Toxicity and Behavioural Modification on Blackgram Leaffolder, Anticarsia irrotata Fab., (Noctuidae; Lepidoptera) Due to Wild Indigo, Tephrosia purpurea L.

Abstract

Bio efficacy of ethanol and n-hexane leaf extracts of wild indigo, Tephrosia purpurea L. was evaluated against second instar larvae of bengal gram leaffolder, Anticarsia irrorata under laboratory condition using leaf disc and topical method. The results of in-vitro study was validated under field conditions too. In leaf disc method, the second instar larvae were allowed to feed on the treated leaves while in topical application, the treatments were sprayed directly over the insects. Observations were recorded up to 3 days at 12 h interval. Observation on weight reduction of surviving larvae over control was analyzed. In leaf disc method, the mean mortality ranged from 8.33 per cent to 49.8 per cent with the highest mean mortality (41.1%) at 5% ethanol extract. Maximum reduction in weight was seen at 5 % conc. with 70.4 per cent followed by 64.7 per cent and followed by 55.3 per cent with 3 and 1% respectively. Similarly, when the effect of n-hexane extract was considered, the highest mean mortality of 41.6% against the second instar was seen at 5% conc. however, ethanol extract showed maximum mortality at 5% than n-hexane extract. Similarly, the maximum reduction in weight was seen at 5 % conc. with 65.4 per cent followed by 53.8 and 45.5 per cent at 3 and 1 % conc. Respectively. Similarly, when topical method was considered, 5% n-hexane extract of T. purpurea effected highest mean mortality (24.9%) however, the mortality rate was reduced compared to leaf disc method. Minimum mean mortality was recorded in control (8.33%) irrespective of the bioassay methods. Maximum reduction in weight was seen in at 5 % conc. with 83.5 % followed by 74 and 68.2 % with 3 and 1% conc. respectively. The maximum reduction in weight was seen at 5 % conc. with 80.4 per cent followed by 71.8 and 56.5 per cent at 3 and 1 % conc. respectively.