Biosafety of Transgenic Crops to Natural Enemies of
Cotton Bollworm/Legume Pod Borer, Helicoverpa armigera
Nov 2009
To ensure sustainable deployment of transgenic insect-resistant plants, it is important that they are compatible
with other control methods, including the natural enemies. Therefore, we studied the effects of transgenic
cotton expressing Bacillus thuringiensis (Bt) toxin proteins on the parasitization of Helicoverpa armigera
Bt toxin was detected in cocoons of the parasitoid. Reduction in cocoon formation was due to early
mortality of H. armigera rather than the direct effects of Bt toxin on the parasitoid.
Effect of Bt intoxicated H. armigera larvae on the predator, Cheilomenes sexmaculatus
Plate 1. Ichneumonid, Campoletis chlorideae parasitizing Helicoverpa armigera
larva (1a), cotton aphid, Aphis gossypii (1b), and the coccinellid, Cheilomenes
sexmaculatus (1c).
Materials and Methods
H. armigera was monitored in Bt-transgenic and non-transgenic
Bt C. chlorideae, the H. armigera larvae
were reared on Bt-transgenic and non-transgenic cottons.
H. armigera
of Bt (0.05%) and untreated control diet were offered to the grubs of the coccinellid predator, C.
sexmaculatus.
Bt-transgenic cotton on the predatory coccinellid, larvae of C. sexmaculatus were
reared on A. gossypii fed on Bt-transgenic and the non-transgenic cottons (Mech 12 and RCH 2).
Fig. 1. Parasitization of Helicoverpa on transgenic and
non-transgenic cottons in farmer’s fields (1a), and effect
of Bt-transgenic cotton on cocoon formation of larval
parasitoid, Campoletis chlorideae (1b). ++ Helicoverpa
larvae fed on transgenic cottons before and after
parasitization. -- Helicoverpa larvae fed on non-transgenic
cottons.
conditions, and the effects
of Bt-transgenic cotton and
Bt CRY toxin proteins on
Campoletis chlorideae (Plate
1a), and the generalist predator,
Cheilomemes sexmaculatus
(Plate 1c) under laboratory
conditions through intoxicated H.
armigera larvae, and the cotton
aphid, Aphis gossypii (Plate 1b).
Results and Discussion
Influence of Bt-transgenic cottons on
parasitization of Helicoverpa armigera
Trichogramma spp. was greater in Bt-transgenic
than in non-transgenic cottons (Fig. 1a).
parasitism by C. chlorideae and Eriborus spp.,
and no larval-pupal tachinid parasitoids were
recorded in Bt cotton.
C. chlorideae reared on
H. armigera fed on Bt-transgenic cottons was
(Fig. 1b).
Conclusions
However, Bt
effects of Bt toxins on the natural enemies.
Bt-transgenic crops on the natural enemies are far lower than those of the
synthetic pesticides, which result in complete elimination of the natural enemies.
Acknowledgments:
C. sexmaculatus fed on H.
armigera larvae reared on Bt
intoxicated diet increased by
1.5 days (Fig. 2a, b). However,
there was no effect on adult
emergence (Fig. 2a).
Bt protein
were detected in C. sexmaculatus
larvae when fed on H. armigera
larvae raised on Bt intoxicated
Fig. 2. Development period and adult emergence of Cheilomenes
sexmaculatus fed on Helicoverpa armigera larvae reared on Bt intoxicated
Effect of Bt-transgenic cotton reared Aphis gossypii on Cheilomenes sexmaculatus
C. sexmaculatus reared on Bt-transgenic cotton fed A. gossypii increased by 1 to
1.5 days (Fig. 3a), and the adult emergence decreased by 13 to 40% (Fig. 3b).
<0.5 ppb) of Bt protein in A. gossypii and C. sexmaculatus adults, and
moderate levels (>2.5 ppb) in C. sexmaculatus larvae (Fig. 4).
Fig. 4. Detection of Bt toxins in different stages of
Cheilomenes sexmaculatus and Aphis gossypii.
Fig. 3. Development period (3a) and adult emergence (3b) of
Cheilomenes sexmaculatus reared on Bt-transgenic and non-
transgenic cotton fed Aphis gossypii.
a
a b
b c