MSc.

The investigation entitled “Potential of natural bio polymers, chitin and
chitosan in pest management” was conducted at College of Agriculture, Vellayani
during 2016-17 with an objective to evaluate the insecticidal properties of the
natural biopolymers, chitin and chitosan for utilization in crop pest management.
Various formulations tested were, chitin (3%, 5%, 7%), chitosan (3%, 5%, 7%),
chitosan gel (3%, 5%, 7%), chitin based commercial formulation, Biorakshak 2%
and chitosan based commercial formulation, Bioboost 2%. They were tested for
their antifeedant, insecticidal, nematicidal and growth promoting properties by
leaf dip method and spray methods in laboratory as well as by foliar spray and soil
amendments in pot and field studies.
Laboratory studies revealed that the pumpkin caterpillar, Diaphania indica
Saunders, the leaf beetle Henosepilachna vigintioctopunctata F., pea aphid
Aphis craccivora Koch, the root knot nematode, Meloidogyne incognita (Kofoid
and White) Chitwood. and the reniform nematode Rotylenchulus reniformis
Linford and Oliveira were vulnerable to different chitin and chitosan based
formulations whereas, the cut worm Spodoptera litura F. the leaf weevil,
Myllocerus viridanus Schoenherr, the pod bug Riptortus pedestris F. and the
spiral nematode Helicotylenchus sp. were not. All the formulations tested were
safe to the coccinellid predators, Chilomenes sexmaculata F. and
Coccinella transversalis F., the syrphid predators, Ischiodon scutellare F. and
Xanthogramma scutellare Thorell. and the spiders Tetragnatha mandibulata
Walckenaer and Tetragnatha maxillosa Thorell. Antifeedant effect was noticed
only D. indica, chitosan 7% being the superior formulation with 43.25 per cent
feeding inhibition on first day which decreased to 13.30 per cent on the fourth
day. Insecticidal activity was noticed in H. vigintioctopunctata, chitosan gel 7%,
being the best treatment causing 100 per cent mortality on seventh day, followed
by Bioboost 2% (93.33 per cent mortality). In A. craccivora, chitin 7% caused
100 per cent mortality on fifth day while Biorakshak 2% recorded 91.66 per cent
mortality. Nematicidal effect was noticed in M. incognita and R. reniformis. In
M. incognita hatching was reduced by 66.6 per cent for chitosan 5% and chitosan
7%, followed by chitin 7% (53.34 per cent). The juveniles (J2) were highly
susceptible to all the formulations at 7% causing 100 per cent mortality on second
day. Chitin 7% caused 78.54 per cent mortality in R. reniformis on third day.
Pot culture studies revealed that, in brinjal, H. vigintioctopunctata
population was lowered in plants treated with chitosan gel 7% and chitosan 7%,
the population being 2.86 and 4.83 at seven days after treatment (DAT), while in
control it was 9.09 per plant. Incidence of M. viridanus and Aphis gossypii
Glover was also less in plants treated with chitosan 7% and chitosan gel 7%. The
plant height, number of leaves and branches and were also more in the treatment,
chitosan gel 7%. Highest yield was recorded in chitosan 7% (149.69 g plant-1
harvest-1). In cowpea, A. craccivora population was significantly reduced
(32.97) in plants treated with chitin 7% while in control it was 197.98 at seven
DAT. Plants treated with chitin 7%, chitosan gel 7% and Biorakshak 2% showed
less damage of mite, Tetranychus sp. Chitin 7% was the best treatment that
favored the growth parameters in cowpea. In tomato, M. incognita population in
soil was least in plants treated with chitin 7% and chitosan 7% (36 and 52.13)
where as in root samples it was least (278.66) in chitin 7% treated plants.
Incidence of Liriomyza trifoli Burgess and cercospora leaf spot was also less
in these treatments.
Field experiment on cowpea revealed that, chitin 7% took seven days to
reduce the population of A. craccivora (164.82 plant-1), followed by chitosan 7%
and chitosan gel 7% (189.62 and 214.4 respectively), while in plots treated with
dimethoate 30EC @ 0.2% there was complete control. Yield plot-1 was 1.76 kg in
chitin 7% and it was 1.8 kg in dimethoate 30EC @ 0.2%. In the field trial on
tomato, population of nematodes in soil and root sample were less in plots treated
with chitin 7% (152.5, 38.75) than in control plots (532.75, 123.75), while in
chemical treatment with cartap hydrochloride 4G @ 1 kg a.i.ha-1 it was 72.25 and
5.5 respectively. The incidence of L. trifoli was less in chitin 7% treated plants
and that of leaf curl virus was less in treated plants when compared to control.
Significantly high yield was noted with crude chitin 7g kg-1 (2.39 kg plot-1)
compared to control (1.10 kg plot-1).
The study indicated that the potential of natural biopolymers chitin and
chitosan can be exploited for the holistic management of crop plants as it has
capacity to regulate the population of insect and nematode pests as well as plant
diseases. The growth and yield promoting attributes and safety to natural enemies
makes them ideal candidates in integrated pests and disease management as well
as integrated nematode management programmes.