Discussion Paper - Part A - Victorian Environmental Assessment ...

Figure 5.22 Koala in a river red gum on Ulupna Island in Barmah State Park.A survey of Victorian parks in 1996 estimated thathorehound infested 78,200 ha of public land, cost$19,000 to control and took 1900 work-hours per year(Weiss et al. 2000). Treatment techniques for horehoundinclude the biological control agents horehound plumemoth and clearwing moth.Bathurst burr, introduced from tropical America, isprevalent in northern Victoria. It is an erect, branchedherb commonly growing from 30 to 60 cm tall and, likehorehound, its fruits are burrs. Bathurst burr is rarelygrazed due to its long spines and poisonous seeds andseedlings. It invades grassy woodlands, wetlands andriparian vegetation and forms dense patches capable ofexcluding other plant species. Bathurst burr can becontrolled using herbicides but control programs mustextend for more than six years to exhaust the seed bank.St John’s wort is a perennial herb around 80 cm highwith bright yellow flowers between October andJanuary. It was first introduced to the Ovens Valley in thelate 19th Century. It invades grasslands, woodlands,pastures, open forests, plantations, road and rail sidesand riverbanks. St John’s wort seeds can be spread bywind, animals, machinery, contaminated fodder, seed orsoil, and in garden waste. Biological control agents(beetles and mites) have been partly successful incontrolling this weed. There are two indigenous speciesof Hypericum that may co-occur with St John’s wort(Blood & CRC Weed Management Systems 2001).There are hundreds of weed species in the study area inaddition to these common species. Less obvious speciessuch as introduced fungi and plant rusts (e.g. Eucalyptusrust) could have significant impacts in the future.Vertebrate pests such as cats, foxes and rabbits are amajor problem in some areas. Their control consumeslarge parts of land management budgets. Feral pigs arealso pests on the floodplains of the Murray. Other feralvertebrates in the study area include brumbies, goats,feral cattle and wild dogs. Eight species of introducedfish are present in the rivers and streams of the studyarea. Negative effects on river health and biodiversity areknown for carp, rainbow and brown trout and mosquitofish.Foxes have a varied diet. They prey on native species,particularly those weighing between 35g and 5500g(Burbidge & McKenzie 1989). Foxes also consumeinvertebrates and plant material, and are vectors forsome weeds. The most common form of control is viathe use of 1080 (‘ten eighty’) poison baits placed in baitstations. Recent work suggests that large areas ofcontinuous baiting are required for baiting to reduce foxnumbers (DSE 2006h). Baiting programs are integratedwith Good Neighbour programs, which aim to reducepests on the adjoining private land and on public/privateland interfaces. In this circumstance, baiting is typicallytimed to protect newborn lambs.Rabbits are a major problem in much of the study area.Myxamotisis and Rabbit Haemorrhagic Disease (RHD)have reduced populations in some areas. However,history suggests that diseases only offer short-termrespite and that ongoing vigilance and control usingestablished techniques is vital, especially while theeffects of RHD are apparent. The Mallee Rabbits Projectaims to reduce rabbit populations on public land suchas Hattah-Kulkyne and Mulcra Island.80 River Red Gum Forests Investigation 2006