Tilapia

Tilapia (Oreochromis mossambicus) is an invasive species native to Africa, Sri Lanka and southern India.  They are sometimes referred to the ‘rabbit’ of Queensland’s waterways. They directly compete with native species through their aggressive behaviour, for food and habitat space and are even known to eat native fish’s eggs!  They are mainly a freshwater fish and inhabit shallow streams, rivers, dams, ponds and lakes (Durack Institute of technology).   Many factors make them very successful and allow them to dominate over native fish. They are highly efficient breeders (including mouth brooding), their eggs have been known to last up to one month in dry conditions and adult fish have no natural enemies. Tilapia also has a strong resistance to disease and thrives in a warm environment. They have a preference for eating duckweed which can be problematic, which is why tilapia has been introduced in the past. This has also become a problem for other aquatic plants as they destroy root systems and dig up the ground (Durack Institute of technology).   Like many pests once they are established in the wild can be very hard to eradicate so prevention of spreading is best. To stop the spread of tilapia lies in public education.   IT is illegal to breed or buy or sell Tilapia in Queensland and heavy penalties apply.  Currently the Department of Primary Industries is trailing several eradication programs including drying and draining off in small water bodies such as farm dams. Another option is poisoning, however this is only under strict circumstances and certain criteria has to be met as to limit the impacts on native species (Australian Government, 2014).

Viewed 31.05.2014

 

References: Noxious Invasive Species Control, 2014, Durack, Institute of Technology.

 

http://www.durack.edu.au/research/current-projects/noxious-invasive-species-control-(tilapia)

 

Queensland Government, 2014, Department of Primary Industries.

Leucaena: Miracle plant or menace?

Leucaena leucocephala is a long-lived shrub native to Central and South America. It is a tropical plant and can tolerate a range of rainfall from 500-3500mm and withstands strongly seasonal (6 to 8 month) dry climates. Although it is an invasive species it has been introduced due to its beneficial qualities. Its major use being a nutritious forage tree for cattle and livestock, but other positive uses are providing firewood, timber, shade and erosion control. Also hedges can be useful as windbreaks and firebreaks (Shelton H.K, Brewbaker, JL, 2014)

 



Viewed 23.05.2014

Problems with Leucaena can arise when it is not heavily grazed or controlled as it can grow up to 8m and grows too tall for cattle to eat. It then can spread quite rapidly into water ways and creek lines as well as hinder movement of wildlife. It can form dense thickets which are reported to be replacing native forest in some areas threatening endemic species. These thickets can render some areas unusable and inaccessible.  It  is a declared weed in New Guinea, Hawaii, and western Polynesia and in the United States however it is not a declared plant in Qld under the land protection (pest stock route management) act 2002 (Department of Agriculture, fisheries and Forestry)

 

A study was conducted in Thailand on the role Leucaena played on tree regeneration in the Khao Phuluang Forest. The results suggested that the leucaena restricted the native forest by its invasive habit and reduces light transmittance to the forest floor (Marod D, et al, 2012).

 

My understanding is that as long as this shrub is grazed and kept under control and confined to one area it can be used to an advantage.

 

References:

 

Department of Agriculture, fisheries and forestry, Biosecurity Queensland, Feburary 2014.

Marod D, Duenkae U, Sungkaew S, Wachrinret C, Asanok L, Klomwattankul N, 2012, ‘The influences of an invasive species (Leucaena leucocephala) on tree regeneration in Khe Phulary Forest, Northeastern Thailand. Forest Biology, vol. 46, pp. 39-50

Shelton H.M, Brewbaker J.L, 2014

http://www.fao.org/ag/Agp/agpc/doc/Publicat/Gutt-shel/x5556e06.htm

Deer vs Forest

Deer were introduced to Australia and New Zealand in the 19^th century from Europe as game animals meaning they were brought over for recreational hunting. As the feral deer (family Cervidae) population increase they are invading new areas causing damage to both the natural environment and agriculture business. As herbivores they destroy native vegetation by trampling plants, grazing and ring-barking young trees, this causes damaging changes in plant communities, such as modifications in nutrient cycling. Deer also cause dramatic changes to the understory composition and structure of some forests.  Through their foraging selectivity they also contribute to the spread of weeds and potentially transmit diseases (Coomes D.A, etal, 2003).

The spread of deer populations have been a result of escapes or releases from deer farms. The most effective step to managing the impacts of deer is to prevent more deer from entering the wild. Control programs are best carried out as a joint exercise involving all land managers in the district. These methods include shooting either via helicopter or ground shooting, recreational shooting, trapping and fencing.

During a recent study to restore ecosystems that are affected by the invasive deer it was discovered that after the eradication of the pest it was difficult to reverse the effects. However the long term affects of the ecosystem responses is hard to determine as deer control has not been imposed in many places for a length of time that it is possible to note generations of long-lived plant species (Tanentzap A.J, etal, 2009).

