PhD

ABSTRACT
The present investigation entitled “Cashew Nut Shell Liquid (CNSL) based
botanical insecticide for pest management in yard long bean (Vigna unguiculata
subsp. sesquipedalis (L.) Verdc.)” was conducted at Department of Agricultural
Entomology, College of Agriculture, Vellayani and Farming Systems Research
Station, Sadanandapuram during 2016 to 2019 with an objective to evaluate the
insecticidal property of CNSL against pests of cowpea and to develop a CNSL based
botanical pesticide.
Various concentrations of CNSL emulsions (0.05 to 0.2 %) derived from two
different processing methods viz., drum roasting (DR) and steam boiling (SB) were
screened against the test insects Aphis craccivora Koch., Riptortus pedestris
Fabricius. and Spodoptera litura Fabricius. Cent per cent mortality of A. craccivora
was observed in 0.1 % of CNSL-SB and 0.1 and 0.2 % of both CNSL-SB and DR at
48 hours after treatment (HAT) an effect comparable to chemical check,
thiamethoxam 25 WG 0.03 %. LC50 values of CNSL DR and SB against A
craccivora were computed to be 0.079 and 0.084 respectively with corresponding
LC90 values of 0.25 and 0.275. The bioassay of CNSL against R. pedestris indicated
that at 48 HAT, 0.2 % of both CNSL-DR and SB and 0.1 % CNSL-SB produced
significantly higher mortality even though inferior to chemical check. But at 72 HAT,
the mortality obtained in 0.1 and 0.2 % CNSL-DR and CNSL-SB (96.67 to 100 per
cent) was comparable with that of chemical check thiamethoxam. The LC 50 values
obtained for R. pedestris at 48 HAT were 0.095 and 0.102 per cent respectively for
CNSL-DR and CNSL-SB with corresponding LC 90 values of 0.275 and 0.334 per
cent. The effect of CNSL on chewing insect S. litura was slow, in which a mortality
of 40.00 and 43.33 per cent were observed at 7 days after treatment (DAT) for 0.2 %
of CNSL-DR and CNSL-SB respectively. The LC50 values of CNSL DR and SB for
S. litura was 0.362 and 0.373 respectively and corresponding LC90 values were 2.797
and 3.105.
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Two emulsifiable concentrate (EC) formulations of CNSL viz., CNSL 20 %
EC (EC-1) and a combination product of CNSL and pongamia oil in the ratio 20:20
(EC-2) were developed with isopropyl alcohol as solvent and sodium oleate and span
20 (91:9) as emulsifier blends based on the HLB value of CNSL (computed as 17.12)
and emulsion characteristics (blooming rating, emulsion stability and temperature
stability). The composition of the EC-1 formulation was CNSL (ai) : solvent :
emulsifier : water : co solvent in the ratio 20:53:12:10:5 and EC-2 was CNSL+
pongamia oil (ai) : solvent : emulsifier : water : co solvent in the ratio (20+20) : 33 :
12 : 10 : 5. The physiochemical characterization of the formulation showed a pH of
7.99 and 8.1and electrical conductivity of 1.709 and 1.515 dS m-1 for EC-1 and EC-2
respectively. The formulations were stored at controlled temperatures to evaluate
their stability over time. Both formulations complied the BIS standards for stability
and physicochemical properties. The bioassay evaluation of the formulation against
the test insects revealed that CNSL @ 0.3 % concentration prepared out of EC-1 and
EC-2 were as effective as chemical check thiamethoxam 25 WG (0.03%) against A.
craccivora with 93.75 and 97.92 % mortality respectively at 48 HAT. When tested
against pod bug; R. pedestris, EC-1 and EC-2 @ 0.3 % caused mortality of 77.78 and
81.48 per cent respectively at 48 HAT and CNSL EC @ 0.1 % produced around 77
per cent mortality. When tested against S. litura EC-1 and EC-2 produced superior
mortality of 66.67 and 74.07 % respectively compared to other treatments at 7 DAT,
though inferior to thiamethoxam 25 WG (0.03%). The shelf life studies conducted at
1, 3 and 6 MAP did not show deterioration of formulation with respect to stability
and bioefficacy.
High Performance Liquid Chromatography analysis revealed the presence of
19.27 % cardol and 0.734 % cardanol in technical CNSL, which are considered to be
the main constituents having insecticidal property. The bioassay evaluation showed
100.00 and 82.78 % mortality of A. craccivora at 48 HAT for cardol (513ppm) and
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cardanol (24 ppm) respectively. The mortality of S. litura treated with the same was
89.56 and 78.89 % respectively at 7 DAT.
