Population dynamics of rice hispa Dicladispa armigera (Olivier) in Barak Valley of Assam and effectiveness of bio-pesticides for its management

Population dynamics of Dicladispa armigera (Olivier) was studied in two sites of Barak valley of Assam, viz., Dargakona and Katigarah in three seasons (Amon, Boro, Aus) for two years (2003–2005). Maximum population was recorded on Ranjit variety (15.2 ± 2.31 nos./5 sweeps) on 1^st week of October, 04 followed by 12.2 ± 1.67 nos./5 sweeps, on 3^rd week of September, 04 during Amon seasons in Katigarah. Kala birane variety showed maximum population (4.4 ± 0.32 nos./5 sweeps) on 1^st week of September, 03. Whereas Dargakona witnessed maximum population (6.4 ± 0.14 nos./5 sweeps) on Ranjit Variety during the 3^rd week of October, 04 followed by 1^st week of October, 04 where population was recorded to be 5.8 ± 0.14 nos./5 sweeps. Bio-effectiveness was studied for two years with two bio-pesticides viz. Calpaste and Larvocel where Larvocel (0.1%) afforded maximum (86.38%) mortality of insect-pests after seven days of application during second year. All the treatments proved to be significant (p<0.05) over control (water spray). Toxicity persisted upto ten days after application.