84 Environmental Biotechnology
programmes and thirdly, to identify more pheromones to widen the number of
phytophagous stink bug species which can be countered in this way.
As something of an aside, one interesting and somewhat unusual use has been
proposed for this technology. The Siberian mothDendrolimus superans is a
vigorous defoliating pest of northern Asian coniferous forests and, though it does
not presently occur in North America, its arrival is much feared. In an attempt to
provide a first line of defence against this potential threat to native woodlands, it
has been suggested that a blend of Z5,E7-dodecadienol and Z5,E7-dodecadienol,
which has been shown to act as a powerful sex attractant for male Siberian moths,
be deployed at US ports of entry.
However, as illustrated by the case of another pentatomid,Nezara viridula,
the southern green stink bug, the use of this approach to biological control is
not universally applicable. These insects are major agricultural pests affecting a
variety of field crops, vegetables, fruits and nuts. While it has been known for
sometime that sexually mature males produce an attractant pheromone, the active
ingredients of which have been identified, early attempts to use this knowledge
to exclude them from crops have been of only limited effectiveness. As a result,
an alternative method of Nezara control has been suggested involving the genetic
engineering of its gut symbionts to produce a reduced tolerance of environmental
stress. Preliminary work at the Agricultural Research Center, Beltsville, USA has
isolated and culturedin vitroa gram-negative bacterium from the mid-gut of the
pest insect, which appears to be a specific symbiont and has been putatively iden-
tified as a species ofYokenella. This kind of application of transgenic technology
may increasingly be the future of biological control for species which do not
respond favourably to pheromone trapping.
Not all approaches to biocontrol truly qualify as environmental biotechnolo-
gies, at least not within the frame of reference used in this book. However, where
the use of biological systems results in reduced insecticide use and thus a cor-
responding lowering of the attendant pollution potential, the net environmental
gains of the application of biotechnology are clear.
Biosubstitutions
The biosubstitution of suitable, less harmful alternatives for many of today’s
polluting substances or materials is a major potential avenue for the environ-
mentally beneficial application of biotechnology. The question of biofuels and
the major renewable contribution which organised, large-scale biomass utilisa-
tion could make to energy demands is examined in some detail in Chapter 10
and will not, therefore be repeated here. The biological production of polymers,
likewise, features in the same section on integrated biotechnology and, though
clearly distinctly germane to the present discussion, will also not appear in this
consideration. However, the other major use of mineral oils, as lubricants, is
an excellent case study of the opportunities, and obstacles, surrounding biotech