MSC

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.