Bushland Weeds Manual - Environmental Weeds Action Network

More documents

Recommendations

Info

40 Chapter 4 Corms, Bulbs and Tubers Timing is everything Understanding the life-cycle of the weedy geophytes over the growing season can mean the difference between effective control and unwitting spread. For many species hand-removal should only be carried out early in the growing season. • Late in the growing season specialised roots (known as contractile roots) drag annually renewed corms or bulbs deeper down into the soil. For the relevant species hand-removal is much easier and causes a lot less soil disturbance if undertaken early in the growing season e.g. Freesia, Sparaxis and Watsonia. • Stem cormels and bulbils are produced towards the end of the growing season. These are easily dislodged and can contribute to the spread of the weed you are trying to control e.g. Freesia, Sparaxis bulbifera, Lachenalia bulbifera. • Oxalis species produce bulbils at the nodes of underground stems later in the season, just after flowering. These are easily dislodged and handremoval, after bulbil formation has occurred, will generally contribute to their spread e.g. Soursob, Finger Leaf Oxalis and Four O’Clock. • Towards the end of the growing season, as the days get longer and warmer, many species finish flowering and start producing seed (often coincides with bulbil and cormel production). When physically removing plants that are setting seed ensure seed is not dislodged and spread through the bushland as material is transported. For the following species physical removal is hazardous at any time. • Those species that produce masses of cormels around the base are extremely difficult to physically remove without dislodging and spreading cormels any time of the year. The cormels are tiny, float in water and easily stick with mud to boots, tools and the feet of animals. Physical removal needs to be undertaken in a way that avoids releasing or dropping cormels. e.g. Wavy Gladiolus, Long Tubed Painted Lady (Gladiolus angustus) and Two Leaf Cape Tulip. The parent corm often confers dormancy on cormels and its removal is often followed by mass germination of those cormels left behind. • Arum Lily produces numerous tiny daughter tubers that become dislodged during handremoval. This appears to happen throughout the growing season. • The rhizomes attached to the tubers of Bridal Creeper will produce new shoots from any tiny fragments left behind. Note: Physical removal of weeds such as Watsonia, Arum Lily or Bridal Creeper on steeper slopes or along creeks and riverbanks can lead to serious soil erosion. fruits containing seed stem cormels a b c d Harlequin flower (Sparaxis bulbifera); a) Summer, dormant corm b) Late autumn, corm begins to sprout c) Early spring, flowering and corm exhaustion d) Spring to early summer, leaves begin to die back, seed and stem cormels are formed.
Slashing leaves and stems Repeated removal of leaves and stems of some species of weedy geophytes over time can reduce population density, reproductive output and plant vigour. It is generally labour intensive, however, and often not effective in the longer term. The few examples below illustrate where it can be a useful tool, under certain circumstances. • If Bridal Creeper is slashed back to the stem bases every month over the growing season for several years plants are severely weakened (J. Moore pers. comm.). In bushland on Garden Island, just off the coast of Perth, continual grazing by Tammar wallabies has prevented Bridal Creeper from becoming wide-spread on the island (Keighery 1993). • Trials in the fringing vegetation along Bennett Brook in Perth suggested that slashing Arum Lily back to the base every month over the growing season can, in the short term at least, greatly reduce the number of adult plants in a population. Plants were slashed to the base every month for seven months over the 1999 growing season. Over 80 % of plants in the population did not resprout in the 2000 season (Brown unpubl). The slashing was done by hand with a sharp hoe and would be very labour intensive over a broad area. The work would need to continue over a number of years and if left for any length of time populations would probably quickly return to pre-treatment levels. • Work in South Australia has found if Bulbil Watsonia plants are slashed at 15 centimetres or less above the ground, at the first sign of a flower spike, neither flower spike nor bulbils will be produced in that year. In addition the plant will form smaller corms the following year (Wilson and Conran 1993). Note: simply removing flower spikes to prevent seed set can sometimes lead to more vigorous plants the following year. Work on Pink Gladiolus in south west Western Australia found that removal of flowers just as they were opening resulted in a larger replacement corm (and presumably more vigorous plants that would be harder to kill) the following year (Hocking 1992). Chemical control methods Chemical control of bulbous, cormous and tuberous weeds is often the only practical option available for dense infestations invading good bushland. It can be practical on a large scale, avoids soil disturbance and prevents soil erosion. Herbicide application needs to be done by experienced operators with the correct equipment, knowledge of herbicides and an understanding of bushland and of the native flora. Regardless