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III. GENERAL STRATEGY FOR WEED CONTROL
Parkcare and Landcare groups always need a strategy framework within which to optimize their efforts towards weed control and bush regeneration. The suggestions outlined below stem mainly from the ACT Bushcare Manual (Chapter 7), the Pest Management Manual (Chapter 1), the works of Bradley and Buchanan cited in the Introduction, and experience on the ground plus discussion with colleagues. The aim of weed control is basically to facilitate bush regeneration; so weed control activity is subservient to the overall process of bush regeneration. The extent to which even severely degraded and weed-infested bushland can recover, if weeds are simply and carefully removed, is astounding. This was the basic ecological and biological principle discovered by the Bradley sisters, who worked in Sydney bushlands. The Bradley method involves careful weeding, with minimal soil disturbance, and allowing the bush to regenerate naturally. It includes a strategy of starting with areas with well-established indigenous flora and less, or not excessive, weed infestation. It implies working outwards from relatively less-infested areas. A general principle derived from this approach is to aim, first of all, to continue to control weeds by periodic weeding in areas already given a primary weeding; and in a new area being tackled, to start with less-infested portions of that area. Return visit. After the first weeding (primary weeding) of an infested area, common-sense and common experience teach how important it is to come back within a few days, weeks or months to catch weeds that were missed or grew up since the primary weeding. An effectively weeded area can rather rapidly be re-infested if even a few prolific seed-bearing plants are missed. About a month later may usually be a good time to return; experience gives guidance on what is the suitable interval, depending on season, weed-type etc.. If it is a seed-bearing herb close to the flowering season, re-visit between a week and a month is likely to be best, e.g. for Paterson�s curse. For woody weeds the time for return could be between a month and a year. Focus on worst-affected areas. In the writers� experience often the principle adopted � which also works reasonably well � seems almost the opposite to the Bradley method. Many parkcare/landcare programmes often tackle first the most heavily infested areas. There are some advantages to this approach: Foci of weed multiplication and dissemination are immediately reduced Weed-infested areas that are eyesores to the public are immediately reduced There is much to show immediately as progress towards bush regeneration. On the whole this is the general approach the writers have adopted in their areas of responsibility in recent years. Often gullies, for instance, are heavily infested especially with woody weeds. This approach is still in line with the principle of the Bradley method, of allowing the bush to regenerate by simply clearing away the weeds. We are also fortunate in the Canberra region in that our worst weed infestations are relatively less affected in comparison with the forest of weeds in much of the North Sydney bushland, on which the Bradley sisters worked. A number of factors may however impinge on this general principle of tackling worst-affected areas first, causing parkcare/landcare organizers to modify the areas or sequence of actions: Ecologically sensitive areas e.g. eroded or bare areas Areas containing particularly important flora or fauna Areas that are much frequented and in the public view, e.g. along walking trails, around lookout points etc � deference to recreational/aesthetic aspects Weeds that can be relatively easily, effectively and sustainably removed Areas that will not be significantly damaged by the weeding process Weeds and areas that can be tackled without use of chemicals harmful to surrounding natural vegetation Weeds needing time-priority because flowering/seeding are imminent Problems or opportunities due to natural or man-made accidents, e.g. fire � enabling (for instance) dense thickets of woody weeds to be finished off; or causing emergence of dense new weed infestations e.g. thistle rosettes, fleabane, great mullein. Some very serious weed problems it may not be possible to address immediately, e.g. blackberries following a fire: although the surface infestation may be largely gone, there will be an underlying deep root system that will continue to send up shoots; it is better to wait until a large volume of leafy growth has occurred and then specific anti-blackberry herbicides will be more effective. In general woody weed control is not strongly affected by seasonal factors, although cut-stump and herbicide application will be less effective in winter and mid-summer than at other times. On the other hand control of herbaceous weeds is greatly affected by the biological cycle: some herbaceous weeds may be best tackled at the rosette or young-plant stage (e.g. pulling or chipping out, dabbing or spraying of herbicide). others may be caught at the early flowering stage e.g. slashing of saffron thistles. others may be better controlled later by cutting and bagging seedheads, e.g. matured thistles, great mullein etc. Because of these time-imperatives, work on herbaceous weeds is often a sort of �fire-fighting� process, tackling one type of weed after another in sequence as they begin to flower and go to seed. Late autumn, winter and early spring are often looked on as �slack� times but there is really much to do at these times e.g. chipping out rosettes of larger thistles, Paterson�s curse etc. Most of the herbaceous weeds have specific times of producing seed and it is important to reach them just before that time. So workers in a large reserve need to build up individual or group memory of what goes to seed when and where, and to visit critical areas at the crucial time. Mapping is thus of value and should be done after end of each season. A simple A4 map of the whole area � or a defined part of it � is convenient to use for recording and reporting purposes. Coordinates (latitude/longitude or northing/easting) may also be recorded, e.g. read from a map. A simple method is to sketch with pencil on a photocopy of a map (with contours). Circles or other appropriately shaped forms are placed on the affected areas, with diagonal lines for light-to-moderate infestation, or diagonal cross-hatching for heavy infestation. Even better than using a photocopy is to record the affected patches on a plasticized aerial photo, using coloured felt-pens. On such maps landmarks such as fences, trails or trees are easily visible. The maps can be photocopied and re-used each year. Baseline information. A preliminary mapping of weeds is also a valuable tool at the outset of any weed control programme. If a general mapping cannot be done, mapping of crucial particular weed species e.g. blackberry, Bathurst Burr etc., can be very useful. Monitoring. It is also