questioned. Both microbial control agents, the bacterium and the virus, have to be
ingested to exert the insecticidal activity. The interaction between Bt and HaSNPV
in biological control of H. armigera was assessed with the aim of solving the insect
resistance problems, using a low concentration of bio-insecticides and more importantly, increasing the efficiency of cotton bollworm management (Kalantari et al.
2014). Three Iranian Bt strains, KD-2, 20 and 6R, and H. armigera single polyhedrosis virus (HaSNPV) provided from the national collection of Iranian Research
Institute of Plant Protection, were employed. The virulence of Bt strains and
HaSNPV were investigated individually and in combination at different concentrations of bacterium and virus. KD-2 Bt strain and HaSNPV were highly toxic to
H. armigera. The joint use of Bt and HaSNPV led to significant differences in
H. armigera larval mortality. Depending on the concentration, all three possible
interactions, antagonism, additive, and synergism, were observed when two microbial control agents were used jointly. The application of Bt at a concentration lower
than LC 50 value in combination with HaSNPV at the concentration equal to LC 50 ,
resulted in a synergistic effect. Kalantari et al. (2014) showed that the simultaneous
application of Bt and HaSNPV adversely affected the growth and development of
H. armigera, therefore, the appropriate combination of these two microbial control
agents may increase the efficiency in H. armigera control.
The interaction between Bt and Azadirachtin, a tetranortriterpenoid compound
derived from the neem tree, Azadirachta indica, in biological control of pests have
been investigated against different insect species under laboratory and field conditions (Abedi et al. 2014; Nazarpour et al. 2014; Nouri-Ghanbalani et al. 2016). The
combination of B. thuringiensis subsp. kurstaki strain ABTS-351 and Azadirachtin
for the control of H. armigera under laboratory conditions has been assessed (Abedi
et al. 2014). The combination of Bt and Azadirachtin had a synergistic effect on the
mortality of third instar larvae of H. armigera, therefore, after field trials, the joint
use of these two insecticides can be suggested (Abedi et al. 2014).). The same results
were obtained by Nouri-Ghanbalani et al. (2016) showing synergistic interaction
between Bt and Azadirachtin on the mortality of P. interpunctella third instar larvae.
Under laboratory conditions, the combined effect of Bt and spinosad against beet
armyworm larvae, S. exigua, was studied (Hosseinizadeh and Aramideh 2014).
Combination of Bt and spinosad resulted in a high S. exigua neonate mortality,
therefore, the simultaneous application of Bt and spinosad is recommended in the
biological control of beet armyworm (Hosseinizadeh and Aramideh 2014).
The susceptibility of Colorado potato beetle larvae, L. decemlineata (Col.:
Chrysomelidae), to B. thuringiensis subsp. tenebrionis alone and in combination
with henna powder and cinnamon extract were investigated (Ghassemi-Kahrizeh
et al. 2014). The synergistic effect on L. decemlineata mortality was observed
following combination of both Bt with henna powder and also Bt with cinnamon
extract.
The compatibility of Bt application simultaneously with chemical insecticides has
been also studied. The interaction between B. thuringiensis subsp. kurstaki with
abamectin, azadirachtin, indoxacarb, chlorantraniliprole, dichlorvos and
metaflumizone, in the control of T. absoluta were investigated (Amizadeh et al.
10 Progress on the Bacterium Bacillus thuringiensis and Its. . .
427
ingested to exert the insecticidal activity. The interaction between Bt and HaSNPV
in biological control of H. armigera was assessed with the aim of solving the insect
resistance problems, using a low concentration of bio-insecticides and more importantly, increasing the efficiency of cotton bollworm management (Kalantari et al.
2014). Three Iranian Bt strains, KD-2, 20 and 6R, and H. armigera single polyhedrosis virus (HaSNPV) provided from the national collection of Iranian Research
Institute of Plant Protection, were employed. The virulence of Bt strains and
HaSNPV were investigated individually and in combination at different concentrations of bacterium and virus. KD-2 Bt strain and HaSNPV were highly toxic to
H. armigera. The joint use of Bt and HaSNPV led to significant differences in
H. armigera larval mortality. Depending on the concentration, all three possible
interactions, antagonism, additive, and synergism, were observed when two microbial control agents were used jointly. The application of Bt at a concentration lower
than LC 50 value in combination with HaSNPV at the concentration equal to LC 50 ,
resulted in a synergistic effect. Kalantari et al. (2014) showed that the simultaneous
application of Bt and HaSNPV adversely affected the growth and development of
H. armigera, therefore, the appropriate combination of these two microbial control
agents may increase the efficiency in H. armigera control.
The interaction between Bt and Azadirachtin, a tetranortriterpenoid compound
derived from the neem tree, Azadirachta indica, in biological control of pests have
been investigated against different insect species under laboratory and field conditions (Abedi et al. 2014; Nazarpour et al. 2014; Nouri-Ghanbalani et al. 2016). The
combination of B. thuringiensis subsp. kurstaki strain ABTS-351 and Azadirachtin
for the control of H. armigera under laboratory conditions has been assessed (Abedi
et al. 2014). The combination of Bt and Azadirachtin had a synergistic effect on the
mortality of third instar larvae of H. armigera, therefore, after field trials, the joint
use of these two insecticides can be suggested (Abedi et al. 2014).). The same results
were obtained by Nouri-Ghanbalani et al. (2016) showing synergistic interaction
between Bt and Azadirachtin on the mortality of P. interpunctella third instar larvae.
Under laboratory conditions, the combined effect of Bt and spinosad against beet
armyworm larvae, S. exigua, was studied (Hosseinizadeh and Aramideh 2014).
Combination of Bt and spinosad resulted in a high S. exigua neonate mortality,
therefore, the simultaneous application of Bt and spinosad is recommended in the
biological control of beet armyworm (Hosseinizadeh and Aramideh 2014).
The susceptibility of Colorado potato beetle larvae, L. decemlineata (Col.:
Chrysomelidae), to B. thuringiensis subsp. tenebrionis alone and in combination
with henna powder and cinnamon extract were investigated (Ghassemi-Kahrizeh
et al. 2014). The synergistic effect on L. decemlineata mortality was observed
following combination of both Bt with henna powder and also Bt with cinnamon
extract.
The compatibility of Bt application simultaneously with chemical insecticides has
been also studied. The interaction between B. thuringiensis subsp. kurstaki with
abamectin, azadirachtin, indoxacarb, chlorantraniliprole, dichlorvos and
metaflumizone, in the control of T. absoluta were investigated (Amizadeh et al.
10 Progress on the Bacterium Bacillus thuringiensis and Its. . .
427