 

References:

Coomes D.A, Allen, R.B, Forsyth D.M, Lee W.G, 2003, ‘Factors preventing the recovery of New Zealand Forests following Control of invasive deer’ Conservation Biology, vol.17, no.2, pp. 450-459

 

Tanentzap A.J, Burrows L.E, Lee W.G, Nugent G, Maxwell J.M, Coomes D.A, 2009, ‘Landscape-level vegetation recovery from herbivory: progress after four decades of invasive red deer control, Journal of Applied Ecology, vol.46, no.5, pp. 1064-1072.  

Mullumbimby Couch

While precipitation is essential for healthy lawns, gardens and pastures it also makes these areas susceptible to a troublesome weed known as Mullumbimby couch (Cyperus brevifolus). This plant is a sedge grass which flourishes in damp, acid soil conditions. It is described as a grass like plant with shiny leaves, triangular stems and globular seed heads.  It is a problem because it can rob the lawn of nutrients and water and if not treated will eventually take over.   The weed is currently distributed in all states of Australia expect Tasmania, particularly the northern and eastern areas. They are sneaky invaders because their fine foliage makes it difficult to detect until they are well established.  Being prolific seed producers they spread quickly to other areas using underground rhizomes (creeping stems).   Many lawn weeds are season problems, but the Cyperus species are perennial flowering from November to April. To control a small invasion hand weeding or spot-painting with certain herbicides can halt further spread. Because the plant spreads via their tubers in the soil most herbicides are inefficient as they attack only the visible parts of the weed. One product that is known to attack the entire plant is Sempra, it is selective to Mullumbimby and won’t harm the surrounding grass (Government of Western Australia, 2014).

 

References: Department of Agriculture and food, 2014, Government of Western Australia, viewed 05.07.2014

< https://www.agric.wa.gov.au/control-methods/lawn-problems?page=0%2C3>

The Asian House Gecko, Friend or Foe?

Since the establishment of the Asian house gecko, Hemidactylus frenatus,  in Australia 50 years ago there has been discussion regarding the potential impacts of this invasive species.  Australia is a centre of gecko origin and diversity so there is concern to what degree the Hemidactylus frenatus poses a threat Australia’s diversity and ecology. 

Some have argued that because Hemidactylus frenatus spread rapidly they can invade in natural habitats and are a strong competitor and may out-compete Australian geckos (Hoskin, 2010)

However a recent study has concluded that where they do invade it is in association with humanity, areas with lights and buildings; in human modified habitats and has no significant invasion into bush land where the Australian native geckos occupy habitats (Vanderduys E.P, Kutt A.S, 2013).

During a study conducted between 1997 and 2012 on the effects of fire, grazing and weeds on native reptiles across Queensland and the northern territory over 11 000 geckos were recorded, only 13 of which were Asian House geckos, and all from the same site in a Cape York community near homes. A site just 1km from the community was monitored recording no Asian house geckos.  This  revealed that while the invaders were found to be abundant in the community for over 30 years they had not managed to spread a kilometer.  From this evidence it has been concluded that the Asian house gecko were unlikely to become an environmental pest and aren’t likely to spread beyond areas of human influence (Vanderduys E.P, Kutt A.S, 2013).

 

Referenences:

Hoskin, C.J 2010, ‘The Invasion and Potential Impact of the Asian House Gecko (Hemidartylus frenatus) in Australia’, Austral Ecology, vol.36, no.3, pp. 240-251.

Vanderduys, E.P, Kutt, A.S 2013, ‘Is the Asian House Gecko Hemidartylus frenatus, really a threat to Australia’s biodiversity?’ Australian Journal of Zoology, vol.60, no.6, pp. 361-367.

 

Wild Boars!

Photo by Ashley Barbagello Veiwed on 08/04/2014

Feral pigs (Sus scrofa) are descendants of various sub-species of the domestic pig derived from stock that were let loose or escaped. They occupy a vast range of vegetation from subalpine grasslands to monsoonal floodplains. Their largest concentrations are on the larger drainage basins, and swamp areas of the coast and inland. (Bengsen, et al, 2014)

Feral Pigs, are an ecological, economic and social pest. Their impact on the environment is extensive.  By grazing and rooting they damage pastures, digging up large areas of native vegetation and spread weeds, cause soil erosion, degrade waterholes and wetlands. This digging behaviour can severely disrupt the composition of the soils microorganisms and consequently nutrient cycling. This can also disrupt the regeneration of plants, change the composition of the plant community and allow water erosion to occur in drainage areas where the soil is disrupted. (Bengsen et al 2014)

  Environmental damage is largely through modification of natural habitat, but predation and competition with native animals has also been reported. Feral pigs can also carry disease and parasites that affect stock and people. Through predation of stock, consumption and damage of crops feral pigs cost the agricultural industry alone an estimated $100 million per annum (Lopez et al, 2014).

