STUDIES ON BIOLOGY AND SAFETY OF INSECTICIDES TO GREEN LACEWING, Chrysoperla carnea Stephens (NEUROPTERA: CHRYSOPIDAE)
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Date
2016
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PROFESSOR JAYASHANKAR TELANGANA STATE AGRICULTURAL UNIVERSITY. HYDERABAD
Abstract
The present study entitled “ Studies on biology and safety of insecticides to
Green lacewing, Chrysoperla carnea Stephens (Neuroptera: Chrysopidae) ” was
conducted at AICRP on Biological Control of Crop Pests, College of Agriculture,
Rajendranagar, Hyderabad, during 2015-16.
During the period of study, biology of C. carnea on two laboratory hosts, Corcyra
cephalonica and Spodoptera litura as well as on natural host, Aphis craccivora were
documented under laboratory conditions. Maximum pre oviposition period of 6.8 ± 0.37
days and oviposition period of 30.0 ± 0.32 days was observed when larvae of C. carnea
were fed on eggs of S. litura and minimum of 5.6 ± 0.24 and 23.6 ± 1.03 days respectively
were observed on A. craccivora nymphs compared to eggs of C. cephalonica (6.2 ± 0.37
and 27.4 ± 0.51 days). Maximum fecundity of 569.4 ± 8.88 eggs per female was recorded
on C. cephalonica followed by S. litura ( 359.6 ±5.57) and A. craccivora (299.0 ± 5.50).
Highest egg hatchability (88.0 ± 2.0), per cent larval pupation (86.0 ± 2.45) and adult
emergence (76.0 ± 4.00) was observed when larvae were fed with C. cephalonica eggs
whereas lowest on S. litura (74.0 ± 2.45, 70.0 ± 3.16 and 62.0 ± 2.0 per cent).
The total larval duration on three different hosts ranged from 7-10 days, minimum
being on C. cephalonica (7.2 ± 0.2 days) and maximum on S. litura (9.8 ± 0.2 days)
whereas total larval duration of 9.0 ± 0.0 days was recorded when fed on A. craccivora
nymphs. Highest adult longevity of 41.6 ± 0.51(female) and 34.6 ± 0.25 (male) days was
seen in S. litura and shortest female longevity of 39.6 ± 0.51 and male longevity of 29.0 ±
0.45 days on C. cephalonica. Sex ratio was slightly female biased on all three host where
females survived longer than males.
Results revealed that maximum oviposition period of 36.6 days, highest fecundity
with 749.8 eggs per female and maximum of 87.0 per cent egg hatchability as well as
highest adult longevity of 28.0 days for males and 41.8 days for females were observed
when adults were fed with combination artificial feed (proteinex and glucose) + 20g floral
feed (castor pollen) compared to all the biological parameters of C. carnea when fed with
artificial feed alone.
Studies on prey preference of C. carnea among four different aphid species
exhibited an order of preference i.e., Aphis craccivora > Aphis gossypii > Rhopalosiphum
maidis > Lipaphis erysimi. The results clearly indicated that C. carnea could be a better
biological control agent against A. craccivora which is a major pest of Groundnut.
Bioassay studies on safety of six insecticides viz., Chlorantraniliprole, Spinosad,
Emamectin benzoate, Imidacloprid, Thiamethoxam and Diafenthiuron at recommended
dose tested against egg hatchability, larval mortality, pupation, adult emergence and
mortality of C. carnea revealed that among the insecticides, Imidacloprid was found less
toxic recording maximum egg hatching of 86.67 per cent and least egg hatchability of
51.67 per cent was observed in Thiamethoxam. After 12 hours, none of the treatments
caused mortality to larvae of C. carnea when fed with both insecticide sprayed Corcyra
eggs and larvae. After 24 and 48 hours of treatment Chlorantraniliprole has recorded
highest mortality both on treated eggs (26.67 and 46.67 %) and larvae (26.67 and 63.33 %)
showing its toxic effects. Whereas lowest mortality (3.33 and 6.67 %) was exhibited by
Spinosad after 24 hours in both the conditions. But, after 48 hours, Imidacloprid registered
least mortality of 13.33 and 26.67 per cent to C. carnea larvae when fed on treated eggs
and larvae of C. cephalonica respectively.
In case of adult mortality, Thiamethoxam registered complete mortality and
Diafenthiuron caused least mortality of 3.33 per cent after 48 hours of treatment From the
study it can be concluded that Diafenthiuron and Imidacloprid are said to be least toxic to
C. carnea at all stages with maximum pupation and adult emergence