Contents - Faperta

Transgenic Resistance to Insects: Interactions with Nontarget Organisms 345
nontarget species, and (5) conduct fi eld trials to compare the relative effect of transgenic
plants and current management practices such as pesticide use on selected species.
Influence of Transgenic Crops on Diversity of Nontarget Organisms
One of the major concerns of transgenic crops is their effects on nontarget organisms,
about which little is known at the moment. Herbivores, detritivores, and many of their
predators and parasitoids in arable systems are sensitive to changes in the environment,
including weed communities that result from the introduction of genetically modifi ed
herbicide-tolerant crops (Sharma et al., 2002; Hawes et al., 2003). The information that use
of genetically modifi ed corn may have toxic effects on larvae of the monarch butterfl y,
Danaus plexippus (L.) (Losey, Raynor, and Carter, 1999; Obrycki et al., 2001), has generated a
huge amount of public debate. However, several studies have subsequently revealed that
the impact of the current Bt maize varieties on monarch butterfl y populations is negligible
(Sears et al., 2001; Gatehouse, Ferry, and Raemaekers, 2002). Wraight et al. (2000) concluded
that there is no relationship between mortality of Papilio polyxenes Fab., and pollen deposition
from transgenic maize on its host plants. Pollen from the transgenic plants failed to
cause any mortality under laboratory conditions. An assessment of the impact of Bt cotton
pollen on two important economic insects, the Chinese tussah silkworm, Antheraea pernyi
(Guer.) and the mulbery silkworm, Bombyx mori L., has also been conducted, and it was
concluded that the adverse effect is negligible (Wu, Peng, and Jia, 2003). Transgenic pollen
prolonged duration of fi rst-instar larvae of silkworm, B. mori, compared with the nonpollen
treatment, but were not signifi cantly different from those fed with pollen from nontransgenic
cotton or maize (Li et al., 2002). Body weight of the third-instars fed on transgenic
pollen was signifi cantly more than that of the controls. Consequently, it was considered
that pollen from transgenic insect-resistant cotton and maize has negligible adverse effects
on the growth and development of the silkworm.
There were no differences in abundance of aerial fauna, including Aphididae,
Cicadellidae, Araneae, and Coleoptera (Chrysomelidae, Coccinellidae, and Staphylinidae),
and other insects living in close contact with these, or with the European corn borer,
Ostrinia nubilalis (Hubner), such as hymenopteran parasitoids, and Syrphidae in isogenic
transgenic maize (Lozzia, 1999). The biodiversity of the carabid communities was quite low
for both types of maize and no signifi cant differences were found in any of the indices
analyzed. Bt-maize has no adverse effects on nontarget arthropod communities (Bourguet
et al., 2002). Numbers of nontarget arthropods such as aphids [Metopolophium dirhodum
(Walker.), Rhopalosiphum padi (L.), and Sitobion avenae (F.)], bug, Orius insidiosus (Say), syrphid,
Syrphus corollae (Fab.), ladybird beetle, Coccinella septempunctata L., lacewing, C. carnea,
thrips, and hymenopteran parasitoids did not differ between the Bt and non-Bt maize.
However, thrips were more abundant on Bt maize at one site than in non-Bt maize (Bourguet
et al., 2002). A trend towards a community effect on fl ying arthropods has been observed,
with lower abundance of adult Lepidoptera, fl ies in the families Lonchopteridae,
Mycetophilidae, and Syrphidae; and the hymenopteran parasitoids belonging to
Ceraphronidae (Candolfi et al., 2004). The effects were weak and restricted to two sampling
dates corresponding to anthesis. However, a signifi cant reduction was observed on
the community of plant dwellers with insecticides, such as Karate, Xpress, and Delfi n. Karate
and Xpress showed a prolonged effect on soil dwellers (Candolfi et al., 2004). Larvae of