The effect of CNSL on the crop indicated its safety with no phytotoxicity
symptoms on cowpea at effective (0.3 %) and above effective doses (0.6%) as per
phytotoxicity rating scale of CIBRC. No significant adverse effect was observed
against natural enemies Coccinella transversalis Fabricius. and Bracon sp and
pollinators Apis cerana indica Fabricius. and Tetragonula travancorica Shanas and
Faseeh. for CNSL formulations when evaluated in the laboratory by dry film
technique.
An invitro study was carried out to study the effect of CNSL on microbial
biocontrol agents like Pseudomonas fluorescence and Beauveria bassiana. No
inhibition was noticed on growth of P. fluorescence when exposed to CNSL in
culture plates by well diffusion technique. The per cent growth inhibition of B.
bassiana exposed to CNSL fell in the score one categorized as harmless. CNSL is
found to be compatible with biocontrol agents, B. bassiana and P. fluorescence.
A field experiment was carried out to evaluate the efficacy of the CNSL
formulations developed, for the management of pests of cowpea. The treatments
consisted of 0.1 and 0.3 % concentrations of the CNSL prepared from formulations
developed (EC-1 and EC-2), botanical pesticides neem oil garlic emulsion (NOG) 2%
and Neemazal 2% and combinations of half doses of CNSL + half dose of NOG.
Thiamethoxam 25 WG 0.03 % and dimethoate 30 EC 0.05% served as chemical
checks. All the treatments containing CNSL formulations significantly reduced the
population of sucking pests over control in the vegetative phase of the crop. Lower
populations of aphid; A. craccivora, mite; Tetranychus sp and hopper; E. kerri were
registered in plots treated with 0.3 % CNSL EC-1, EC-2 and combination of NOG
1% + 0.15 % CNSL EC-1. A population of 0.56, 1.22 and 1.44 aphids leaf-1, 1.00,
1.22 and 2.11 mite leaf-1 and 0.44, 0.33 and 1.00 hopper leaf-1 were noticed in treated
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plants at 7 days after spraying (DAS) as against 20.67 aphids leaf-1, 19.33 mites leaf-1
and 10.22 hoppers leaf-1 in untreated control. At 7 DAT, CNSL @ 0.3 % of both EC-
1 and EC-2 could manage sucking insect pest populations as effectively as
thiamethoxam 25 WG 0.03% and was significantly superior to botanical pesticides
NOG 2% and Neemazal 1%. The same trend was noticed in the reproductive phase
of the crop as well. Treatments with 0.3 % CNSL of EC-1and EC-2 registered
significantly superior effect over other treatments against pod bug, R. pedestris (0.83
and 1.17 plant -1 at 5 DAT) which was on par with thiamethoxam 25 WG 0.03% as
against 9.17 plant -1 in untreated control. The CNSL formulations were not as
effective as chemical check dimethoate 30 EC 0.05% in managing chewing pests.
However significantly lower population of 3.67 larvae plant-1 was observed in plants
treated with 0.3 % CNSL of both EC-1 and EC-2 and were superior to botanical
pesticides NOG 2 % (7.67 plant -1) and Neemazal 1% (8.33 plant -1) The treatments
containing CNSL were found to be safe to natural enemies and pollinators as
evidenced by no variation in their population from that of the untreated control.
Biometric parameters (height, internodal length and number of leaves) did not
exhibit any adverse effect on plant growth up on treatment with CNSL. Highest yield
was recorded in plants treated with thiamethoxam 25 WG 0.03% (7.78 t/ha) which
was on par with that of treatments with 0.3 % CNSL of both EC-1 and EC-2 (7.25
and 7.34 t/ha) and the treatment with combination of NOG 1% + 0.15% CNSL of
EC-2 (7.25 t/ha).
The insecticidal efficacy of CNSL emulsion against A. craccivora, R.
pedestris and S. litura were proved. EC formulations was prepared from crude CNSL
using isopropyl alcohol as solvent and emulsifier blend of sodium oleate and span 20.
Two different formulations viz., 20 % CNSL EC (EC-1) and combination product of
CNSL 20 % and pongamia oil 20 % (EC-2) were developed in the present study.
CNSL @ 0.3 % of both EC-1 and EC-2 were found to be as effective as chemical
pesticides in managing sucking pests of cowpea. The developed formulations were
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stable and have shelf life up to 6 months after preparation. Both the laboratory assay
and field evaluation with CNSL formulation showed promising result against
different pests of cowpea especially sucking pests like aphid, mite, thrip, hopper and
pod bug and was comparatively safe to natural enemies and pollinators.