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>