activity after exposure to UV radiation by 67.78%, 65.31%, 59.55%, and 31.35%,
respectively. These findings suggest that combinations of natural adjuvants including molasses and lignin are as effective as chemical adjuvants such as Tinopal and
could improve PlxyGV viral activity (Dezianian et al. 2012).
Microclimate thermal conditions can also affect virulence and viral kill speed.
Moshtaghi Maleki et al. (2013), evaluated the effect of temperature (20, 26 and
30
C) on the LT 50 and LD 50 of Helicoverpa armigera MNPV in third instar larvae
of H. armigera under laboratory conditions. The LD 50 values for three
temperatures – 20, 26 and 30
C – were 3580.83, 2614.82 and 1751.62 OB/larva,
respectively. Mortality caused by viral infection increases significantly with temperature, and is especially significant in low doses. The LT 50 values for 5 Â 10
5
OB/larva viral concentration in temperatures 20, 26 and 30
C were 7.15, 6.73 and
6.58 days, respectively. Thus, temperatures in the range of 26–30
C are suitable
conditions for high mortality rate and speed.
Another limitation of viral biopesticides is their persistence in the environment.
Considering the issue of resistant formulations, Dezianian et al. (2015a), surveyed
the effect of two formulations of PlxyGV on larval mortality of P. xylostella under
natural conditions. Spray-dried, PlxyGV+ modified food starch combined with
lignin and molasses (CLM formulation) considerably increased residual activity of
PlxyGV in the environment. The CLM formulation containing 1 Â 10
13 granule/ha
after 0.5, 5, 24, 48 and 72 hours exposure in the field condition increased the residual
activity of the viral preparation by 13.7, 30.67, 42.93, 52.53 and 21.76% when
compared to unformulated virus, respectively. The CLM formulation was significantly more effective on larval mortality than KLM formulation (PlxyGV + kaolin+
lignin + molasses) after exposure to in the field condition (Dezianian et al. 2015a).
13.1.4 The Effect of Entomopathogenic Virus on Parasioids
Rabie et al. (2010), investigated the survival of Habrobracon hebetor (Say 1836)
(Hym.: Braconidae) on nucleopolyhedrovirous (NPV)-infected S. exigua larvae. In
this study, the second instar larvae of S. exigua were exposed to the under-LD 50 ,
LD 50 and over-LD 50 rate of Mamestra brassicae NPV (MbMNPV). They were able
to be parasitized by H. hebetor after 24, 48, and 72 h post-treatment. MbNPV
infection of larvae was deleterious to the survival and parasitism of H. hebetor.
The survival of H. hebetor in MbMNPV-infected S. exigua was dependent on the
interval between viral infection and parasitism. In treated larvae with a 180 PIB/mm
2
concentration of MbNPV at 72-h interval treatment, fewer adult parasitoids emerged
from infected hosts compared to 24 and 48 h post treatment. Thus, inoculation
dosage of MbNPV and timing of parasitoid release has a significant effect on the
development of H. hebetor within virus-infected hosts. Furthermore, viral biocontrol
of S. exigua may lead to substantial mortality of immature parasitoids (Rabie et al.
2010).
514
M. Mehrabadi et al.
respectively. These findings suggest that combinations of natural adjuvants including molasses and lignin are as effective as chemical adjuvants such as Tinopal and
could improve PlxyGV viral activity (Dezianian et al. 2012).
Microclimate thermal conditions can also affect virulence and viral kill speed.
Moshtaghi Maleki et al. (2013), evaluated the effect of temperature (20, 26 and
30
C) on the LT 50 and LD 50 of Helicoverpa armigera MNPV in third instar larvae
of H. armigera under laboratory conditions. The LD 50 values for three
temperatures – 20, 26 and 30
C – were 3580.83, 2614.82 and 1751.62 OB/larva,
respectively. Mortality caused by viral infection increases significantly with temperature, and is especially significant in low doses. The LT 50 values for 5 Â 10
5
OB/larva viral concentration in temperatures 20, 26 and 30
C were 7.15, 6.73 and
6.58 days, respectively. Thus, temperatures in the range of 26–30
C are suitable
conditions for high mortality rate and speed.
Another limitation of viral biopesticides is their persistence in the environment.
Considering the issue of resistant formulations, Dezianian et al. (2015a), surveyed
the effect of two formulations of PlxyGV on larval mortality of P. xylostella under
natural conditions. Spray-dried, PlxyGV+ modified food starch combined with
lignin and molasses (CLM formulation) considerably increased residual activity of
PlxyGV in the environment. The CLM formulation containing 1 Â 10
13 granule/ha
after 0.5, 5, 24, 48 and 72 hours exposure in the field condition increased the residual
activity of the viral preparation by 13.7, 30.67, 42.93, 52.53 and 21.76% when
compared to unformulated virus, respectively. The CLM formulation was significantly more effective on larval mortality than KLM formulation (PlxyGV + kaolin+
lignin + molasses) after exposure to in the field condition (Dezianian et al. 2015a).
13.1.4 The Effect of Entomopathogenic Virus on Parasioids
Rabie et al. (2010), investigated the survival of Habrobracon hebetor (Say 1836)
(Hym.: Braconidae) on nucleopolyhedrovirous (NPV)-infected S. exigua larvae. In
this study, the second instar larvae of S. exigua were exposed to the under-LD 50 ,
LD 50 and over-LD 50 rate of Mamestra brassicae NPV (MbMNPV). They were able
to be parasitized by H. hebetor after 24, 48, and 72 h post-treatment. MbNPV
infection of larvae was deleterious to the survival and parasitism of H. hebetor.
The survival of H. hebetor in MbMNPV-infected S. exigua was dependent on the
interval between viral infection and parasitism. In treated larvae with a 180 PIB/mm
2
concentration of MbNPV at 72-h interval treatment, fewer adult parasitoids emerged
from infected hosts compared to 24 and 48 h post treatment. Thus, inoculation
dosage of MbNPV and timing of parasitoid release has a significant effect on the
development of H. hebetor within virus-infected hosts. Furthermore, viral biocontrol
of S. exigua may lead to substantial mortality of immature parasitoids (Rabie et al.
2010).
514
M. Mehrabadi et al.