Hostname: page-component-586b7cd67f-r5fsc Total loading time: 0 Render date: 2024-11-22T18:09:05.710Z Has data issue: false hasContentIssue false
  • English
  • Français

Grazing Animals as Weed Control Agents

Published online by Cambridge University Press:  12 June 2017

Ian Popay  and
Roger Field
Ian Popay
Affiliation:
AgResearch Corporate Office, Private Bag 1135, Hamilton, New Zealand
Roger Field
Affiliation:
Plant Sci. Dep., Lincoln Univ., Lincoln, Canterbury, New Zealand
Get access Rights & Permissions [Opens in a new window]

Abstract

Literature on the effectiveness of grazing animals (especially cattle, goats, and sheep) in controlling weeds is reviewed. Availability of animals and the ability to fence them onto or off weed infestations are essential. Weeds of pastures are the most suitable subjects for control, although weeds of arable crops, forestry, and waste places are sometimes amenable to control by grazing animals. Although grazing animals themselves often cause weed problems in pasture, adjusting grazing timing or intensity or both can sometimes redress the balance. Increasing sheep or cattle stocking rates prevents animals from grazing selectively and can help control some weeds. Adjusting grazing pressure can also improve the growth of desirable pasture species so that these are more competitive and able to resist invasion of annual or biennial weeds. Introducing a different class of stock, like sheep into a cattle system or goats into a sheep system can control many weeds. Goats are capable of browsing on and controlling spiny or poisonous brush weeds, including gorse and poison ivy, without suffering adverse effects. Examples are given of the use of grazing animals for weed control in crops and forestry.

Keywords

Gorse, Ulex europaeus L. #3 ULEEUcattle, Bos tauntsgoats, Capra hircussheep, Ovis ariesNon-chemical weed controlintegrated weed managementlow input sustainable agricultureAgropyron cristatumAllium sativumAlnus rubraCarduus nutansC. pycnocephalusC. tenuiflorusCarthamus lanatusthistlesT. vermixTrifolium repensT. subterraneumZea maysCARLACENSOCIRARCIRPACIRVUCRUNUCRUPYCYPROECHPLEPHESHORLEHORMCHORMULOLRISTDTRSENJASILMATOXDITOXVX
Type
Review
Information
Weed Technology , Volume 10 , Issue 1 , March 1996 , pp. 217 - 231
Copyright
Copyright © 1996 by the Weed Science Society of America 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Literature Cited

1. Amor, R. L. 1972. Ecology of blackberry in Victoria. Verm. & Nox. Weeds Destr. Board, Victoria, pamphlet No. 35. p. 1–4.Google Scholar
2. Amor, R. L. 1987. Non-chemical weed control in Victorian dryland crops—the dream and the reality. Proc. Aust. Weeds Conf. 8:24–26.Google Scholar
3. Auld, B. A., Menz, K. M., and Tisdall, C. A. 1987. Weed Control Economics. Academic Press, London. 177 p.Google Scholar
4. Batten, G. J. 1979. Controlling scrub weeds with goats. New Zealand Weed and Pest Control Soc. 32:292–296.Google Scholar
5. Bendall, G. M. 1973. The control of slender thistle, Carduus pycnocephalus L. and C. tenuiflorus Curt. (Compositae), in pasture by grazing management. Aust. J. Agric. Res. 24:831–837.Google Scholar
6. Bentley, R. E. 1990. Managing grass weeds in a rotational cropping system. Proc. 9th Aust. Weeds Conf.: 243–245.Google Scholar