Photo by Ashley Barbagello. Viewed 08/04/2014

Several methods are practiced to control feral pigs. One effective way to keep pigs out is exclusion fencing; fencing off small high value areas such as cropping or lambing paddocks. However this method is highly costly on time and maintenance and ineffective on large scale areas as well as only relocates the problem rather than contribute to control it.

 Other methods include government trapping programs and recreational hunting via shooting or dogging. It is estimated that hunters kill 15-20% of the feral pig population in accessible areas.  Currently, the most cost effective and efficient control is the use of aerial baiting with 1080 (sodium monofluroacetate) (Barrious-Garcia, Ballari, 2012).  The effectiveness of the baits depend on a few variables as not all pigs within an area will take the baits depending on alternative food availability, pig density within the area and density of baits. One study found that success rates vary form 58% to 99.4% (Hone, 2002). None of these methods have been proven to be stand alone solutions for the complete eradication of the feral pig.

References:

Bengsen A.J, Gentle M.N, Mitchel, J.L, Pearson H.E, Saunders G.R 2014, Impacts and management of wild pigs Sus scrofa, In Australia, Mammal Review, Vol.44, no.2, pp.135-147.

Barrious-Garcia M.N, Ballar, S.A 2012, Impact of wild boar (Sus scrofa) on its introduced and native range: a review, Biological Invasion, vol.14, no.11, pp.2283-2300.

Hone, J 2002, Feral Pigs in Namadgi National Park, Australia; Dynamics, impacts and management, Biological Conservation, Vol. 105, no. 2, pp.231-242.

Lopez J, Hurwood D, Dryde B, Fuller S 2010, Feral Pig Populations are structured at fine spatial scales in Tropical Queensland, Australia, National Parks, vol.9, no. 3.

Rubber Vine, the Rubbish

Photo by Colin G Wilson. Rubber vine smothering vegetation.
Viewed 30.03.2014

Rubber Vine, Cryptostegia grandiflora, endemic to the Island of Madagascar, was introduced to Northern Australia in 1917 in the hope of becoming a rubber source ( Huwer, McFadyen, 1999).  The shrub has since become a serious problem in the areas that it inhabits.

 Rubber vine generally invades waterways first where the seeds germinate in moist silt layers after rain fall. From there it expands outward invading hillsides and pastures forming dense and often inpenetratable thickets resulting in not only a decrease in biodiversity but a loss of grazing land and can make it difficult to muster stock.  In addition rubber vine creates habitat for feral animals, which poses further threat to native species.  Once the thickets are established the plant can cover trees up to 30m tall which choke out native vegetation (McFadyen, Harvey, 1990). The weed is poisonous to stock however it is rarely consumed, only when other feed is scarce.

There have been several mechanisms to conquer this weed. Chemical control is effective as rubber vine is susceptible to many herbicides however this method has proven to be uneconomical due to the vast areas of infestation.  In 1988, Euclasta whalleyi , a leaf feeding moth, also endemic to Madagascar was released as a potential biocontrol agent. It has been effective to a degree, increasing leaf litter which promotes grass growth amongst rubber vine which intern increases fuel loads for fire management. This creates opportunities to use fire as a part of the approach to manage this damaging weed (Tomly, Evans, 2004).

 

 In 1995 a rust fungus, Maravalia cryptostegiae, also from Madagascar was released to areas of the weed’s range in Queensland.  The results showed a rust-induced defoliation, producing an overall reduction in fecundity and biomass of the plant. Particularly in areas with low water tables weed growth decreased noticeably. At some sites both drought and rust induced stressed caused up to 75% plant mortality. This resulted in improved growth of indigenous grasses amongst thickets which creates ideal conditions in order to burn off and control the weed further. In order to gain full restraint over this economically and ecologically damaging weed would require the assistance of the landholders in which the rubber vine occupies.

 

 

Refereneces:

 

Huwer RK, McFadyen R.E, 1999, 'Biology and the host range of the hawk moth Nephele densoi Keferstein (Lep.: Sphingidaw) a potential agent for the biological control of rubber vine Cryptosteyia grandflora', Biocontrol Science Technology, Vol.9, no. 1, p.10.

 

McFadyden R.E, Harvey G.J, 1990, 'Distribution and control of rubber vine Cryptosteyia grandflora weed in North Queensland, Plant Protection Quarterly, Vol.5 no. 4, pp. 152-155.

 

Tomley A.J, Evans H.C, 2004, 'Establishment of and preliminary impact studies on, the rust, Maravalia Cryptopstegiae, of invasive alien weed, Cryptosteyia grandflora in Queensland, Australia, Plant Pathology, Vol.53, no. 4, pp. 475-484.