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STUDIES ON ENTOMOPATHOGENIC NEMATODE, STEINERNEMA SPP. ON MAJOR LEPIDOPETARAN PESTS OF CABBAGE

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Title STUDIES ON ENTOMOPATHOGENIC NEMATODE, STEINERNEMA SPP. ON MAJOR LEPIDOPETARAN PESTS OF CABBAGE
 
Creator SREERAMAIAH, V.N
 
Contributor UMA MAHESWARI, T
 
Subject ENTOMOPATHOGENIC, NEMATODE, STEINERNEMA, LEPIDOPETARAN, PESTS, CABBAGE
 
Description Studies related to infectivity/pathogenicity of entomopathogenic
nematode, Steinernema asiaticum, against major lepidopteran insect
pests of cabbage, its survival and mass multiplication, effect of
temperature, U.V radiation and storage period on survival and
pathogenicity of S. asiaticum on host insects were carried out in the
laboratory, Department of Entomology, College of Agriculture,
Rajendranagar, Hyderabad from October 2007 to July 2008.
Studies made on pathogenicity of S. asiaticum against two
lepidopteran pests of cabbage i.e. Plutella xylostella and Spodoptera
litura and the laboratory check, Corcyra cephalonica revealed that, P.
xylostella was more susceptible to S. asiaticum recording maximum
mortality of 67 per cent within 72 hrs of inoculation at a dose of 180
IJs per larva followed by C. cephalonica showing 61 per cent mortality
within 120 hrs of inoculation at 210 IJs per larva. Spodoptera litura
recorded a maximum mortality of 58 per cent. It was clear that with
increasing level of inoculation, there was a gradual increase in the
larval mortality. With regard to the median lethal dose (LD50), low for
P. xylostella it was compared to C. cephalonica and S. litura. LD50 value
of 70.02 IJs for P. xylostella, 71.65 IJs for C. cephalonica and 92.66 IJs for S. litura were recorded within 72 hrs, for P. xylostella and 120
hrs for C. cephalonica and S. litura. The lethal time (LT50) recorded was
65.49 hrs (2.7days) for P. xylostella, followed by 114.21 hrs (4.7 days)
for C. cephalonica and 117.09 hrs (4.8 days) for S. litura at an
inoculum level of 60 IJs for P. xylostella and 120 IJs for S. litura and
C. cephalonica.
With regard to mass multiplication of S. asiaticum on three
hosts i.e. P. xylostella, S. litura and C. cephalonica, the results revealed
that C. cephalonica was found to be the suitable host recording a
maximum recovery of 1,24,600 IJs when inoculated with 90 IJs per
larva followed by S. litura recording 45,200 juveniles at 60 IJs.
However, P. xylostella was the least suitable host for mass
multiplication as only 6,060 juveniles could be recovered when 90 IJs
were inoculated per larva.
Studies on the effect of temperature on survival of the
nematode, S. asiaticum made under laboratory conditions revealed
that temperature ranging from 5 to 20 oC is said to be optimum for
getting juveniles with a maximum survival percentage ranging from 94
to 100. However, it was clear from the experiment that more than 90
per cent of juveniles of S. asiaticum could survive at a temperature of
20 oC. When the temperature was beyond 20 oC, the rate of survival of
juveniles reduced. While testing the effect of temperature on infectivity
of S. asiaticum against three insect hosts, temperature of 30 oC was
recorded as optimum temperature which resulted in 78.4, 48.8 and
58.4 percent mortality of the larvae of P. xylostella, S. litura and C.
cephalonica, respectively. Temperature of 5 oC was proved to be most
unfavourable for causing infection of larva of P. xylostella, S. litura and
C. cephalonica by S. asiaticum which has resulted in the lowest
mortality of the larvae i.e. 34.4, 12.8 and 18.4 per cent, respectively.
Attempts made to investigate the impact of U.V radiation on
survival of juveniles of S. asiaticum revealed that time of exposure of
IJs to U.V radiation had significant effect on the survival of juveniles
which further influenced their infectivity expressed in terms of
mortality of the host insect. But as the time of exposure increased, the
survival of juveniles decreased. When IJs were exposed to a minimum
period of 30 minutes to U.V radiation, it has resulted in 89.8 per cent
survival of the IJs. Where as 60 minutes exposure resulted 78.8 per
cent and 90 minutes with 64.6 per cent survival. At maximum period
of exposure i.e. 150 minutes, there was only 34 per cent survival.
However, present studies revealed that a threshold time limit of 120
minutes exposure of IJs to U.V. light could definitely result in a
survival of 51.8 per cent of the exposed juveniles of S. asiaticum. More
than 120 minutes of exposure i.e. two hours could result in reduction
in survival of infective juveniles of S. asiaticum. Where as
pathogenicity against three pests revealed that maximum of 15
minutes exposure of IJs of S. asiaticum could cause 72.8, 53 and 54 per cent mortality of the P. xylostella, S. litura and C. cephalonica as
compared to maximum of 75.2, 58 and 59 per cent by the infective
juveniles from control, respectively. Maximum larval mortality of 33.6,
20 and 24 per cent was recorded when juveniles were exposed to UV
radiation for 180 minutes against P. xylostella, S. litura and C.
cephalonica, respectively.
Ageing of IJs on infectivity was elucidated against three hosts
revealed that the juveniles of S. asiaticum stored for 15 days when
inoculated to the third instar larvae of P. xylostella, S. litura and C.
cephalonica resulted in causing maximum mortality of 68.8, 50 and
58 per cent as compared to control mortality of 77.6, 61 and 65 per
cent, respectively. Maximum mortality of only 22.4, 6 and 8 per cent
was recorded against P. xylostella, S. litura and C. cephalonica,
respectively when the larva were inoculated with IJs that were stored
for a long period of 75 days. Storage period, adversely affect the
infectivity of the S. asiaticum on host insect.
 
Date 2016-07-30T14:30:33Z
2016-07-30T14:30:33Z
2008
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/70317
 
Language en
 
Relation D8335;
 
Format application/pdf
 
Publisher ACHARYA N. G. RANGA AGRICULTURAL UNIVERSITY, RAJENDRANAGAR, HYDERABAD