Biology Reference
In-Depth Information
Chapter 8
Weed Invasions in Western Canada Cropping
Systems
K. Neil Harker, Robert E. Blackshaw, Hugh J. Beckie,
and John T. O'Donovan
Abstract Agricultural ecosystem weeds can be invasive species. On the Canadian
Prairies, the vast majority of weeds that annually invade crops and interfere with
crop production are self-sustaining, non-native species that have spread over large
areas. Weeds have vulnerabilities that can be exploited by combining optimal
agronomic practices in addition to herbicide application. Some of these practices
include competitive cultivars, relatively high crop seed rates, and strategic fertilizer
placement. Prairie weeds have been reduced in numbers by the consistent use of
herbicides, but herbicide resistance is now a major challenge. Weed resistance and
other shifting crop production or environmental factors may significantly alter inva-
sive weed dynamics and crop-weed interactions, and will undoubtedly pose future
challenges to crop producers. These and other challenges can be countered by
reducing soil disturbance and diversifying cropping systems that combine several
synergistic components. There is a need for the implementation of true integrated
crop, weed, and pest management systems that are multi-disciplinary. The common
alien weed species that persistently invade Prairie cropland each year will not be
subdued over the long term in the absence of such systems.
Keywords Alien species ￿ Direct seeding ￿ Herbicide resistance ￿ Integrated weed
management ￿ Tillage
8.1 Introduction
In Canada and many other countries, increasing attention is being focused on assessing
the present and future risks and consequences of invasive alien (non-indigenous) plant
species. Invading alien species can lower crop yields, cause export market loss and/or
commodity devaluation, reduce the quality of crop- and rangelands, and lead to the
K.N. Harker ( ), R.E. Blackshaw, H.J. Beckie, and J.T. O'Donovan
Agriculture and Agri-Food Canada, Lacombe Research Centre, 6000 C & E Trail, Lacombe,
AB, Canada T4L 1W1
harkerk@agr.gc.ca
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