Efficacy of entomopathogenic nematodes against potato tuber moth, Phthorimaea operculella (Lepidoptera: Gelechiidae) under laboratory conditions

Biocontrol Science and Technology (Impact Factor: 0.94). 01/2013; 23(2):146.


The susceptibility of potato tuber moth, Phthorimaea operculella (Zeller)
(Lepidoptera: Gelechiidae) to native and commercial strains of entomopathogenic
nematodes (EPNs) was studied under laboratory conditions. Native strains
of EPNs were collected from northeastern Iran and characterised as Steinernema
feltiae and Heterorhabditis bacteriophora (FUM 7) using classic methods as well
as analysis of internal transcribed spacer (ITS) and D2/D3 sequences of 28S
genes. Plate assays were performed to evaluate the efficiency of five EPN strains
belonging to four species including Steinernema carpocapsae (commercial strain),
S. feltiae, Steinernem glaseri and H. bacteriophora (FUM 7 and commercial
strains). This initial assessment with 0, 75, 150, 250, 375 and 500 IJs/ml
concentrations showed that S. carpocapsae and H. bacteriophora caused the
highest mortality in both larval and prepupal stages of P. operculella, PTM.
Thereafter, these three strains (i.e. S. carpocapsae, H. bacteriophora FUM 7 and
the commercial strains) were selected for complementary assays to determine the
effects of soil type (loamy, loamy�sandy and sandy) on the virulence of EPNs
against the second (L2) and fourth instar (L4) larvae as well as prepupa. A soil
column assay was conducted using 500 and 2000 IJs in 2-ml distilled water.
Mortality in the L2 larvae was not affected by the EPN strain or soil type, while
there was a significant interactive effect of nematode strains and soil type on
larval mortality. The results also showed that EPN strains have higher efficiency
in lighter soils and caused higher mortality on early larvae than that in loamy soil.
In L4 larvae, mortality of PTM was significantly influenced by nematode strain
and applied concentrations of infective juveniles. The larval mortality induced by
S. carpocapsae was higher than those caused either by a commercial or the FUM
7 strain of H. bacteriophora. Prepupa were the most susceptible stage.

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Available from: Mahnaz Hassani kakhki, Oct 21, 2015
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