Reducing agroecosystem vulnerability to weed invasion - Invasive Plants: Ecological and Agricultural Aspects - page 178

an effective ecological weed management technique [90], does not approach
species diversity levels in natural ecosystems. A compromise to high species
diversity in space is to maximize species diversity in time; this is best accom-
plished by ensuring that a given field is subjected to diverse rotational crops.
Diverse crop rotations are probably the most effective management tool in
maintaining crop health and limiting weed invasion opportunities.
In the future, very clean (near weed-free) fields may not be considered
acceptable [91]. We might do well to alter our view of what is desirable: from
an “ultra-clean” crop with no weeds visible to a more species-rich field with
sub-threshold communities of weeds. This approach could be termed “ecolog-
ical weed management” [92]. Pest management in disciplines other than weed
science may benefit from a few weeds [93, 94]. For example, root maggot
( Delia spp) egg deposition and larval damage were reduced in plots where
weeds were left in canola longer than the period recommended for optimal
yields [95]. Combining and applying the techniques discussed above, reducing
herbicide use, and tolerating low infestations of weeds may be the most sus-
tainable form of weed management over the long-term. Ignoring ecological
weed management techniques and maintaining current herbicide application
practices will ensure a higher frequency of weed invasions of the resistant type
[96, 97].
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