(J. Bioi. Control, 22(1): 209-212, 2008) Research Note

Efficacy of nucleopolyhedrovirus against ohliqua (Walker) on mulberry

K. VEENAKUMARI, R. J. RABINDRA, C~'D. SRINIVASA NAIK and M. R. SHUBHA Project Directorate of Biological Control, Post Bag No. 2491, Bellary Road, Hebbal, Bangalore - 560024, Kamataka, India. E-mail: [email protected]

ABSTRACT: Pot experiments carried out to study the efficacy of nucleopolyhedrovirus against the Bihar hairy caterpillar Spilarctia obliqua (Walker), at Bangalore indicated that a spray of NPV @ lx10' POB ml-' resulted in a larval mortality of 93.33% in third instar larvae and 87.5% in fourth instar larvae. Cent per cent larval mortality was obtained when the plants were sprayed with dichlorvos @ 2 ml 1-'. The leaf damage for viral treatments varied from 19.65 to 41.89 and 21.0 to 38.0 per cent for third and fourth instar larvae, respectively.

KEY WORDS: Mulberry, SoNPV, Spilarclia obliqua

Spilarctia obliqua (Walker) (: pesticides. Use of ecofriendly microbial pesticides Arctiidae), commonly called the Bihar hairy such as baculoviruses seems to be a viable caterpillar or hairy caterpillar, is a polyphagous alternative to ensure that environmental safety is pest attacking a variety of plants including not compromised. Jacob and Thomas (1972) for the cultivated crops. It is known to feed on more than first time reported the occurrence of a 126 plant species causing considerable losses in nucleopolyhedrovirus (SoNPV) infecting S. obliqua various crops (Singh and Varatharajan, 1999). larvae collected from sweet potato fields at However, this hairy caterpillar is attacked by a large Vellayani. Further work on SoNPV was carried out number of natural enemies (Battu et al., 1972; by several workers (Battu et al., 1996; Chaudhari, Premchand, 1979; Battu and Ramakrishnan, \989). 1997; Singh and Varatharajan, 2001). Genomic In spite of these natural enemies this pest continues studies were also conducted on SoNPV to pose a major threat to the cultivation of many (Manickavasagam et al., 1992). No attempts have crops such

conducted at the Project Directorate of Biological quantified by phase contrast microscopy (Nikon Control, Banglore, on the efficacy of this Eclipse E 400) using a double ruled improved baculovirus in controlling S. obliqua on mulberry. Neubauer haemocytometer and the virus suspension thus standardized was stored in the Late instar larvae of S. obliqua collected from refrigerator. mulberry fields ofVijayapura (Bangalore district, Kamataka) were reared in plastic tubs (25cm height Mulberry plants raised in pots were sprayed x 40cm diameter) fitted with ventilated lids on with SoNPY of different concentrations as bouquets of castor (Ricinus communis L.) leaves mentioned in Table 1. Crude sugar @ 1 per cent and at 26±2°C and RH 63± 10%. The larvae that pupated 0.1 per cent Triton 1 00 were added to the virus in silken cocoons were separated and placed in suspension which was sprayed at 1800 h. These plastic containers (21 cm height x IScm diameter) plants were enclosed in a nylon net cage. One hour lined with tissue paper. The that emerged after spraying, fifteen third instar larvae were were allowed to mate in acrylic cages (28 x 28 x released per plant. An insecticidal check was 30cm) containing bouquets of castor leaves for egg included in addition to the untreated control. laying. The moths were provided with 10 per cent Observations were taken 5, 7 and 10 days after honey solution for feeding. The eggs, laid in groups, treatment (DAT). Per cent leaf damage was were detached and placed in a plastic container. calculated (Jensen, 1977). Each treatment was Once the eggs hatched, the first instar larvae were replicated four times. Adopting the same procedure, released on castor leaves in plastic containers (21 cm one more experiment was conducted with fourth height x IScm diameter). The larvae were provided instar larvae releasing ten larvae (instead of IS) per fresh castor leaves daily. plant. Similar observations were taken as in the previous experiment. The data were subjected to Extensive field surveys were conducted for analysis of variance and means separated using the collection of S. obliqua larvae in and around Duncan's Multiple Range Test (DMRT). Bangalore on mulberry (Morus alba L.), field beans (Dolichos lablab L.), alligator weed (Alternanthera In case of third instar larvae of S. obliqua, a philoxeroides Griseb.), etc. The diseased larvae that larval mortality of93.3 per cent was recorded on 10 were found in the field were collected individually DATwhen SoNPV was sprayed @ 1 x I 07 POB mI'!. in vials and examined for possible microbial Larval mortalities for the other two concentrations pathogens in the laboratory. Virosed larvae were ofSoNPY (2xl06 and2xl

