Evaluation of bio-agents and pesticide on root-knot nematode development and oil yield of patchouli.

Nematode problems are increasing tremendously in arable soil due to the continuous cultivation of susceptible agricultural crops. Besides the scope of effective chemical armory to combat with, this pest is gradually decreasing. The major factor behind such a scenario is the adverse effect of chemical nematicides on human health, useful organisms, the environment as well as underground water. Therefore, effective chemical nematicides for field use may not be available in the future. Consequently, it has become inevitable to manage this pathogen through such non-chemical management tactics like fallow, flooding, changes in time of sowing/planting material, tillage practices, crop rotations, use of antagonistic crop, trap crop/cover crop, use of nematode free planting materials or seeds, solarization, organic amendment and biological control. Plant parasitic nematodes, if not checked, prove to be a major obstacle in the future prospects of medicinal and aromatic plants in India causing significant damage. Pogostemon cablin (Syn. P. patchouli) suffers greatly from infection of root-knot nematode, Meloidogyne incognita (Kofoid and White) Chitwood, resulting in a considerable reduction in oil yield. A glasshouse experiment was designed to evaluate the relative efficacy of bioagents (Glomus mosseae, Trichoderma harzianum), and a pesticide (Furadan) on reproduction and infection potential of M. incognita in P. cablin. Trichoderma harzianum enhanced the growth, biomass and oil yield of the test plant. Significant reduction in the severity of root-knot disease and population of M. incognita was recorded in the pots treated with T. harzianum when compared to the Furadan treated pots. G. mosseae also performed well but it was less effective than Furadan. It is therefore suggested that T. harzianum can be considered as a wise option instead of hazardous pesticides for reducing root-knot disease in P. cablin. [ABSTRACT FROM AUTHOR]