Bioefficacy of Entomopathogenic Nematodes (EPNs) Steinernema carpocapsae (Weis.) and Heterorhabditis indica (Poinar) against Spodoptera litura (Fab.)
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Date
2006
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY, RAJENDRANAGAR, HYDERABAD
Abstract
The present investigation entitled ‘Bioefficacy of entomopathogenic
nematodes (EPNs) Steinernema carpocapsae (Weis.) and Heterorhabditis
indica (Poinar) against Spodoptera litura (Fab.)’ was undertaken in the
Department of Entomology, Agricultural College, Bapatla during 2005-06. The
bioefficacy studies were carried out against third instar larvae and three day
old pupae of S. litura in soil column assay using sand, red and black soils.
The role of antidesiccants in extending the pathogenicity of the test EPNs was
also evaluated.
The median lethal concentrations (LC50s) of H. indica (10.8, 13.8, 23.8
and 15.7 IJs / larva) were lower than those of S. carpocapsae (13.8, 15.9,
28.8 and 19.4 IJs / larva) in sand, red and black soils at 10% moisture and
also at 15% moisture in black soil, respectively after 48 h of post infection in
third instar larvae of S. litura.
The pathogenicity of H. indica was quicker with lower median lethal
times (LT50s) (55.9-31.8, 66.3-33.1, 80.7-31.6 and 81.0-31.1 h) compared to
S. carpocapsae (64.2-33.2, 69.3-35.5, 83.5-32.8 and 86.6-35.4 h) in the
dosage range of 5-30 IJs / larva in sand and red soils, 10-50 IJs / larva in
black soil at 10% moisture and 5-35 IJs / larva in black soil at 15% moisture,
respectively.
H. indica resulted in higher per cent cumulative larval mortalities of
S. litura (78.3-100.0 at 72 h, 36.7-100.0 at 60 h, 40.0-96.7 at 96 h and 60.0-
100.0 at 96 h) compared to those of S. carpocapsae (65.0-100.0 at 72 h,
23.4-100.0 at 60 h, 36.7-91.7 at 96 h and 55.0-100.0 at 96 h) in sand, red and
black soils at 10% moisture and black soil at 15% moisture, respectively with
the dosage range of 5-30 IJs / larva.
Feeding inhibition in H. indica infected larvae (51.0-90.3, 40.2-85.5,
14.2-55.3 and 31.0-71.9%) was more than that of S. carpocapsae (41.8-88.4,
35.2-79.6, 8.8-48.7 and 22.2-62.6%) at the dosage range of 5-30 IJs / larva in
the corresponding test soils. Similarly, the per cent reduction in weight gain of
the infected larvae was higher with H. indica (61.2-92.7, 47.0-91.1, 21.8-66.2
and 35.1-82.3) compared to that of S. carpocapsae (53.4-91.0, 42.7-85.6,
17.5-56.2 and 26.5-65.6) in the respective soils and dosages.
There is significant increase in larval mortality, feeding inhibition and
weight reduction of the infected larvae with increase in dosages of the test
EPNs and interval of observation i.e., 24-72 h in sand and red soil or upto 96
h in black soil.
Even against pupae, H. indica was more pathogenic with its lower
LC50s (78.3, 83.2, 113.1 and 91.6 IJs / pupa) compared to those of
S. carpocapsae (99.7, 103.7, 130.8 and 103.0 IJs / pupa) in sand, red and
black soils at 10% moisture and at 15% moisture in black soil, respectively
after 96 h of post infection.
The LT50s of H. indica against pupae were also lower (85.3-43.7, 86.2-
45.7, 139.2-61.7 and 107.4-50.2 h) compared to those of S. carpocapsae
(102.9-48.4, 108.6-53.6, 144.9-68.0 and 125.2-51.5 h) in the respective test
soils at the dosages of 90-180 IJs / pupa.
The per cent reduction in adult emergence from the infected pupae
increased with increase in dosage (30-180 IJs / pupa) of S. carpocapsae
(44.8-93.0, 32.2-92.8, 14.1-78.3 and 28.5-90.0) and H. indica (51.9-96.7,
39.3-92.6, 28.5-89.6 and 35.5-92.6) in the mentioned test soils, but without
any significant difference between the two EPNs.
The per cent increase in larval mortality of third instar larvae of S. litura
over untreated check due to the use of antidesiccants was higher with glycerin
(11.2-64.3 and 15.6-75.3), followed by liquid paraffin (5.6-63.7 and 13.3-70.9)
and Triton X 100 (5.6-52.5 and 8.3-63.8) at 24-48 h of incubation prior to
larval treatment with S. carpocapsae and H. indica, respectively in all the test
soils.
The pathogenic effects of the test EPNs were better in sandy soil
followed by red soil both at 10% moisture, black soil at 15% moisture and at
10% moisture.
Description
Keywords
Bioefficacy, Entomopathogenic, Nematodes, Steinernema, carpocapsae, Heterorhabditis, indica, against, Spodoptera, litura