Bushland Weeds Manual - Environmental Weeds Action Network

6
Chapter 2 Managing Weeds in Bushland
Regional information
Australia is divided up into a series of natural regions.
The Swan Coastal Plain and the Wheatbelt are two
such regions within Western Australia from where case
studies in the text have been drawn. An understanding
of a bushland’s natural values in relation to others in
the region provides information on the area’s
significance. For example, a bushland may be
representative of the more common or rare plant
communities in the region. It is important to note that
the rarest communities (Threatened Ecological
Communities) and flora (Declared Rare Flora – DRF),
are protected by laws, either at the state (DRF) or the
federal (communities) level. Bush Forever, Volume 2 –
Directory of Bush Forever Sites (Government of
Western Australia 2000) catalogues information on
regionally significant bushland on the Swan Coastal
Plain. It provides details on the area of the bushland
type that remains uncleared in the region, how much is
in conservation reserves, the quality and condition of
those bushlands, and where similar bushland can be
found. This type of information is important in
providing a focus for weed management work, and in
gaining an understanding of bushland values that
require protection (Keighery et al. 1998).
Note: Bushland restoration carried out where rare flora occurs
requires a permit from the Department of Conservation and Land
Management (DCLM).
Developing a weed
management program
Resources for bushland restoration work are generally
limited. It is critical that these resources are carefully
targeted through strategies that prioritise management
actions, based on a knowledge of the bushland area
and the weeds that are impacting on it. Central to
these strategies are a series of principles that are
fundamental to successful weed management. Many of
the case studies throughout this manual demonstrate
the application of these principles:
• Contain the spread of serious weeds and protect
intact bushland. Consider the impacts of serious
weeds on rare flora and rare plant communities.
• Prevent new weed species establishing.
• Consider restoration of degraded edges. Usually
this is of lower priority than protection of good
areas. Often though, degraded edges harbour
serious weeds, providing a source of propagules
that continually disperse into intact areas.
Implementation – taking an
integrated approach
Prevent new weeds from establishing
• Clean tools, boots, equipment and machinery
between jobs to reduce risk of spread
between sites.
• Practise soil hygiene.
• Check paving materials before bringing on to a
site, particularly limestone, for weed seed and
only acquire from accredited clean sources. Black
Flag (Ferraria crispa), Geraldton Carnation Weed
(Euphorbia terracina) and Pretty Betsy
(Centranthus rubra) to name a few have been
introduced to various bushland sites around Perth
in paving materials.
• Avoid bringing soil or mulch from elsewhere into
bushland.
• Know the plants of your bushland (native and
introduced) and immediately remove infestations
of any new weeds. This is important at individual
sites but also at a regional and state level.
See case study 5.2 on Holly-leafed Senecio
(Senecio glastifolius) a recent invader to south west
Western Australia.
Limit the spread of established weeds
• Target small populations in good bush and the
outliers of dense infestations - use the maps
(Box 2.1).
• Keep soil disturbance to a minimum. Disturbance
favours the establishment of many weeds. It brings
buried weed seed to the surface thereby releasing
dormancy, and creates favourable conditions for
the germination of wind dispersed weed seed.
• Avoid working in areas where weeds are actively
shedding seed.
• Post-fire conditions (space, light and high nutrient
availability) often favour establishment of weeds.
Weed control in the season immediately following
fire will prevent seed set in established weeds and
reduce germinating weed seedlings. It will limit the
inevitable spread of many serious bushland weeds
through the post-fire landscape.
See Box 4.2 on fire and cormous and bulbous weeds,
Box 5.1 on the weeds that move in with soil
disturbance, and Box 3.5 on limiting the spread of
Perennial Veldgrass following fire.