strategies, such as biocontrol agents, for use in PTM control must rely on behavior of
its larvae which move in the soil, for pupation or infesting tubers. With regard to the
ability of EPNs that can actively search their hosts in a complex environment such as
soil, Hassani-Kakhki et al. (2013) assessed the effect of EPNs isolate/species on
PTM. The primary objective of their work was to evaluate the susceptibility of
different PTM stages, i.e. second (L2) and fourth instar larvae (L4) as well prepupa
to four EPN species with different foraging strategies, S. carpocapsae, [isolated IJs
from commercial product under the trade name Capsanem®], S. feltiae, S. glaseri
and H. bacteriophora FUM7 and commercial isolate [under the trade name
Larvanem®] in Petri dishes. The initial assessment on filter paper showed that
S. carpocapsae and H. bacteriophora (FUM7 and commercial) species caused the
highest mortality on both larval and prepupal stages of PTM. In general, prepupa
was the most susceptible stage while pupa had the lowest mortality.
A possible approach for control the destructive stages of PTM that infest tuber or
inter to the soil for pupation could be the application of EPNs on the soil surface.
Hence, complementary tests in soil columns, by three soil types: loamy, sandy and
sandy-loamy, containing infested tuber were established using S. carpocapsae and
H. bacteriophora (FUM7 and commercial) species. Results from this semi-field
assay indicated larval mortality induced by S. carpocapsae (88%) was higher than
those caused either by the commercial population of H. bacteriophora (79%) or by
H. bacteriophora FUM 7 (78%). Also, EPN species had higher performance in
lighter soils, which resulted in higher mortality on younger larvae than that in loamy
soil (Hassani-Kakhki et al. 2013). The effectiveness of EPN species to infect PTM
larvae and prepupa in loamy and sandy-loamy soils are important because potato
grows well in these soil textures. On the other hand, during surveys on natural
occurrence of EPNs in potato fields of the country, S. feltiae, S. carpocapsae and
H. bacteriophora were recovered (Agazadeh et al. 2010; Rahatkhah et al. 2015). In
this respect, by providing suitable conditions after EPNs application, IJs can survive,
establish and recycle, as one would expect to make a long-term regulation of PTM
during the growing season.
12.3.2.3 Onion Thrips, Thrips tabaci Lindeman, 1889 (Thysanoptera:
Thripidae)
Onion thrips, Thrips tabaci Lindeman, 1889 (Thysanoptera: Thripidae) is an important pest that has high economic importance. Control of this thrips due to their
cryptic behavior and resistance to chemical pesticides has become the major limitation in their management. Thrips pupate in the soil which makes them theoretically
reachable targets for EPNs. Hence, Saffari et al. (2013) conducted a study to
determine the pathogenicity of a native isolate of S. feltiae and two commercial
species, H. bacteriophora and S. carpocapsae against second instar larva, prepupa,
and pupa of T. tabaci under laboratory conditions. Their results indicated that
prepupa was the most vulnerable stage, and the second instar larva showed the
least susceptibility to EPNs. Heterorhabditis bacteriophora caused the highest
12 Entomopathogenic and Insect Parasitic Nematodes
489
its larvae which move in the soil, for pupation or infesting tubers. With regard to the
ability of EPNs that can actively search their hosts in a complex environment such as
soil, Hassani-Kakhki et al. (2013) assessed the effect of EPNs isolate/species on
PTM. The primary objective of their work was to evaluate the susceptibility of
different PTM stages, i.e. second (L2) and fourth instar larvae (L4) as well prepupa
to four EPN species with different foraging strategies, S. carpocapsae, [isolated IJs
from commercial product under the trade name Capsanem®], S. feltiae, S. glaseri
and H. bacteriophora FUM7 and commercial isolate [under the trade name
Larvanem®] in Petri dishes. The initial assessment on filter paper showed that
S. carpocapsae and H. bacteriophora (FUM7 and commercial) species caused the
highest mortality on both larval and prepupal stages of PTM. In general, prepupa
was the most susceptible stage while pupa had the lowest mortality.
A possible approach for control the destructive stages of PTM that infest tuber or
inter to the soil for pupation could be the application of EPNs on the soil surface.
Hence, complementary tests in soil columns, by three soil types: loamy, sandy and
sandy-loamy, containing infested tuber were established using S. carpocapsae and
H. bacteriophora (FUM7 and commercial) species. Results from this semi-field
assay indicated larval mortality induced by S. carpocapsae (88%) was higher than
those caused either by the commercial population of H. bacteriophora (79%) or by
H. bacteriophora FUM 7 (78%). Also, EPN species had higher performance in
lighter soils, which resulted in higher mortality on younger larvae than that in loamy
soil (Hassani-Kakhki et al. 2013). The effectiveness of EPN species to infect PTM
larvae and prepupa in loamy and sandy-loamy soils are important because potato
grows well in these soil textures. On the other hand, during surveys on natural
occurrence of EPNs in potato fields of the country, S. feltiae, S. carpocapsae and
H. bacteriophora were recovered (Agazadeh et al. 2010; Rahatkhah et al. 2015). In
this respect, by providing suitable conditions after EPNs application, IJs can survive,
establish and recycle, as one would expect to make a long-term regulation of PTM
during the growing season.
12.3.2.3 Onion Thrips, Thrips tabaci Lindeman, 1889 (Thysanoptera:
Thripidae)
Onion thrips, Thrips tabaci Lindeman, 1889 (Thysanoptera: Thripidae) is an important pest that has high economic importance. Control of this thrips due to their
cryptic behavior and resistance to chemical pesticides has become the major limitation in their management. Thrips pupate in the soil which makes them theoretically
reachable targets for EPNs. Hence, Saffari et al. (2013) conducted a study to
determine the pathogenicity of a native isolate of S. feltiae and two commercial
species, H. bacteriophora and S. carpocapsae against second instar larva, prepupa,
and pupa of T. tabaci under laboratory conditions. Their results indicated that
prepupa was the most vulnerable stage, and the second instar larva showed the
least susceptibility to EPNs. Heterorhabditis bacteriophora caused the highest
12 Entomopathogenic and Insect Parasitic Nematodes
489