7. Betteridge, K., Costall, D. A., Hutching, S. M., Devantier, B. P., and Liu, Y. 1994. Ragwort (Senecio jacobaea) control by sheep in a hill country bull beef system. Proc. New Zealand Plant Prot. Conf. 47:53–57.Google Scholar
8. Breach, T. 1988. Bracken fern control with livestock: Te Wera Forest. For. Res. Inst. Bull. 139:76–84.Google Scholar
9. Cameron, E. 1935. A study of the natural control of ragwort (Senecio jacobaea L.). J. Ecol. 23:265–321.Google Scholar
10. Campbell, M. H., Hoist, P. J., Auld, B. A., and Medd, R. W. 1979. Control of three pasture weeds using goats. Proc. Asian-Pacific Weed Sci. Soc. 7:201–205.Google Scholar
11. Campbell, M. H. and Hoist, P. J. 1987. Control of Illyrian thistle, Onopordum illyricum, by goats. Proc. Aust. Weeds Conf. 8:24–26.Google Scholar
12. Campbell, R.J., Robards, G. E., and Saville, D. G. (1972) The effect of grass seed on sheep production. Proc. Aust. Soc. Anim. Prod. 9:225–229.Google Scholar
13. Carter, E. D. 1990. The role of grazing animals in weed control. Proc. Aust. Weeds Conf. 9:239–242.Google Scholar
14. Clark, D. A., Lambert, M. G., Rolston, M. P., and Dymock, N. 1982. Diet selection by goats and sheep on hill country. Proc. New Zealand Soc. Anim. Prod. 42:155–157.Google Scholar
15. Cossens, G. G., Mitchell, R. B., and Crossan, G. S. 1989. Matagouri, hawkweed and purple fuzzweed control with sheep, goats and legumes in the New Zealand tussock grassland. Proc. Brighton Crop Prot. Conf., Weeds. p. 879–884.Google Scholar
16. Cox, J. E., Taylor, R. H., and Mason, R. 1967. Motunau Island, Canterbury, New Zealand. An ecological survey. New Zealand DSIR Bull. 178.Google Scholar
17. Cousens, R. 1987. Theory and reality of weed control thresholds. Plant Prot. Q. 2:13–20.Google Scholar
18. Crouchley, G. 1983. Blackberry control in Hawkes Bay. Proc. Ruakura Farmers Conf. 35:63–65.Google Scholar
19. Dale, R. W. and Todd, A. C. 1988. Using cattle to control pampas grass in Maramarua and Waiuku Forests. New Zealand For. Res. Inst. Bull. 139:95–103.Google Scholar
20. Dellow, J. J., Mitchell, T., Johnston, W., Hennessey, G., and Gray, P. 1987, Large area blackberry, Rubus fruticosus agg., control using grazing goats. Proc. Aust. Weeds Conf. 8:70.Google Scholar
21. Dellow, J. J. and McDonald, W. 1990. Weed control in lucerne and pasture 1990. New South Wales Agric. and Fish. Agdex 130/640.Google Scholar
22. Desrochers, A. M., Bain, J. F., and Warwick, S. I. 1988. The biology of Canadian weeds. 89. Carduus nutans L. and Carduus acanthoides L. Can. J. Plant Sci. 68:1053–1068.Google Scholar
23. Eadie, I. M. and Robinson, B. D. 1953. Control of ragwort by hormone type herbicides. J. Aust. Inst. Agric. Sci. 19:192–196.Google Scholar
24. Edmonds, D. K. and Popay, A. I. 1983. Effect of pasture competition on the survival and flowering of nodding thistle. Proc. New Zealand Weed Pest Control Conf. 36:89–92.Google Scholar
25. Evans, I. A. and Mason, J. 1965. Carcinogenic activity of bracken. Nature, London. 205:913–914.Google Scholar
26. Fay, P. K., McElligott, V. T., and Havstad, K. M. 1989. Containment of free-ranging goats using pulsed-radio-wave-activated shock collars. Appl. Anim. Behav. Sci. 23:165–171.Google Scholar
27. Ferris-Kaan, R. 1992. Grazing as a management tool in woodland. Report of a meeting of the Forest Ecology Group held in the Lake District 16–17 Sept. 1991. Bull. Br. Ecol. Soc. 23(1): 33–36.Google Scholar
