Effect of Bacillus thuringiensis and leaf extracts of Parthenium hysterophorus,
Calotropis procera Azadirachta indica on Bihar Hairy Caterpillar, Spilosoma obliqua Walker .
V.P.S. Chahal¹, Gurdip Singh² and P.P.K Chahal³, Department of Microbiology¹, Entomology² and Plant Pathology², Punjab Agricultural University ,Ludhiana, Punjab, India<

Bihar hairy caterpillar, Spilosoma obliqua Walker is very serious pest due to its wide host range. The present Investigation reports on the effectivity of new isolates of B. thuringiensis and leaf extracts of weeds and Azadirachta indica in controlling S.obliqua Walker.

Dead larvae of Bihar hairy aterpillar were colected from the fields of sunflower for isolation of biocontrol agents, Using nutrient agar medium (Beef extract -1.0g:Yeast extract-2.0 g: Peptone-5.0 g: NaCI-0.5 g: thuringiensis were Isolated, purified and characterized. These were multiplied in nutrient broth at 28+ 1 C for 7 days on a rotary shaker. The test concentration of the inoculum was 18x 107 colony forming units/ml. Leaf extracts of congress grass (Parthenium hyterophorus), akk (Calotropis procera ) and neem (Azardirachta indica) used in the experiment have also shown to cause inhibition in the emergence of juveniles from egg masses of M. incognita.

Newly hatched larvae of S. obliqua were reared in the glass jars in the laboratory for evaluation of bacterial isolates and Leaf extracts. Second generation disease free fourth and fifth instar larvae were used for the bioassay and these were fed on the fresh green treated leaves of MSFH-8hybrid of sunflower. The leaves were washed with sterile distilled water and then sprayed with suspension of B.thuringiensis isolates or with leaf extracts of congress grass., akk and neem. An untreated control was also maintained. Fresh leaves were provided to the larvae after every 25 hours. In each replication 10 larvae were allowed to feed on the treated leaves in separate jars. All the treatments were replicated thrice. Observations on the symptoms and mortality of larvae were recorded after every 24 hours.

Both the isolates of B. thuringiensis caused infection on fourth and fifth instar larvae of S. obliqua Walker. The infected larvae turned pale yellow and black. On the contrary, healthy larvae of both the isolates of B. thuringiensis gave 100% mortality of al. (1998) have also reported 100% mortality in the larvae of cabbage semilooper due to bacterial Infection . Leaf extracts of congress grass, akk and neem caused up to 60% 50% and 70% mortality of the grown up larvae , respectively within24 to 48 hours of feeding.

References Battu, G.S. Bindra, O.S. and Rangarajan, M. 1971. Indian J.Ent., 33(3), 317-325. Chahal, P.P.K. Singh , J. Singh, G. and Chahal, V.P.S. 1998. Indian J. Ecol., 25(2), 190-191. Venkatraman, T.V. Mathur, V.K. and Rao V.P. 1963. Indian J.Ent.,25(1) ,33-35

[Courtsey:Insect Environment,Vol.9(3).Oct-Dec.2003,112-113]