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cost of applying herbicides. Thus for these growers the demand is now for effective
site-specific weed management systems.
Given the potential cost savings of site-specific versus whole field weed control
there is now considerable effort being focussed on the development of weed detec-
tion and mapping systems. The capacity to accurately detect and map low-density
weed populations within a crop creates the opportunity for the use of range of alter-
nate control tactics. In low weed density situations, because of the small areas
involved, and therefore, the reduced impact on crop yields, detected weeds can be
aggressively targeted. For example, non-selective herbicides, tillage treatments,
even hand weeding all become viable options. Additionally, the ability to strategi-
cally target low weed densities creates the potential for the introduction of more
novel and unique weed control technologies such as electrocution (Vigneault et al.
1990 ), flaming (Hoyle et al. 2012 ), microwaves (Brodie et al. 2012 ), infrared
(Ascard 1998 ) and lasers (Marx et al. 2012 ). There is now considerable investment
in the area of weed identification and mapping occurring on many fronts ranging
from vehicle mounted to UAV and even satellite systems.
6 Conclusion
Many tools are currently available for weed management in dryland cropping sys-
tems. Additionally, there opportunities for the development of new options and
techniques particular in the advent of automatipsite-specific However, all tools have
both costs and benefits, and it is the balance that will determine their use within
particular farming systems. Herbicides are viewed as effective, relatively cheap
tools compared with some other practices, and while their benefits are significant,
the failure to integrate herbicides with other methods has led to their downfall in
many areas due to herbicide resistance.
Considerable opportunities exist for designing cropping systems that exhibit
IWM and are economically and biologically sustainable. These will become increas-
ingly important as herbicide resistance becomes more widespread. The length of the
system and the types of crops and control methods are generally more extensive
than currently used by many farmers. For example, the ability to grow niche crops
such as durum wheat requires high fertility systems and very low levels of weeds if
grain protein and yield are to be maximised. Practices such as green manuring of
legume crops, grown specifically to harvest nitrogen in the year preceding the
durum crop, provide an excellent way to achieve high levels of weed control and the
quality standards required for the crop.
Do farmers practice IWM? In the main, herbicide technology dominates weed
management strategies, although many farmers implement, deliberately or other-
wise, some IWM principles. However, only when confronted with problems, such
as herbicide resistance or rapidly increasing populations of recalcitrant weeds, is
serious attention given to alternative weed management tools.
M. Wa lsh