28. Forbes, J. C. 1977. Population flux and mortality in a ragwort (Senecio jacobaea L.) infestation. Weed Res. 17:387–391.Google Scholar
29. George, J. M. 1972. Effects of grazing by sheep on barley grass (Hordeum leporinum Link) infestation of pastures. Proc. Aust. Soc. Anim. Prod. 9:221–224.Google Scholar
30. Green, D. R. 1989. Rangeland restoration projects in western New South Wales. Aust. Rangel. J. 11:2, 110–116.CrossRefGoogle Scholar
31. Gunning, B. A. 1966. Grazing management for control of barley grass. Proceedings New Zealand Weed Pest Control Soc. 19:127–130.Google Scholar
32. Hammerton, J. L. 1968. Nutgrass in Panama: first impression. Pest Articles and News Summaries (C) (PANS) 14:339–345.Google Scholar
33. Hansen, J. A. 1988. Experience in the use of livestock to control gorse in Ashley Forest. For. Res. Inst. Bull. 139:85–94.Google Scholar
34. Harper, J. L. 1958. The ecology of ragwort (Senecio jacobaea) with especial reference to control. Herbicide Abstr. 28:151–157.Google Scholar
35. Harper, J. L. 1957. Biological Flora of the British Isles—Ranunculus acris L. (R. acer auct. plur.). J. Ecol. 45:289–342.Google Scholar
36. Harradine, A. R. 1987. Control of ragwort by Wiltshire Horn sheep. Proc. Aust. Weeds Conf. 8:64.Google Scholar
37. Harradine, A. R. and Jones, A. L. 1985. Control of gorse regrowth by Angora goats in the Tasmanian Midlands. Aust. J. Exp. Agric. 25:550–556.CrossRefGoogle Scholar
38. Hartley, M.J. 1981. The effect of grazing and pasture species on the survival of Scotch thistle. Proc. New Zealand Weed Pest Control Soc. 34:114–116.Google Scholar
39. Hartley, M. J. 1983. Effect of rushes on sheep carrying capacity. Proc. New Zealand Weed Pest Control Soc. 36:83–85.Google Scholar
40. Hartley, M. J., Atkinson, G. C., Bimler, K. H., James, T. K., and Popay, A. I. 1978. Control of barley grass by grazing management. Proc. New Zealand Weed Pest Control Soc. 31:198–202.Google Scholar
41. Hartley, M. J. and Bimler, K. H. 1975. Barley grass damage to lambs. Proc. New Zealand Weed Pest Control Soc. 31:2–6 Google Scholar
42. Hartley, M. J., Lyttle, L. A., and Popay, A. I. 1984. Control of Californian thistle by grazing management. Proc. New Zealand Weed Pest Control Conf. 37:24–27.Google Scholar
43. Hartley, M. J. and Hong Thai, Phung 1982. Effects of pasture species, fertilizer and grazing management on the survival of gorse seedlings. New Zealand J. Exp. Agric. 10:193–196.Google Scholar
44. Hartley, M. J. and Thomson, N. A. 1981. Effect and control of Californian thistle in dairy pasture. Proc. New Zealand Grassl. Assoc. 43:104–107.Google Scholar
45. Holgate, G. L. and Weir, D. A. 1987. Sweet brier control with goats. Proc. New Zealand Grassl. Assoc. 48:157–161.Google Scholar
46. Holmes, R. 1994. A natural way with weeds. New Scientist 142 (1924) 22–23.Google Scholar
47. Hoist, P. J. and Campbell, M. H. 1987. The role of goats in the control of weeds of pastures. p. 262–263 in Wheeler, J. L., Pearson, C. J., Robards, G. E. Temperate Pastures. Aust. Wool Corp./CSIRO.Google Scholar
48. Howe, J. C. Barry, T.N., and Popay, A. I. 1988. Voluntary intake and digestion of gorse (Ulex europaeus) by goats and sheep. J. Agric. Sci., Cambridge 111:107–114.Google Scholar
49. Huntsinger, L. 1990. Grazing in California's mixed conifer forests: Studies in the central Sierra Nevada. Dissert. Abstr. Int. B, Sci. and Eng. 50:10, 4314B.Google Scholar
