Management of root-knot nematode, Meloidogyne sp. (Kofoid and White) in Coleus, Solenostemon rotundifolius(Poir) morton

Abstract

The study entitled ‘Management of root-knot nematode, Meloidogyne sp. in coleus, Solenostemon rotundifolius (Poir) Morton’ was conducted at College of Horticulture, Vellanikkara during 2012-2013 with the objectives of assessment of the population of plant parasitic nematodes infesting coleus at different coleus growing regions of Thrissur District, identification of the species of Meloidogyne infesting coleus and evaluation of biocontrol agents, organic amendments and a chemical insecticide against this root- knot nematode in coleus. Survey was conducted in the major coleus growing areas of Thrissur District, namely Mundathikode, Wadakkanchery, Varavoor, Thirur, Kolazhi, Vellanikkara, Madakkathara and Vadanapilly. Soil and tuber samples were collected from these localities and the nematodes were extracted to assess the population of plant parasitic nematodes associated with coleus. It was found that root-knot nematode was the major problem in all the eight locations and the species of root-knot nematode was identified as Meloidogyne incognita (Kofoid and White) Chitwood, 1949 on the basis of perineal pattern of white females. Other plant parasitic nematodes recorded from soil samples were reniform nematode (Rotylenchulus reniformis Linford and Oliveiria), burrowing nematode (Radopholus similis (Cobb, 1893) Thorne, 1949), lance nematode (Hoplolaimus sp.), spiral nematode (Helicotylenchus sp.) and rice-root nematode (Hirschmanniella oryzae Luc and Goodey, 1963) which were not harmful to the tubers of coleus. The highest average root-knot nematode population was recorded from Kolazhi with 450.4 nematodes/ 200g soil with a gall index of 3.9. Pot culture experiment was carried out to evaluate the efficacy of biocontrol agents, organic amendments and a chemical insecticide against root-knot nematode infesting coleus. The results showed that application of organic amendments namely whole plant of Tagetes erecta, leaves of Chromolaena odorata and neem cake resulted in the enhancement of plant growth characters and resulted in a reduction of root-knot nematode population. Incorporation of T. erecta whole plant ranked first among the organic amendments. Neem cake, cartap hydrochloride 4G and combination treatments of Bacillus subtilis + Pseudomonas fluorescens and P. fluorescens + Paecilomyces lilacinus improved the yield of coleus plants. Soil application of P. lilacinus, cartap hydrochloride 4G and incorporation of T. erecta suppressed the nematode population in soil, root and tuber respectively. Combination treatment of P. fluorescens + P. lilacinus and application of neem cake also reduced population buildup of nematode and kept the infestation at a lower level. Highest reduction in number of females, number of root knots and root knot index was also observed in T. erecta and was followed by P. lilacinus, P. fluorescens + P. lilacinus, neem cake and C. odorata. The study clearly indicated that application of organic amendments and biocontrol agents were found to be as effective as cartap hydrochloride 4G in managing the root-knot nematode population in coleus and can be considered as alternative to nematicide application.