Agriculture Reference
In-Depth Information
cultivation of Bt crops on earthworms
The laboratory, greenhouse, and field studies outlined above indicate that cultivation of
Bt
crops, including maize expressing Cry1Ab or Cry3Bb1 and cotton expressing Cry1Ac, have
no deleterious effects in soil on numbers or populations of earthworms, and that differ-
ences in agricultural practices (e.g., herbicide applications) associated with the cultivation
of GM crops may be more important to earthworm health and ecosystem function than
the
Bt
proteins associated with GM crops. Nevertheless, continued monitoring for effects
of
Bt
plants on earthworms would be useful, especially with the ever-increasing hectarage
dedicated to the cultivation of
Bt
crops across the globe and the continued development of
new and different types of
Bt
plants. Because earthworms do not appear to be affected by
most
Bt
plants examined thus far, in future studies, the research focus should be narrowed
to evaluate earthworm species based on their association with a particular
Bt
crop or their
importance to ecosystem processes in a given area (Zeilinger et al., 2010).
Microarthropods, including isopods (pillbugs, woodlice), collembolans (springtails), and
mites, are other organisms in the soil ecosystem that may be affected by the cultivation
tion of plant material may be compromised by changes in the structure, chemistry, and
other properties of soil by Cry proteins deposited in soil from transgenic plant biomass
or root exudates. Despite being more closely related to target insect pest populations (e.g.,
Lepidoptera, Coleoptera, Diptera) than the other soil organisms already discussed, most
microarthropods, including the woodlouse
Porcellio scaber
(Escher et al., 2000; Pont and
Nentwig, 2005), the pillbugs
Armadillidium nastum
and
Trachelipus rathkii
(Clark et al., 2006),
the collembolans
Folsomia candida
(Sims and Martin, 1997; EPA, 2001b; Bakonyi et al., 2006;
Clark and Coats, 2006; Bakonyi et al., 2011),
Xenylla griesea
(Sims and Martin, 1997), and
Protaphorura armata
(Heckmann et al., 2006), as well as natural populations of collembolans
(Lang et al., 2006; de Vaufleury et al., 2007; Priestley and Brownbridge, 2009), have shown no
adverse effects in soil from the cultivation of
Bt
Cry1Ab maize, consumption of
Bt
Cry1Ab
maize plant material, or consumption of purified Cry1Ab protein in studies in microcosms
and in the field. Similarly, there was no negative effect of transgenic
Bt
cotton expressing
Cry1Ab or Cry1Ac or
Bt
potato expressing Cry3A on
F. candida
(Yu et al., 1997; EPA, 2001b)
and also no effect of
Bt
potato on the number of eggs and body length of the mite
Oppia
nitens
(Yu et al., 1997). In laboratory experiments in which the orbatid mite
Scheloribates
praeincisus
was grown in rearing chambers and fed
Bt
cotton leaves (Bollgard; Cry1Ac),
non-
Bt
cotton leaves, and the
Bt
biopesticide Dipel
®
(containing spores of
B. thuringiensis
var.
kurstaki,
HD-1, coding for the expression of the insecticidal d-endotoxin Cry1Ab), there
was no effect on survival or development of adult or immature mites or an effect on food
consumption (Oliveira et al., 2007). Cultivation of
Bt
maize expressing Cry3Bb1 showed
no deleterious effects on the numbers of collembolans or mites in natural populations of
field soil (Al-Deeb et al., 2003). In a field experiment in which litterbags containing plant
material from nine different
Bt
(Cry1Ab, Cry3Bb1) and non-
Bt
maize lines were buried in
soil, there was no difference in decomposer communities (Collembola, Acari, and 12 taxa
of other arthropods) or degradation rate between the different cultivars (Honemann et
al., 2008). When the effects of individual purified proteins were tested (Cry1Ab, Cry2A,
Cry1Ac, Cry3A) in a feeding study over 21 days in Petri dish microcosms, there were no
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