50. Jen, I. A., Chen, Y. H., and Chen, K.J.E. 1987. Economic feasibility of forest range in Taiwan. Bull. Taiwan For. Res. Inst. 2:211–215.Google Scholar
51. Johnston, A. and Peake, R. W. 1960. Effect of selective grazing by sheep on the control of leafy spurge (Euphorbia esula L.). J. Range Manage. 13:192–195.Google Scholar
52. Jones, J. R. and Merchant, M. 1991. A possible biological method of controlling rushes in grassland using goats. p. 10.5–10.6 in Strategies for weed, disease and pest control in grassland. Proc. Br. Grassl. Soc. Conf.Google Scholar
53. Julien, M. H. 1982. Biological Control of Weeds. A World Catalogue of Agents and their Target Weeds. Commonwealth Agricultural Bureaux, Slough, UK.Google Scholar
54. Kok, L. T., Mc Avoy, T. J., and Mays, W. T. 1986. Impact of tall fescue grass and Carduus thistle weevils on the growth and development of musk thistle (Carduus nutans). Weed Sci. 34:966–971.Google Scholar
55. Lacey, J., Wallander, R., and Olson-Rutz, K. 1992. Recovery, germinability, and viability of leafy spurge (Euphorbia esula) seeds ingested by sheep and goats. Weed Technol. 6:599–602.Google Scholar
56. Landgraf, B. K., Fay, P. K., and Havstad, K. M. 1984. Utilization of leafy spurge (Euphorbia esula) by sheep. Weed Sci. 32:348–352.Google Scholar
57. Leininger, W. C. and Sharrow, S. H. 1989. Seasonal browsing of Douglas fir seedlings by sheep. West. J. App. For. 4:73–76.Google Scholar
58. Liebman, M. and Janke, R. R. 1990. Sustainable weed management practices. p. 111–143 in Francis, C. A., Flora, C. B., King, L. D. Sustainable Agriculture in Temperate Zones. John Wiley and Sons, New York.Google Scholar
59. Ludecke, T. E. and Molloy, B.P.J. 1968. The improvement, utilisation and production of low altitude tussock country in Otago. Proc. New Zealand Grassl. Assoc. 28:46–58.Google Scholar
60. Lym, R. G. and Kirby, D. R. 1987. Cattle foraging behaviour in leafy spurge (Euphorbia esula)-infested rangeland. Weed Technol. 1:314–318.Google Scholar
61. McDonald, P. M. and Fiddler, G. O. 1991. Vegetation management in young conifer plantations in California. Proc. 44th Annu. Meet. South. Weed Sci. Soc. 257–264.Google Scholar
62. MacGregor, B. A., Reid, C. J., and Scott, B. J. 1990. The effect of goats and sheep on the growth, flowering and longevity of tall, medium and short Scotch and artichoke thistles. Proc. Aust. Weeds Conf. 9:497–500.Google Scholar
63. McKinnon, D. 1982. Angoras clobber sweet brier. New Zealand Farmer, Sept. 23, 1982, p. 17–22.Google Scholar
64. McLeod, E. J. and Swezey, S. L. 1980. Survey of weed problems and management technologies. Res. leaflet, Univ. of Cal. Appr. Tech. Prog., Davis. Cited in Liebman and Janke (1990).Google Scholar
65. Martin, R. J. and Knight, T. L. 1987. Effect of date of defoliation on yield of autumn barley sown on different dates. Proc. Agron. Soc. New Zealand. 17:85–89.Google Scholar
66. Matthews, L. J. 1975. Weed control by chemical methods. Government Printer. Wellington, New Zealand.Google Scholar
67. Mayton, E. L., Smith, E. V., and King, D. 1945. Nutgrass eradication studies: IV. Use of chickens and geese in the control of nutgrass (Cyperus rotundus L.). J. Am. Soc. Agron. 47:785–791.Google Scholar
68. Mitchell, R. B. and Abernethy, R. J., 1993. Integrated management of Californian thistle in pasture. Proc. New Zealand Weed Pest Control Conf. 46:278–281.Google Scholar
