13.1.5 Combination Virus with Other Agents
Marzban et al. (2010), tested Bacillus thuringiensis (Bt) toxins combined with
cytoplasmic polyhedrosis virus on mortality rate of H. armigera. In this study, the
effects of interactions between Cry1Ac toxin of B. thuringiensis and Helicoverpa
armigera Cytoplasmic polyhedrosis virus (HaCPV) on the first and third instar
larvae of H. armigera were evaluated in the laboratory. When the first instar larvae
was exposed to a combination of Bt and HaCPV (6 Â 10
6 , 1 Â 10
7 , and 3 Â 10
7
OB/ml) on cotton leaf discs, the effect on mortality was additive. When the larvae
was exposed to a combination of Cry1Ac (0.3, 0.9, 2.7, or 8.1 μg/g) and the same
concentrations of HaCPV, the effect on mortality was additive except for the
combination of 0.3 μg/g of Cry1Ac and HaCPV which had a synergistic effect.
The third instar larvae had similar results with the first instar larvae. Overal, delayed
larval growth and development as well as pupation and pupal weight decreased
when larvae fed on an artificial diet containing Cry1Ac and HaCPV or transgenic Bt
cotton leaf discs especially for first instar larvae.
In another study, the interaction of Bacillus thuringiensis subsp. kurstaki and
Helicoverpa armigera single nucleopolyhedrovirus (HaSNPV) on the survival of
second instar P. xylostella larvae was evaluated under laboratory conditions. The
exposure of second instar larvae to a combination of HaSNPV (2.3 Â 10
3 , 3.8 Â 10
4 ,
and 6.6 Â 10
5 OB/ml) and B. thuringiensis subsp. kurstaki (2.4 Â 10
1 , 3.4 Â 10
3 ,
and 4.7 Â 10
5 spore/ml), produced an additive effect on the efficiency of most
combinations. A synergistic effect was observed when 2.4 Â 10
1 Bt was combined
with 2.3 Â 10
3 OB/ml HaSNPV. Also, population rate, pupal weight, and emergence
rate of adults decreased. The LT 50 values negatively correlated with B. thuringiensis
and HaSNPV concentrations (Magholli et al. 2013).
In a similar study, Kalantari et al. (2013) surveyed the effects of Bacillus
thuringiensis isolates and HaSNPV in combination and individually on
H. armigera larvae. Combined use of Bt (3 Â 10
6 spore/ml) and HaSNPV
(9.2 Â 10
3 OB/ml) had a synergistic effect on larval mortality. The obtained results
indicated a combination of the lowest Bt concentration and the highest HaSNPV
concentration had synergistic effect on H. armigera second instar larvae.
Assemi et al. (2013a), surveyed the efficacy of different geographical isolates of
HaNPV on biological control of H. armigera. In this research, two local strains (A,
B) of H. armigera nucleopolyhedrovirus (HaNPV) were collected from infected
H. armigera larvae in tobacco fields of north Iran. To maximize the persistence of
HaNPV, various adjuvants were evaluated such as neem, henna powder, soybean
flour, maize flour, boric acid, and diflubenzuron. Here, the viral concentration was
1 Â 10
5 OB/ml. The results indicated that a combination of diflubenzuron + virus B
and diflubenzuron + virus A caused 85.41 and 82.4% mortality, respectively.
13 Insect Pathogenic Viruses, Microsporidians and Endosymbionts
515
Marzban et al. (2010), tested Bacillus thuringiensis (Bt) toxins combined with
cytoplasmic polyhedrosis virus on mortality rate of H. armigera. In this study, the
effects of interactions between Cry1Ac toxin of B. thuringiensis and Helicoverpa
armigera Cytoplasmic polyhedrosis virus (HaCPV) on the first and third instar
larvae of H. armigera were evaluated in the laboratory. When the first instar larvae
was exposed to a combination of Bt and HaCPV (6 Â 10
6 , 1 Â 10
7 , and 3 Â 10
7
OB/ml) on cotton leaf discs, the effect on mortality was additive. When the larvae
was exposed to a combination of Cry1Ac (0.3, 0.9, 2.7, or 8.1 μg/g) and the same
concentrations of HaCPV, the effect on mortality was additive except for the
combination of 0.3 μg/g of Cry1Ac and HaCPV which had a synergistic effect.
The third instar larvae had similar results with the first instar larvae. Overal, delayed
larval growth and development as well as pupation and pupal weight decreased
when larvae fed on an artificial diet containing Cry1Ac and HaCPV or transgenic Bt
cotton leaf discs especially for first instar larvae.
In another study, the interaction of Bacillus thuringiensis subsp. kurstaki and
Helicoverpa armigera single nucleopolyhedrovirus (HaSNPV) on the survival of
second instar P. xylostella larvae was evaluated under laboratory conditions. The
exposure of second instar larvae to a combination of HaSNPV (2.3 Â 10
3 , 3.8 Â 10
4 ,
and 6.6 Â 10
5 OB/ml) and B. thuringiensis subsp. kurstaki (2.4 Â 10
1 , 3.4 Â 10
3 ,
and 4.7 Â 10
5 spore/ml), produced an additive effect on the efficiency of most
combinations. A synergistic effect was observed when 2.4 Â 10
1 Bt was combined
with 2.3 Â 10
3 OB/ml HaSNPV. Also, population rate, pupal weight, and emergence
rate of adults decreased. The LT 50 values negatively correlated with B. thuringiensis
and HaSNPV concentrations (Magholli et al. 2013).
In a similar study, Kalantari et al. (2013) surveyed the effects of Bacillus
thuringiensis isolates and HaSNPV in combination and individually on
H. armigera larvae. Combined use of Bt (3 Â 10
6 spore/ml) and HaSNPV
(9.2 Â 10
3 OB/ml) had a synergistic effect on larval mortality. The obtained results
indicated a combination of the lowest Bt concentration and the highest HaSNPV
concentration had synergistic effect on H. armigera second instar larvae.
Assemi et al. (2013a), surveyed the efficacy of different geographical isolates of
HaNPV on biological control of H. armigera. In this research, two local strains (A,
B) of H. armigera nucleopolyhedrovirus (HaNPV) were collected from infected
H. armigera larvae in tobacco fields of north Iran. To maximize the persistence of
HaNPV, various adjuvants were evaluated such as neem, henna powder, soybean
flour, maize flour, boric acid, and diflubenzuron. Here, the viral concentration was
1 Â 10
5 OB/ml. The results indicated that a combination of diflubenzuron + virus B
and diflubenzuron + virus A caused 85.41 and 82.4% mortality, respectively.
13 Insect Pathogenic Viruses, Microsporidians and Endosymbionts
515