MSc

The study entitled ‘Bioefficacy of Andrographis paniculata (Burm. f.) Nees against root-knot nematode, Meloidogyne incognita (Kofoid and White) Chitwood in okra’ was conducted at Department of Nematology, College of Agriculture, Vellayani, Thiruvananthapuram during 2019-2021. The objective of the study was to find out the efficacy of solvent extracted A. paniculata dry powder on egg hatching and juvenile mortality of M. incognita under in vitro conditions and evaluation of the botanical in comparison with bioagent, organic amendment and synthetic nematicide, Fluopyram in okra.
An experiment was conducted to test the efficacy of different concentrations of acetonitrile, acetone, methanol and aqueous extracted dry powder of A. paniculata (15, 10, 5 and 1%) on egg hatch inhibition and juvenile mortality of M. incognita. The experiment was laid out in CRD with 18 treatments and 3 replications, Fluopyram 0.625 mLL-1 and distilled water were maintained as check and control. The results of the in vitro screening revealed that methanol extract 15% exhibited lowest egg hatching (0.00 to 1.18 per cent) for an exposure period of three to eight days and juvenile mortality of 92.00 to 99.33 per cent at 24 to 72 h after treatment. Based upon the ovicidal and larvicidal property, methanol extract of A. paniculata dry powder 15% was selected for the preparation of oil based formulation.
Oil based formulation was prepared by mixing the powder obtained from the concentrated methanol extract of A. paniculata with pongamia oil and surfactant Tween – 80 in the ratio 70: 15: 15. An experiment was laid out in CRD with 16 treatments and 3 replications to study the efficacy of oil based formulation of A. paniculata (0.5, 1.0, 2.0, 2.5 and 5%) in egg hatch inhibition and juvenile mortality of M. incognita. Pongamia oil (15%) + Tween – 80 (15%), Fluopyram 0.625mLL-1 and distilled water were maintained as check, chemical check and control. The results revealed that the 5% A. paniculata oil based formulation was found to be effective in inhibiting egg hatching (99.49 to 97.19 per cent) at three to eight days after treatment. A. paniculata oil based formulation 5% exhibited 82.67 to 99.33 per cent mortality of M. incognita juveniles 24 to 72 h after treatment and it was found statistically on par with chemical check.
Based on the results of in vitro screening, a pot culture study was laid out in CRD with oil based formulation of A. paniculata in comparison with bio agent (P. lilacinum), organic amendment (neem cake), chemical nematicide (Fluopyram 0.625mLL-1) and control in okra with three replications. Oil based formulation of A. paniculata (5 and 10%) was applied as soil drenching and no phytotoxicity was observed in any treatments. The results revealed that application of oil based formulation @ 10% significantly reduced nematode population in soil (80.47 per cent) and root (92.09 per cent) compared to control. Regarding number of females and reproduction factor also a similar trend was observed. Among non-chemical methods, oil based formulation of A. paniculata 10% was found to be equally effective to oil based formulation of A. paniculata 5% and P. lilacinum enriched farm yard manure (FYM) resulting in 67.69 to 89.57 per cent reduction over untreated check. Gall index in the above treatments was two against three in untreated. Effect of oil based formulation of A. paniculata 10% was statistically on par with the chemical (Fluopyram 0.625mLL-1) on growth parameters viz. plant height, number of leaves and fresh shoot weight (68.84 to 77.71 per cent increase over untreated). In the case of number and weight of fruits, oil based formulation of A. paniculata 10% was found to be statistically on par with P. lilacinum enriched FYM and chemical giving 81.81 to 91.94 per cent increase over untreated.
It can be concluded from the present study that the oil based formulation containing methanol extract of A. paniculata dry powder 15%, pongamia oil and surfactant (Tween-80) exhibited significant egg hatch inhibition and juvenile mortality of M. incognita under in vitro conditions. Soil drenching of oil based formulation of A. paniculata 10% suppressed nematode population and increased yield in okra. Hence it can be included as an eco-friendly component in integrated nematode management strategy.