69. Moog, F. A. 1993. Sustainability of forage-livestock production in smallholder and plantation systems of Asia. Proc. Int. Grassl. Cong. 17:493–496.Google Scholar
70. Morley, F.H.W., Bennett, D., and McKinney, G. T. 1969. The effect of intensity of rotational grazing with breeding ewes of phalaris-subterranean clover pastures. Aust. J. Exp. Agric. Anim. Hush. 9:74–84.Google Scholar
71. Mortimer, P. H. and White, E. P. 1975. Toxicity of some composite (Senecio) weeds. Proc. New Zealand Weed Pest Control Conf. 28:88–91.Google Scholar
72. Moss, G.R. 1959. The gorse seed problem. Proc. New Zealand Weed Conf. 12:59–64.Google Scholar
73. Myers, L. F. and Squires, V. R. 1970. Control of barley grass (Hordeum leporinum) by grazing management in irrigated pastures. Aust. J. Exp. Agric. Anim. Husb. 10:151–155.Google Scholar
74. Nambiar, G. 1991. Cattle rearing under oil palm. Planter 67:598–605.Google Scholar
75. National Research Council. 1989. Alternative Agriculture. Nat. Acad. Sci., Washington D.C. Google Scholar
76. Okigbo, B. N. and Sabiiti, E. N. 1993. Sustainability of African farming systems with particular reference to soil fertility, multiple cropping systems and weed ingress in smallholder systems in humid tropical Africa. Proc. Int. Grassl. Cong. 17:473–492.Google Scholar
77. Panetta, F. D. and Wardle, D. A. (1992) Gap size and regeneration in a New Zealand dairy pasture. Aust. J. Ecol. 17:169–175.Google Scholar
78. Paul, J. S. 1993. Goals control poison ivy, oak and sumac. Small Farm Today. June 1993:44.Google Scholar
79. Phung, H. T. and Popay, A. I. 1981. Effect of pasture cover on the germination of certain weed seeds. Proc. New Zealand Weed Pest Control Conf. 34:111–113.Google Scholar
80. Pierce, J. R. 1987. The use of goals for control of saffron thistle, Carthamus lanatus L. Proc. Aust. Weeds Conf. 8:31–34.Google Scholar
81. Pierce, J. 1991. Using goals to control weeds. J. Agric. West. Aust. 32:83–87.Google Scholar
82. Pineiro-Andion, J. and Perez-Fernandez, M. P. 1988. Production of pastures between pines—a solution to reduce the risk of forest fires. Agric. Madrid 672:480–484.Google Scholar
83. Poole, A. L., and Cairns, D. 1940. Botanical aspects of ragwort (Senecio jacobaea L.) control. New Zealand D.S.I.R. Bull. 82.Google Scholar
84. Popay, A. I. 1975. Laboratory germination and seedling emergence of barley grass. Proc. New Zealand Weed Pest Control Conf. 28:7–11.Google Scholar
85. Popay, A. I. and Field, R. J. 1992. Grazing animals as biological control agents. Proc. First Int. Weed Control Cong. 273–277.Google Scholar
86. Popay, A.I., Hartley, M. J., and Crouchley, G. 1981. The effect of different pasture cultivars on barley grass invasion. Proc. New Zealand Weed and Pest Control Conf. 34:107–111.Google Scholar
87. Popay, A. I. and Medd, R. W. 1990 The biology of Australian Weeds. 21. Carduus nutans L. ssp. nutans . Plant Prot. Q. 5:3–13.Google Scholar
88. Popay, A.I. and Sanders, P. 1975. Effect of depth of burial on seed germination and seedling emergence of barley grass (Hordeum murinum L.). New Zealand J. Exp. Agric. 3:77–80.Google Scholar
89. Popay, A.I. and Sanders, P. 1982. Effect of pasture competition on barley grass seed production. New Zealand J. Agric. Res. 25:143–146.Google Scholar
90. Powle, S. B. and Hokum, J.A.M. 1990. Herbicide resistant weeds in Australia. Proc. Aust. Weeds Conf. 8:185–193.Google Scholar
