were found to be Table 1. Management of Mytltinma separata using biopesticides Treatment No. of larvae I plant Before spray After spray 2002-03 2003-04 2002-03 2003-04 Mean Spray N. rileyi @ 1x I ORconidia ,-I 2.71" 2.61 ' 0.6P 0.57" 0.59" ( 1.92) ( 1.90) ( 1.26) (1.25) (1.26) Spray N. riley; @ 2x 108conidia 1-' 2.80a 2.68" 0.56" 0.50" 0.53' ( 1.95) (1.91) (1.24) ( 1.22) ( 1.23) MsNPV @ (250LE ha-') 2.74" 2.64" 0.83h 0.78" 0.81b (1.93 ) (1.90) ( 1.35) (1.33) (1.34) a a Poison bait 2.75 2.65 0.81 b O.77b 0.79" ( 1.93) ( 1.91) (1.34 ) (1.33 ) (1.33) Endosulfan @ (0.07%) 2.81 a 2.69" 0.75" 0.70b 0.72\> (1.95) ( 1.92) (1.32) ( 1.30) ( 1.31 ) * Means followed by the same alphabet do not differ significantly (P = 0.05) by DM RT; figures in parentheses are square root transformed values (x+ I) 222 Management of Mylilimna separata using bio-pesticides Table 2. Yield and cost benefit ratio of biopesticide treatments for the management of M. separata Treatment Yield q Iha C: B ratio 2002-03 2003-04 Mean Spray N. rileyi @ I x )-1 108 conidia 25.12" 15_02' 20.07" ,. 1: 36.45 Spray N. rileyi @ 2 x I 08conidia I-I 25.22' 15.05' 20.14' 1:29.44 I b MsNPV @(250LE ha- ) 23.351> 13.331> 13.35 1:6.82 Poison bait 23.15b 13.14b 18.15b 1:9.53 Endosulfan @ (0.07%) 25.03a 14.85' 19.95" 1: 10.68 * Means followed by the same alphabet do not dilTer significantly (P = 0.05) by DMRT; figures in parentheses are square root transformed values (x+l) on par with each other and differed significantly REFERENCES from the rest of the treatments. The pooled analysis over two years indicated a similar trend Ambethgar, V. and Kumaran, K. 1998. Incidence of green (Table 1). muscardine fungus, NOllluraea rileyi (Farlow) Samson on Spodoptera litura (Fabricius) in soybean, Glycine max (L.) Merrill from Tamil Nadu (lndia)_ The mean maximum yield of 20_I4q ha- 1 Journal ofEntomological Research, 22: 195-196. over two years was obtained by the application of N. rileyi @ 2x 10& conidia 1-1, closely followed Anonymous, 1989. Anllual progress report. All India by N. rUeyi 1x 10 8 conidia )-1, both on par with Co-coordinated Sorghum Improvemellt Project. each other. These two treatments out yielded Dharwad Centre for the year 1988-89, p.24. and differed significantly from the rest of the treatments. Maximum C: B ratio of 1: 36.45 Hiremath, I. G., Bhuti, S. G., Kachapur, M. D., Viraktamath, S. and Lingappa, S. 1990. Mass killing was obtained with N. rileyi @ 1xl 08 conidia 1-1, of moths - A new approach in the management of 8 followed by N. rileyi @ 2x 10 conidia 1-1 (1: 29.64) armyworm, Mythimna separata (Walker). Karnataka (Table 2). Journal ofAgricultural Sciences, 3: 128-130. These findings are in close agreement with Ignoffo, C. M. 1981. The fungus Nomuraea rileyi as a the findings ofPatil (2000) who also reported that microbial insecticide, pp. 513-536. In: Burgess, H. S. fitura could be suppressed by the application of D. (Ed.), Jvfjcrobial Control of Pests alld Plant N. rileyi with increased yield in groundnut. Similarly, Diseases. Academic Press, New York. N. rileyi was reported to be capable of causing spectacu lar epizootics in caterpi lIar pests of Kulkarni, K_ A. and Jotwani, M. Q 1978. Screening of cabbage, clover, soybean (lgnoffo, 1981), promising entries to the armyworm, Mythimna groundnut, castor, potato, cotton, etc. (PatH et aI, separata (Walker). Sorghum Newsletter, 21: 36 2003, Manjula et ai., 2003, 2004). 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Journal ofEntomological the management of Spodoptera litura (Fabricius) Research, 22: 109-113. (Received: 30.08.2006; Revised: 01.03.2007; Accepted: 01.09.2007) 224 .