STUDIES ON THE EFFECT OF VARIATION IN SOWING DATES ON THE INCIDENCE OF CHICKPEA INFESTATION BY POD BORER HELICOVERPA ARMIGERA (HURNER) ITS BIOLOGY AND NEEM BASLD BOTANICALS MANAGEMENT IN LABORATORY

Abstract

The present study was conducted to evaluate the effects of variation in sowing dates on chickpea, its biology and influence of neem based botanicals for the management of the pest under laboratory condition in experimental field of Sher-e-langla Agricultural University, Dhaka during Rahi 2007-2008. The sowing date was considered as treatment to find out the incidence and damage severity of pod borer in chickpea during the growing season. They were T1: Sowing on 10 November' 07; T: Sowing on 20" November' 07; T3: Sowing on 30" November' 07; T4: Sowing on December' 07' 15: Sowing on 20h December' 07; 15: Sowing on 30" December' 07. On the other hand application of Neem based botanicals were considered as treatments of the experiment which were: T: Spraying with neem oil @ 0.5% + trix 5gm; T2: Spraying with neem oil @31.0% + trix 5gm; T3: Spraying with neeni oil 1.5% ± trix 5gm; T. Sprayirg with neem seed kernel extract Ca,0.5% + trix 5gm; T: Sprayirg with neem seed kernel extract @ 1.0% trix 5gm; T: Sprayirg with neem seed kernel extract 1.5% ± trix 5gm; 17. Spraying with necm leaf extract Cz, 50m] + trix 5gm and T8: Untreated control. The average length and breadth of the eggs was 0.45 ± 0.003 mm and of 0.4$ ± 0.004 mm with the average incubation period of 3.50 ± 0.15 days. The He/icorerpa anni,gera (Hubner) larva has six instars. The average length and breadth of pre-pupal stage was 20.40±0.42mm and 4.37 ± 0.18mm with average pre-pupal period of 1.89 ± 0.12 days. In case of male pupa the average length and breadth was of 15.7 ± 0.28 mm and 2.51 ± 0.08 mm. again, in female it was 16.8 ± 0.26 mm and 3.31 ± 0.11 mm. At early fruiting stage, the highest percent of pod infestation per plant (43.14%) was found in the treament 15 and the lowest (17.53 in the treatment T1. At mid fruiting stage, the highest percent of pod infestation (52.35%) per plant was found in the treatment T4 and the lowest (25.6 1%) was found in the treatment T1. At late fruiting stage, the highest percent of pod infestation (58.52%) per plant was found in the treatment T6 and the lowest (30.59%) in the treatment T1 . In temis of yield, the highest yield (1538 kg/ha) was recorded in the treatment T2 and the lowest (750 kg/ha) was recorded from the treatment Ti,. The highest pre-weight (3.35 m(T) of full fed larva was recorded in the treatment T3 and the lowest (3.03 m(y) of in the treatment 13. The highest total life span (32.23±0.31) was recorded in the treatment T5, while the lowest (21.28±0.23) from 13. In case of the lanal cumulative mortality for chickpea pod borer larva treated with different neem based botanicals the highest percentage (20.33%) of morality was recorded from the treatment component '1'3, whereas the lowest (3.00%) was recorded in T8. Considering the antifeedant effect of different botanicals on chickpea pod borer larva in case of larval cumulative mortality the highest percentage (I I.67%) of morality was recorded in the treatment Ti, whereas the lowest (2.00%) was recorded in T.