91. Radcliffe, J.E. 1982. Gorse control with sheep and goats. Proc. New Zealand Weed Pest Control Conf. 35:130–134.Google Scholar
92. Radcliffe, J. E. 1983. Gorse control in Canterbury. Proc. Ruakura Farmers Conf. 35:59–61.Google Scholar
93. Radcliffe, J. E. 1986. Gorse—a resource for goats? New Zealand J. Exp. Agric. 14:399–410.Google Scholar
94. Ralphs, M. H., Bowns, J. E., and Manners, G. D. 1991. Utilization of larkspur by sheep. J. Range Manage. 44:619–622.Google Scholar
95. Ralphs, M. H. and Olsen, J. D. 1992. Prior grazing by sheep reduces waxy larkspur consumption by cattle. J. Range Manage. 45:136–139.Google Scholar
96. Reid, R. L. (1981). A manual of Australian Agriculture, 4th ed. Heinemann, Melbourne.Google Scholar
97. Riveros, F. 1993. Grasslands for our world. Proc. Int. Grassl. Cong. 17:15–20.Google Scholar
98. Rolston, M. P., Lambert, M. G., Clark, D. A., and Devantier, B. P. 1981. Control of rushes and thistles in pasture by goat and sheep grazing. Proc. New Zealand Weed Pest Control Conf. 34:117–121.Google Scholar
99. Rolston, M. P., Lambert, M. G., and Clark, D. A. 1982. Weed control options in hill country. Proc. New Zealand Grassl. Assoc. 43:196–203.Google Scholar
100. Rolston, M. P. and Talbot, J. 1980. Soil temperatures and regrowth of gorse burnt after treatment with herbicides. New Zealand J. Exp. Agric. 8:55–61.Google Scholar
101. Rosenthal, S. R., Maddox, D. M., and Brunetti, K. 1985. Biological Control Methods. p. 65–94, in Principles of Weed Control in California (California Weed Conference). Thomson Publications, Fresno, CA.Google Scholar
102. Rumball, P. J. 1970. Costs of barley grass. Proc. New Zealand Weed Pest Control Conf. 23:77–82.Google Scholar
103. Saxby, S. H. 1935. Ecological aspects of weed control in pastures. Proc. 3rd New Zealand Weeds Conf. 51–55.Google Scholar
104. Sharrow, S. H., Leininger, W. C., and Osman, K.A.T.I. 1992. Sheep grazing effects on coastal Douglas fir forest growth: a ten-year perspective. For. Ecol. Manage. 50:75–84.Google Scholar
105. Sharrow, S. H. and Mosher, W. D. 1982. Sheep as a biological control agent for tansy ragwort. J. Range. Manage. 35:480–482.Google Scholar
106. Shugg, A. W. and Vivian, G. W. 1973. Barley grass: its effects on value of sheep products. Proc. New Zealand Weed Pest Control Conf. 26:82–86.CrossRefGoogle Scholar
107. Smith, D. F. 1968a. The growth of barley grass (Hordeum leporinum) in annual pasture. I. Germination and establishment in comparison with other annual pasture species. Aust. J. Exp. Agric. Anim. Husb. 8:478–483.Google Scholar
108. Smith, D. F. 1968b. The growth of barley grass (Hordeum leporinum) in annual pasture. 4. The effect of some management practices on barley grass content. Aust. J. Exp. Agric. Anim. Husb. 8:706–711.Google Scholar
109. Somarriba, E., Lega, F., and Somarriba, E. J. 1991. Cattle grazing under Pinus caribaea. 1. Evaluation of farm historical data on stand age and animal stocking rate. Agroforestry-Systems. 13:177–185.Google Scholar
110. Squibb, R. C., Provenza, F. D., and Balph, D. F. 1990. Effect of age of exposure on consumption of a shrub by sheep. J. Anim. Sci. 68:987–997.Google Scholar
111. Taylor, J. A. 1990. Towards an integrated bracken control technology. p. 40–46 in Bassett, C., Whitehouse, L. J., Zabkiewicz, L. J. J. A., eds. Alternatives to the chemical control of weeds. Ministry of Forestry. For. Res. Inst. Bull. 155. Rotorua, New Zealand.Google Scholar