210 Nucleopolyhedrovirus against SpilarClia obliqlla on mulberry maximum larval mortality of92.5 per cent, followed could be replaced by using this virus as a biocontrol by SoNPV @ lxl07 POB ml- I (87.5 per cent). The agent under field conditions against S. obliqua. leaf damage in insecticide treated plants was 11.2 Because of the species-specific nature of per cent. It was also noticed that third instar larvae baculoviruses, parasite and predator populations were more susceptible to SoNPV than the fourth (Battu et al., 1972; Premchand, 1979; Battu and instar larvae (Table 1). Larvae ofS. obliqua are poor Ramakrishnan, 1989) of this pest win not be feeders till they cross the third instar. Once the larvae adversely affected in the field. Laboratory reach fourth instar, they become highly voracious. experiments conducted to test the cross infectivity Foliar application of the virus in the early stages of of this virus to silkworm larvae (Bombyx mori L.) larval growth will, therefore, control the pest more revealed the species specificity of this virus and its effectively. However, in case the virus application inability to infect the silkworm larvae (Veenakumari, is delayed and the larvae are in the penultimate or unpublished). The virus is also found to be safe to final instar, it will increase the virus yield. This will vertebrates such as garden lizard (Caloles Table 1. Efficacy of S. ohUqua NPV on third and fourth instar of Bihar hairy caterpillar

Treatments Third instar Fourth instar Per cent larval mortahty Per cent Per cent larval mortality Per cent Days after treatment leaf Days after treatment leaf damage damage

5 7 10 5 7 10 SoNPV @ Ix 107 POB b h b b b mI" 56.7" 88.3 ' 93.3 19.7 30.0 65.0 87.5" 24.5" SoNPV @ 2x 106 POB h mi'! 53.3" 80.0<" 83. )< 28.4' 27.5 55.0b 62.5' 34.1 c SoNPV @ 4xl05 POB mI'! 55.0h 75.0' 82.6' 41.9d 35.0b 55.0h 57.5< 48.4' Dichlorvos @2mll-! 80.0' 93.3" 100.0" 8.1' 67.5" 87.5" 92.5" 11.2" Control 5.0' 1O.0d 10.Od 89.2' 10.0' 12.5' 12.5d 97.0d

*Means followed by the same letters are not significantly different (P d" 0.05) by DMRT serve as a reservoir of the virus in the field for versicolor Fitzinger), common crow (Corvus controlling succeeding generations of the pest. In splendens Vieillot), house sparrow (Passer case the moths are formed, they will pass on the domesticus L.), mouse (Mus musculus L.) and the virus transovarially (Chaudhari, 1997). rat (Rattlls rattus Fischer de Waldheim) (Battu, 1987). It is further speculated that these vertebrates Arora et al. (1996) reported that when SoNPV might help in the dissemination ofthis baculovirus @ 250LE ha- I was used against S. obliqua in when they feed on virosed larvae, causing groundnut fields ofLudhiana, Punjab, it required a epizootics in the field (Battu, 1987). Varatharajan minimum of 5 days to obtain sufficient larval and Singh (2002) reported that this virus can be mortality. Based on this result and the encouraging easily and economically mass produced when the results obtained in the present experiments, there weed Ipomoea carnea Jacq. is used as the larval is a good possibility that chemical insecticides host plant to rear S. obliqlla for the multiplication