of the herbicide, application needs to be carefully timed to be effective on many of the species dealt with in this chapter, particularly the annually renewed bulbs and corms (Box 4.4). Note: Anyone applying herbicides should have appropriate training in the safe use and handling of relevant chemicals (Chapter 8). Chapter 4 Corms, Bulbs and Tubers The herbicides Important note: The following herbicides are currently the subject of a minor use off-label permit in non-crop situations in Western Australia. Application must comply with all conditions of the permit. Available from: (http://permits.nra.gov.au/PER4984.PDF). Glyphosate When applied at the correct stage of the life-cycle, this non-selective herbicide has been found to be effective against a number of South African bulbous, cormous and tuberous species. These include Freesia (Freesia alba x leichtlinii), Ixia species (Dixon and Keighery 1995), Watsonia (Day 1993) and Bridal Creeper (Pritchard 2002). Glyphosate is an acceptable option where the weeds occur in dense monocultures on the disturbed edges of bushland. However these weeds often grow closely amongst native vegetation and the use of non-selective herbicides can lead to unacceptable off-target damage unless the application method is very carefully targeted (Box 4.2 and Box 4.3). Metsulfuron methyl Following the introduction of the sulfonylurea group of herbicides in early 1980s, metsulfuron methyl (Brushoff ® , Ally ® ) in particular has been found to be very effective against a number of South African bulbous/cormous species. These include Soursob (Peirce 1998), Bridal Creeper (Pritchard 1991, Dixon 1996), Freesia (Dixon 1998b), Harlequin Flower (Meney 1999, Brown and Brooks in press c) and Yellow Soldier (Brown et al. 2002). Interestingly, some of these studies suggest that many native species are resistant to the effects of metsulfuron methyl at rates of 5 g/ha and below (Dixon 1996, Meney 1999, Moore 1999, Brown et al. 2002, Brown and Brooks in press c). This is an area that requires further study and any use of the sulfonylurea group of herbicides in bushland needs very careful consideration. Metsulfuron methyl can remain active in dry alkaline soils and is absorbed by roots for many months following application (Parsons 1995, Noy 1996, Sarmah et al. 1998). Chlorsulfuron Also of the sulfonylurea group of herbicides, chlorsulfuron (Glean ® ) is known to be effective on Arum Lily (Moore and Hoskins 1997), Cape Tulip (Parsons and Cuthbertson 2001) and Harlequin Flower (Brown and Brooks 2002). The impacts of chlorsulfuron on native plants that co-occur with these weeds are not well understood. Trials on Harlequin Flower invading herb-rich shrublands in the Brixton Street Wetlands indicated chlorsulfuron had an impact on some native herbs (Brown and Brooks in press c). Important note: Both metsulfuron methyl and chlorsulfuron can inflict damage to vegetation at very low concentrations. Both can remain active in the soil for some months following application. They should only be spot sprayed on target species invading native bushland and always by well-qualified responsible operators with a thorough knowledge of the native flora. 2,2-DPA Reported to successfully control Watsonia invading remnant native vegetation. Sprayed at a rate of 10 g/L, 2,2-DPA has little impact on a range of native species (Moore and Fletcher 1994, Brown and Brooks unpubl.). 41
Page 1 and 2: Bushland Weeds A practical guide to
Page 3: Acknowledgments This manual is the
Page 6 and 7: iv Introduction The Banksia, Tuart
Page 8 and 9: 2 Chapter 1 The Project Blue Gum La
Page 10 and 11: 4 Chapter 1 The Project Both Arum L
Page 12 and 13: 6 Chapter 2 Managing Weeds in Bushl
Page 14 and 15: 8 Chapter 2 Managing Weeds in Bushl
Page 16 and 17: 10 Chapter 3 Grass Weeds Many grass
Page 18 and 19: 12 Chapter 3 Grass Weeds Box 3.3 Gr
Page 20 and 21: 14 Chapter 3 Grass Weeds • Transi
Page 22 and 23: 16 Chapter 3 Grass Weeds Control te
Page 24 and 25: 18 Chapter 3 Grass Weeds Rhizomatou
Page 26 and 27: 20 Chapter 3 Grass Weeds Case Studi
Page 34 and 35: Chapter 3 Grass Weeds Management Ta
Page 36 and 37: Chapter 3 Grass Weeds Management Ta
Page 38 and 39: 32 Chapter 4 Corms, Bulbs and Tuber
Page 58 and 59: Chapter 4 Corms, Bulbs and Tubers W
Page 60 and 61: Iridaceae Moraea miniata Two Leaf C
Page 62 and 63: Chapter 5 Broadleaf Herbs, Sedges a
Page 64 and 65: 58 Chapter 5 Broadleaf Herbs, Sedge
Page 72 and 73: Chapter 5 Annual Broadleaf Herbs, S
Page 74 and 75: Chapter 5 Annual Broadleaf Herbs, S
Page 76 and 77: Chapter 5 Perennial Broadleaf Herbs
Page 78 and 79: Chapter 5 Perennial Broadleaf Herbs
Page 80 and 81: 74 Chapter 6 Trees, Shrubs and Clim
Page 92 and 93: Chapter 6 Trees, Shrubs and Climber
Page 94 and 95: Chapter 6 Trees, Shrubs and Climber
Page 96 and 97:
90 Chapter 7 Weed Mapping in Remnan
Page 98 and 99:
92 Chapter 7 Weed Mapping in Remnan
Page 100 and 101:
94 Chapter 8 Herbicide Use in Bushl
Page 102 and 103:
Page 104 and 105:
Page 106 and 107:
100 Final Note In the end, environm
Page 108 and 109:
102 References 1 Aarssen, L.W., Hal
Page 110 and 111:
104 References 101 Dixon, B. (2002)
Page 112 and 113:
106 References 204 Mann, R. (1998)
Page 114:
108 307 The Nature Conservancy (200
show all

Bushland Weeds Manual - Environmental Weeds Action Network

Create successful ePaper yourself

Delete template?

Save as template?