112. Taylor, R. L. 1971. Fence sheep off barley grass. Proc. New Zealand Weed Pest Control Conf. 24:74.Google Scholar
113. Thomas, A. J., Watkin, J. E., Evans, I. A., and Evans, W. C. 1955. The bracken poisoning of ruminants. Biochem. J. 61:viii,Google Scholar
114. Thomsen, C. D., Williams, W. A., George, M. R., McHenry, B., Bell, F. L., and Knight, R. S. 1989. Managing yellow starthistle on rangeland. California Agric. 43:4–7.Google Scholar
115. Thomsen, C. D., Williams, W. A., Vayssiére, M., Bell, F. L., and George, M. R. 1993. Controlled grazing on annual grassland decreases yellow starthistle. California Agric. 47:36–40.Google Scholar
116. Thomson, N. A. and Power, M. T. 1993. An evaluation of a possible complementary effect of grazing goats with bulls in an intensive bull beef system. New Zealand Soc. Anim. Prod. 53:23–27.Google Scholar
117. Thompson, A. and Saunders, A. E. 1986. The effect of fertilizer on ragwort in pasture. Proc. New Zealand Weed Pest Control Conf. 39:175–178.Google Scholar
118. Thompson, A., Saunders, A. E., and Martin, P. 1987. The effect of nodding thistle (Carduus nutans) on pasture production. Proc. New Zealand Weed Pest Control Conf. 40:222–225.Google Scholar
119. Tuckett, A.J. 1961. Giant buttercup. Proc. New Zealand Weed Control Conf. 14:124–126.Google Scholar
120. van Zon, J.C.J. 1978. Status of biotic agents, other than insects or pathogens, as biocontrols. Proc. Int. Symp. Biol, Control of Weeds 4:245–250.Google Scholar
121. Walker, B. H. 1993. Stability in rangelands: ecology and economics. Proc. Int. Grassl. Cong. 17:1885–1890.Google Scholar
122. Walker, J. W., Hemenway, K. G., Hatfield, P. G., and Glimp, H. A. 1992. Training lambs to be weed eaters: Studies with leafy spurge. J. Range Manage. 45:245–249.Google Scholar
123. Wardle, D. A., Ahmed, M., and Nicholson, K. S. 1991. Allelopathic influence of nodding thistle (Carduus nutans L.) seeds on germination and radicle growth of pasture plants. New Zealand J. Agric. Res. 34:185–191.Google Scholar
124. Wardle, D. A., Nicholson, K. S., and Rahman, A. 1993. Influence of plant age on the allelopathic potential of nodding thistle (Carduus nutans L.) against pasture grasses and legumes. Weed Res. 33:69–78.Google Scholar
125. Wardle, D. A., Nicholson, K. S., Ahmed, M., and Rahman, A. 1994. Interference effects of the invasive plant Carduus nutans L. against the nitrogen fixation ability of Trifolium repens L. Plant Soil 163:287–297 Google Scholar
126. Warr, G. J. and Thompson, J. M. 1976. Liveweight change and intake of lambs as affected by seed infestation. Aust. Soc. Anim. Prod. 11:173–176.Google Scholar
127. West, G. G. and Dean, M. G. 1990. The use of livestock to control weeds in New Zealand forests. p. 128–132 in Bassett, C., Whitehouse, L. J., Zabkiewicz, J. A., eds. Alternatives to the chemical control of weeds. Ministry of Forestry, For. Res. Inst. Bull. 155, Rotorua, New Zealand.Google Scholar
128. Wood, G. M. 1987. Animals for biological brush control. Agron. J. 79:319–321.CrossRefGoogle Scholar
129. Wright, R. 1927. Goats and noxious weeds control. New Zealand J. Agric. 35:295–297.Google Scholar
130. Zabkiewicz, J. A. and Gaskin, R. E. 1978. Effect of fire on gorse. Proc. New Zealand Weed and Pest Control Conf. 31:47–52.CrossRefGoogle Scholar