MSc

The study entitled " Management of sucking pest complex in chilli using botanical and microbial pesticides " was conducted during 2016-2018, in the
Department of Agricultural Entomology, College of Agriculture, Vellayani with
an objective to manage the sucking pest complex of thrips (Scirtothrips dorsalis
Hood), aphids (Aphis gossypii Glover) and mites (Polyphagotarsonemus latus
Banks) in chilli using botanical and microbial pesticides.
Laboratory evaluation of the botanical and microbial agents was done
taking aphid (A. gossypii) as test insect. Cashew nut shell liquid (CNSL), a
potential insecticide and a cheap by-product of cashew industry containing a
mixture of phenolic compounds was evaluated as emulsions at different
concentrations (0.025, 0.05, 0.075, 0.1 and 0.2 %) along with Neem Seed Kernel
Extract (NSKE) emulsion 5 %, neem oil emulsion 2 % and commercial botanical
pesticide oxuron 5 mL L-1. Thiamethoxam 0.015 % served as chemical check.
CNSL 0.2 % and neem oil 2 % caused significantly high mortality of 64
and 58 per cent respectively at 24 hours after treatment (HAT) and was on par
with chemical check thiamethoxam 0.015 %. At 48 HAT, CNSL 0.075, 0.1 and
0.2 % with per cent mortality 88.67, 86 and 92.67, respectively was found to be as
effective as oxuron 5 mL L-1 and thiamethoxam 0.015 % and significantly
superior over other treatments. At 72 HAT, thiamethoxam 0.015 %, oxuron 5 mL
L-1, CNSL 0.2 % and CNSL 0.1 % showed 100 per cent mortality which did not
vary significantly from the other treatments viz., CNSL 0.075 %, CNSL 0.05 %,
CNSL 0.025 %, neem oil 2 % and NSKE 5 % with 99.33, 98.67, 98, 98 and 97.33
per cent mortality respectively. Based on the results of the laboratory evaluation,
CNSL 0.2 % which was found superior at different intervals and CNSL 0.075 %
the lowest effective concentration were selected for further evaluation.
All the microbial agents evaluated viz., Beauveria bassiana, Metarhizium
anisopliae, Lecanicillium lecanii and Lecanicillium saksenae were found to infect
A. gossypii, among which L. lecanii and L. saksenae @ 107 spores mL-1 were
significantly superior. L. lecanii @ 107 spores mL-1 caused in 54.5, 87.5, 100 per
cent and L. saksenae @ 107 spores mL-1 55, 85.5 and 100 per cent mortality of
aphids at 24, 48 and 72 HAT respectively.
CNSL was found to be compatible with all microbial agents tested as per
Hassan‟s classification scheme showing 60-65 per cent growth inhibition in disc
diffusion assay in Potato dextrose agar plates.
A pot culture experiment was carried out in chilli variety Jwalamukhi with
effective botanical pesticides (CNSL 0.075 %, CNSL 0.2 %, neem oil 2 %,
oxuron
5 mL L-1) selected based on laboratory evaluation along with L. lecanii
@ 107 spores mL-1 and a combination treatment (CNSL 0.2 % + L. lecanii @ 107
spores mL-1) to assess the field efficiency against sucking pest complex.
Thiamethoxam 0.015 % served as chemical check. Two rounds of application one
each at vegetative (30 days after planting) and reproductive phase (60 days after
planting) of the crop were administered.
In the vegetative stage, 99.96, 88.87, 98.66, 88.94 per cent reduction in
thrips population over control was observed in treatments with CNSL 0.2 % +
L. lecanii @ 107 spores mL-1, L. lecanii @ 107 spores mL-1, CNSL 0.075 % and
CNSL 0.2 % respectively at 3 DAT. The mite population was found to be least in
the treatments CNSL 0.2 % (0.32 mites leaf-1 at
5 DAT) and CNSL 0.075 %
(0.53 and 0.35 mites leaf-1 on 3 and 5 DAT) which did not vary significantly with
the combination of CNSL 0.2 % + L. lecanii @ 107 spores mL-1 with 0.42 and
0.29 mites leaf-1 on 3 and 5 DAT respectively. The population of mites was
significantly lower (0.15 leaf-1) in chemical check than all other treatments at
seven days after treatment followed by CNSL 0.2% and L. lecanii @ 107 spores
mL-1 recording mite population of 0.34 and 0.43 leaf-1 respectively.
CNSL 0.2 %, L. lecanii @ 107 spores mL-1 and the combination treatment
were found to be superior in managing chilli thrips and as effective as chemical
check thiamethoxam 0.015 % in the reproductive phase. These treatments
recorded low population (1.27, 1.23 and 1.23 thrips leaf-1 respectively) at 14 DAT
as against 4.5 thrips leaf-1 in control. The mites were controlled effectively by
both CNSL 0.2 % and CNSL 0.075 % upto 3 DAT. The botanical CNSL 0.2 %
gave control upto 7 DAT with 1.07 mites leaf-1 as against 3.1 mites leaf-1 in
control. Neem oil 2 % and oxuron 5 mL L-1 were found to be the next effective
treatments against chilli mites.
Reduced leaf curl, on par with chemical check was observed in treatments
CNSL 0.075 %, CNSL 0.2%, combination of CNSL 0.2 % + L. lecanii @ 107
spores mL-1 and neem oil 2 % as evidenced by lesser value of leaf curl index, an
indicator of damage by sucking pest complex (1, 1.33, 1.33 and 1.33
respectively), at 70 days after planting. The corresponding index in the control
during the same period was 3.0. L. lecanii @ 107 spores mL-1 was also found to
reduce the leaf curl index (1.67) though inferior to the above treatments.
CNSL at the higher concentration of 0.2 % though found effective in
managing the population of thrips and mites, did not show improved plant growth
characters indicating possible growth retarding effect as evidenced by inferior
growth attributes in comparison with chemical check. Significantly low plant
height (23.2 cm), number of leaves (45.33), shoot fresh weight (13.25 g plant-1)
and shoot dry weight (1.05 g plant-1) were observed in comparison to chemical
check. L. lecanii @ 107 spores mL-1 and CNSL 0.075 % treated plants showed
better growth characters than those treated with CNSL 0.2 %.
The results of the study indicated the suitability of CNSL 0.2 %, CNSL
0.075 % and the combination treatment of CNSL 0.2 % + L. lecanii @ 107 spores
mL-1 in sucking pest complex management. Thus considering the effectiveness in
managing the sucking pests and their effect on plant growth attributes, CNSL
0.075 % and L. lecanii @ 107 spores mL-1 are better choices for eco-friendly
management of sucking pest complex of chilli.