211 VEENAKUMARI et al.

of the virus. Alligator weed, another host plant of dissolution of occlusion bodies. Shashpa, 3: 37-45. this pest, is very common in the lakes ofBangalore. The possibility of using this weed for the Chaudhari, S. 1997. Effect of age of obliqua larvae on their susceptibility to nuclear polyhedrosis multiplication of S. obliqua for virus production virus. Indian Journal ofEntomology. S9: 59-61. should be worked out under local conditions. This virus can then be easily and economically mass Deshmukh, P. D., Rathor, Y S., and Bhattacharya, A. K. produced under local conditions. 1979. Host range of Bihar hairy caterpillar Diacrisia obliqua Walker. Bulletin ofEntomology, 17: 85-99. ACKNOWLEDGEMENTS Jacob, A. and Thomas, M. J. 1972. A nuclear \Ve thank the National Agricultural polyhedrosis virus of Diacrisia ob/iqua (Walk.). Technology Project, Indian Council ofAgricultural (Arctiidae, Lepidoptera). Agricultural Research Research, New Delhi, for financial assistance (vide JournalofKerala, 12: 82-83. FNo.28(l) 200 I-NATP/CGP-III/380) for conducting Jensen, R. L., Newsom, L. D., Herzog, D. c., Thomas, J. studies on NPVs ofarctiid caterpillars. W., Farthing, B. R and Martin, F. A. 1977. A method of estimating defol iation of soybean. Journal REFERENCES ofEconomic Entomology, 70: 240-242.

Arora, R., BaUu, 0. S., Bath, D. S. and Singh, M. 1996. Manickavasagam, S., Ramakrishnan, N., Anuradha, S. Management of Bihar hairy caterpillar, Spilosoma and Prasad, yo. 1992. Identification of three nuclear ob/iqua (Walker) with a nuclear polyhedrosis virus. polyhedrosis viruses through restriction Indian Journal ofEcology, 23: 138-140. endonuclease analysis. Journal of Biological Control, 6: 101-103. Battu,o. S. 1987. Lack of susceptibility of some vertebrate predators to five baculoviruses of the Premchand, 1979. Polyhedrosis of Diacrisia obliqua lepidopteran pests. Journal of Entomological Walker. Indian Journal ofEntomology, 41: 194. Research, 11: 184-188. Singh, Y. R. and Varatharajan, R. 1999. Host range of Battu, G. S. and Ramakrishnan, N. 1989. Comparative Bihar hairy caterpillar, (Walker) role ofvarious mortality factors in the natural control (Arctiidae, Lepidoptera). Hexapoda, 11: 65-74. of Spilosoma obliqua (Walker) in Northern India. Journal ofEntomological Research, 13: 38-42. Singh, Y. R. and Varatharajan, R. 2001. Certain aspects of NPV infecting the larvae of Spilosoma ob/iqlla Battu,o. S., Bindra, O. S. and Rangarajan, O. M. 1972. (Walker) (Arctiidae). In: Ignacimuthu, S. and Sen, Investigations on microbial infections of insect-pests A. (Eds.). Microbials in Insect Pest Management. in the Punjab. Indian Journal of Entomology, 33: Oxford IBH Publishing Co. Pvt. Ltd. 317-325. Varatharajan, R. and Singh, M.I. 2002. III vivo production Battu, G. S., Ramakrishnan, N. and Prakash, N. 1996. of Spilarctia ob/iqua (Walker) NPV. Proceedings of Electron microscopy of the nuclear polyhedrosis the Symposium on Biological COlltrol of virus of Spilosoma obliqua (Walh-r) alkali Lepidopteran Pests. July 17-18, Bangalore, India.

(Received: 27.10.2006; Revised: 26.07.2007; Accepted: 20.08.2007)

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