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 1st week of October, 04 followed by 12.2 ± 1.67 nos. / 5 sweeps, on 3rd week of September, 04 during Amon seasons in Katigarah. Kala birane variety showed
maximum population (4.4 ± 0.32 nos. / 5 sweeps) on 1st week of September, 03. Whereas Dargakona witnessed maximum population (6.4 ± 0.14 nos. / 5 sweeps) on Ranjit Variety during the 3rd week of October, 04 followed by 1st 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 up to ten days after application.