EFFECT OF NEEM OIL ON CERTAIN LEPIDOPTEROUS PESTS OF BLACKGRAM (Vigna munqo ( L.) Hepper)
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Date
1988
Authors
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY, RAJENDRANAGAR, HYDERABAD
Abstract
Experiments were conducted during 1987-88 in the
department of Entomology and at the Agricultural College
farm, Bapatla to know the effect of neem oil on certain
lepidopterous pests of blackgram.
Under laboratory conditions among the concentrations of
neem oil (0·5 to 16.0%) tested, 8.0 and 16.0 per cent
e xh ib ited cent per cent repellency and antifeedant property
against both s. littu-·a and!:.!._ r·icini· The ov i position of
b oth the insects was deterred as the concentration of neem
oil i n creased ( 0.5 to 16-0% ) but, complete deterrency was
ob serv ed at 16 per cent neem oil· The growth a n d development
in r espect of adult eme r gence, g r owth index, length of larva,
weight of larva and p upa decreased while the develo p menta l
period increased as the concentration of neem oi l i n c l-·ease d
f r om o . 5 to 4 -0%. Bu t at 8 a n d 16 per cent t he g r owt h a nd
d evelopment of bot h t h e insects was complete l y supp r essed .
. '
The hatchability of both s. litura and P . ricini eggs was
inversly proportiona l to neem oil's concentration. Neem oil
at 0.5 and 1.0 % lost its antifeedant property by 5th day and
by the 6th day of treatment at 2-0% when exposed to sunlight.
Neem oil at 8 and 16 per cent exhibited phytotoxic symptoms
but the percentage of leaf area affected was more on castor
leaves than on blackgram.
Both endosulfan 0.07% and monocrotophos 0.04% were
superior over neem oil in causing larval mo1··tal i ty of
s. 1 it til·· a and H. a1··mi ger·a. Insecticides exhibited
synergistic effect, when used along with neem oil·
Under field cond itions also, endosulfan 0.07% + neem o il
1-0% recorded highest per cent reduction ( 76 -6,77-5 and
70-1%) of pod bo r er complex of blackgram (S . litur·a, H.
armigera and M· testulalis) with correspon di ng i n crease i n
yield (369-44 Kg/ha) compared to neem oil and i n secticides
when used alone. But based on economics of treatments ,
endosulfan 0.07% recorded maximum net profit of Rs . 508.12/ha
with net incremental cost benefit ratio of 1 Neem
'- . oil 0.5 and 1.0 per cent (1 : 0-79 and 1
superior over neem oil 1-0% + endosulfan 0 -07% (1 (> . 50)
and neem oil 1·0% + monocrotophos 0-04% (1 : 0 - 49) .
All the treatments applied twice at 15 day interval
r ecorded maximum net profits with highest cost benefit ratios
than the treatments applied thrice at 10 day interval
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Keywords
EFFECT, NEEM OIL, CERTAIN, LEPIDOPTEROUS, PESTS,BLACKGRAM,