mean mortality of infected 2nd, 3rd, and 4th instar larvae were 74.4, 42.77, and
11.11%, respectively. Thus, older larvae have lower sensitivity to MbNPV infection.
In another study, the effect of Taiwanese strain of Plutella xylostella granulovirus
(PlxyGV) (Baculoviridae), as a natural enemy on P. xylostella was surveyed. The
experiment was carried out with seven concentrations. The LC 50 and LC 90 values of
Taiwanese strain of PlxyGV for the second instar larvae of the cabbage moth were
calculated as 448.58 and 715.77 granules/mm
2 , respectively. The LT 50 values for
this PlxyGV strain when applied at concentrations of 749.89 and 1883.65 granule/
mm
2 were 6.04 and 6.68 days, respectively (Fahimi et al. 2008b).
Magholi et al. (2014), surveyed the insecticidal activity of a baculovirus
(HaNPV) against 2nd instar larvae of P. xylostella. LC 25 , LC 50 , and LC 75 were
2.2 Â 10
3 , 3.8 Â 10
4 and 6.6 Â 10
5 OB/ml, respectively. Median lethal time (LT 50 )
decreased from 114.24 to 106.05 h with decreasing larval age. Larval development
time and pupal weight were not affected by the different concentration of HaNPV.
There were, however, significant differences between the pupal rate and adult
emergence in treated larvae with different concentration.
Dezianian et al. (2015b) evaluated the pathogenicity of Plutella xylostella
Granulovirus (PlxyGV) on the P. xylostella larvae. Bioassay results showed that
larval mortality was significantly influenced by larval instar and viral concentrations.
The larval mortality increased with increasing viral concentrations and decreased for
older instars. The LC 50 of the virus on the second instar larvae was estimated as
1.39 Â 10
6 granules/ml. The measured LT 50 values were between 3.81–6.95,
4.97–9.74 and 5.15–9.41 days for first, second and the third instar larva, respectively. The high specificity and virulence of PlxyGV supports its suitability as an
appropriate candidate for use within an Integrated Pest Management (IPM) program
targeting P. xylostella.
13.1.2.5 Bombyx mori
Grasseri is one of the most important diseases of silkworm, Bombyx mori (Linnaeus
1758) (Lep.: Bombycidae) with a significant yield loss caused by nuclear polyhedrosis viruses (NPV) (Etebari et al. 2007). This virus decreases protein content in the
infected larvae. Thus, identification of resistant populations of B. mori is an important step in lowering the disease damage. Seidavi et al. (2004), performed an
experiment to compare 21 new lines of silkworm populations including 11 Japanese
and 10 Chinese lines in natural conditions and infected environments against nuclear
polyhedrosis virus. The number of surviving larvae, surviving pupae, pupation rate,
cocoon weight, shell weight and shell ratio was measured. The results showed that
Chinese lines were more susceptible to NPV infection in infected conditions than
Japanese lines. Also, the effect of viral infection on silk production potential of
individuals was not significant in most lines. Larval resistance to virus could be
transmitted to sensitive lines and this characteristic could be applied for improving
high productivity lines (Seidavi et al. 2004).
512
M. Mehrabadi et al.
11.11%, respectively. Thus, older larvae have lower sensitivity to MbNPV infection.
In another study, the effect of Taiwanese strain of Plutella xylostella granulovirus
(PlxyGV) (Baculoviridae), as a natural enemy on P. xylostella was surveyed. The
experiment was carried out with seven concentrations. The LC 50 and LC 90 values of
Taiwanese strain of PlxyGV for the second instar larvae of the cabbage moth were
calculated as 448.58 and 715.77 granules/mm
2 , respectively. The LT 50 values for
this PlxyGV strain when applied at concentrations of 749.89 and 1883.65 granule/
mm
2 were 6.04 and 6.68 days, respectively (Fahimi et al. 2008b).
Magholi et al. (2014), surveyed the insecticidal activity of a baculovirus
(HaNPV) against 2nd instar larvae of P. xylostella. LC 25 , LC 50 , and LC 75 were
2.2 Â 10
3 , 3.8 Â 10
4 and 6.6 Â 10
5 OB/ml, respectively. Median lethal time (LT 50 )
decreased from 114.24 to 106.05 h with decreasing larval age. Larval development
time and pupal weight were not affected by the different concentration of HaNPV.
There were, however, significant differences between the pupal rate and adult
emergence in treated larvae with different concentration.
Dezianian et al. (2015b) evaluated the pathogenicity of Plutella xylostella
Granulovirus (PlxyGV) on the P. xylostella larvae. Bioassay results showed that
larval mortality was significantly influenced by larval instar and viral concentrations.
The larval mortality increased with increasing viral concentrations and decreased for
older instars. The LC 50 of the virus on the second instar larvae was estimated as
1.39 Â 10
6 granules/ml. The measured LT 50 values were between 3.81–6.95,
4.97–9.74 and 5.15–9.41 days for first, second and the third instar larva, respectively. The high specificity and virulence of PlxyGV supports its suitability as an
appropriate candidate for use within an Integrated Pest Management (IPM) program
targeting P. xylostella.
13.1.2.5 Bombyx mori
Grasseri is one of the most important diseases of silkworm, Bombyx mori (Linnaeus
1758) (Lep.: Bombycidae) with a significant yield loss caused by nuclear polyhedrosis viruses (NPV) (Etebari et al. 2007). This virus decreases protein content in the
infected larvae. Thus, identification of resistant populations of B. mori is an important step in lowering the disease damage. Seidavi et al. (2004), performed an
experiment to compare 21 new lines of silkworm populations including 11 Japanese
and 10 Chinese lines in natural conditions and infected environments against nuclear
polyhedrosis virus. The number of surviving larvae, surviving pupae, pupation rate,
cocoon weight, shell weight and shell ratio was measured. The results showed that
Chinese lines were more susceptible to NPV infection in infected conditions than
Japanese lines. Also, the effect of viral infection on silk production potential of
individuals was not significant in most lines. Larval resistance to virus could be
transmitted to sensitive lines and this characteristic could be applied for improving
high productivity lines (Seidavi et al. 2004).
512
M. Mehrabadi et al.