valuable to document weed distribution and some estimate of density from year to year in order to measure progress. Towards an integrated approach. When weed infestation is very heavy in large areas of a reserve it may be difficult to adopt an integrated approach towards an area. The time of access to and from an area is a considerable factor in the time-effectiveness of weeding work. The more we can deal with all (or most of) the weeds in a given area at once, the better, from the aspect of economy of time. In practice it is difficult but not impossible to combine woody weed and herbaceous weed control. To do this effectively implies being able to carry around at least a mattock and small secateurs, a large bag for seedheads, and a spray-bottle loaded with glyphosate (or a weedbrush loaded with glyphosate) for woody weeds. A fully integrated approach of this sort will rarely be possible while weed infestations are heavy, but should be a goal towards which we may work gradually as weeds come under control year by year. We suggest that parkcare/landcare groups try, e.g.at the beginning of each annual cycle, to lay out a plan of weed control activities for both woody and herbaceous weeds for the year ahead. Probably the best time to do this is by about October. One problem to be addressed is that for many thistle infestations, action needs to be taken by November. The most crucial time for saffron and other thistles is in December/January when activities unfortunately often cease. Experience shows that with persistent effort, despite many problems and setbacks, it is usually possible to record progress each year and even spectacular progress, thanks to the amazing capacity of nature to take over when weed infestations are properly dealt with. It is hoped this website will contribute not only to correct management of individual weed-infestations, but also to formulation of effective plans for weed control in all parkcare/landcare groups. Towards a coordinated and systematic approach The ACT Pest Management Manual urges a systematic approach along these lines: Strategies: Defining priorities for weed control; coordination with other plans e.g. regional Identifying and recording extent of weed problems Defining resources available for weed control Creating awareness of weeds Preventing and minimizing spread Control measures and site rehabilitation Monitoring and evaluation of weed control programme Legislative support for wed control programme Developing an annual weed management plan. Mapping classifications: i) Broadscale mapping � 1=absent, 2=rare, 3=occasional, 4=common, 5=very common ii) Detailed mapping - Approximate % cover with each weed. Priorities can be established in a rational way by using the following criteria: Ease of control(of sites or weed species) Landform stability Conservation values for flora and fauna Recreation values Harmful characteristics of the weed(s) Invasiveness/reproductive potential. These criteria can be graded (1=low, 2=moderate, 3=high) and the scores summed for each particular weed or area considered to be controlled. Interim and long-term objectives are defined. This does not necessarily mean eradication of a weed or total control in an area � that may be impossible. The real aim is to reduce weed impact or potential impact to an acceptable level in a given area for all weeds or selected ones, sufficient at least to allow vigorous natural regeneration. Management options include: Eradication One-off control Sustained control Sporadic control No control. Usually a range of methods (manual, mechanical, herbicide, habitat improvement etc) will be needed for any one weed or area. The choice of method may depend on the target species, their habitat, presence of other species, physical access, resources available, time and other constraints, feasibility and cost of control. Implementation of the programme should be monitored regularly, and its impact periodically evaluated. Towards systematic weed control. This sort of approach is strongly recommended for parkcare/landcare groups that want to do more than just ad-hoc weed management. It is an objective of this Handbook to foster more motivation for and systematic work in weed control in the Canberra Region. Authors of the information on this website would be willing to work with parkcare/landcare groups to help define weed control priorities and plans. Particular points for the home gardener Some of the weeds dealt with in this website will be the same or similar for home gardens as for parkcare/landcare groups. Thistles: probably the commonest is the common sowthistle (milk thistle). The other large thistles � variegated, spear or Scotch � also occur. The important thing is to uproot them completely and remove seedheads completely. Grasses. In the home garden the main problem is usually the invasion of broadleaf weeds in the lawn. These may be effectively controlled by either carefully pulling out with the help of a weed fork, or by using a weedbrush containing a suitable herbicide. Using a spray-bottle is not advisable. Some grasses e.g. Kikuyu grass, couch � are very invasive. The lawn-edges need to be carefully and regularly trimmed. Other herbaceous weeds. Other weeds such as dock, oxalis, sticky weed (Galium aparine) tend to be more common. A common problem is that small weeds may spread from seed and rapidly establish themselves before they are noticed, and then it is difficult to extract them without damaging established flowering plants and shrubs. Areas where annuals recur should be noted down or marked, and watched carefully from springtime onwards so that action can be taken in time. Woody weeds. Many of the woody weeds listed in this website have entered nature reserves etc by direct spread of seeds/fruit from shrubs planted � often deliberately � in gardens as ornamentals; or through the consumption of seeds by birds who then transfer them elsewhere through droppings. One of the subsidiary hopes of this website is to raise awareness of the undesirable spread of woody weeds from gardens to conservation areas. In an effort to encourage home gardeners to substitute other plants for these �bush invaders� in their gardens, the Australian Native Plants Society (formerly known as Society for Growing Australian Plants) has arranged with several garden centre nurseries for a native plant suitable for gardens to be offered in exchange to any Canberra gardener who brings to the green-waste tip one of the noxious bush-invaders mentioned here. Volunteers of CNP/CUPP would also be willing to advise home gardeners on weed pests they may (unknowingly) have in their gardens, and help them to eliminate them. For advice on indigenous plants suitable to replace exotics as ornamentals in your garden contact The local parkcare group, or Canberra Nature Park coordinator, 6207 2193 The local landcare group or Canberra Urban Parks & Places, 6207 2500 Conservation Council of the South East Region and Canberra (Inc), 6236 9158 Australian Native Plants Society, 6251 1501. Go to Top of Page |