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Pandanus is mostly found on the eastern edges of littoral rainforests and mostly listed as endangered species (Brideson, 2012, 1, 6). Fraser Island is home to the Pandanus tree which is a common tree species in the Pacific coastline extending from Queensland to the southern regions of the Pacific islands. Pandanus has cultural significance to the Aborigines of Australia ranging from food in form of their fruits to its value for shade. The tree is listed as an endangered species because it is the only one found in the area and in recent years there has been increased dieback due to attack by an insect called Pandanus plant hopper (Jamella Australiae). This paper analyses this problem and formulates a design experiment to determine if the dieback is being caused by Jamella infestation or by some other causes.
Pandanus plant hopper insect is mostly found in northern Queensland where adult hoppers grow up to 8mm long. The female flatid lays eggs on the underside of Pandanus leaves usually in groups called egg rafts which contains 50-80 eggs (Elevitch, 2006, 575, 3). The hopper moves by hopping (jumping) from one tree to another or flying for short distances and their spread is mostly favored by warm climate. In the northern Queensland where they originate, the plant hopper is preyed on by wasp larvae. Being the only predator for the plant hopper, the wasp’s absence leads to increased infestation of Pandanus tree by the plant hopper.
The insect feeds on the tree’s sap while smearing the leaves with a sticky substance called honey dew. This substance encourages growth of moulds on the leaves which eventually leads to death of the leaves and eventually the tree. The plant hopper can cause death of a mature tree in 6 months (Queensland Department of Environment and Resource Management, 2010, 8, 5).
Pandanus palm trees have suffered dieback which has become severe in recent years. The leaves first turn yellow, then become covered with mould, die and fall from the trees. The tree then dies from its point of growth when left untreated. When the dieback was first noticed, the Jamella Australiae was also noticed. As explained above, the insect lays eggs on the leaves of the Pandanus tree then covers the leaves with a sticky substance that encourages growth of mould where the dying process begins. The predator of the insects is not found in the Fraser Island because it is not its natural habitat.
The Pandanus tree is widely spread in the pacific coastline with Fraser Island being one of its habitats. The variable of growth area is to be ignored in this experiment. The southern pacific coastline is cooler than the northern region including Queensland (M, 2005, 1, 1). The temperature variable is also to be ignored because the Pandanus and the Jamella can survive in both conditions. The dieback is noticeable simultaneously with the presence of Jamella Australiae. This is a variable to be considered because the researcher would be looking to measure if the Jamella is responsible for dieback.
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The intervention process is yet an important variable which would help to determine if prevention of the spread of the insect by introduction of wasp has any effect on the die back rate (Coastal Foreshore Vegetation Restoration Project, 2011, Para 8). This would also help to inform the researcher on the recommendations to make towards containment of the pandemic. It is also important to determine whether the dieback is caused by other factors other than the insect infestation. It is therefore important to conduct research and collect data on dieback rate on trees not infested by the insect. This means the sample should contain untainted trees and infested trees.
Conceptual model to explain dieback of Pandanus in Fraser Island (Baxter, ENVM7001 Environmental Management Principles and Approaches, 2012, 1, 27)
To determine if the die back in Pandanus trees in the Fraser Island is caused by infestation by Jamella Australiae, the following hypothesis is to be tested (Smith, 2011, Para 3).
- If dieback is caused by infestation of the Pandanus by Jamella then the rate of dieback is greater on infested trees.
- If the dieback is caused by other causes other than infestation by the Jamella, then the rate of dieback should be uniform for all trees (infested and un-infested).
- If the rate of dieback is due to infestation by the Jamella, then introduction of wasps in Fraser Island can reduce the rate of dieback.
This research uses the scientific research method to design an experiment to test the hypotheses. It will involve collecting data through observation, developing a hypothesis and carrying out a controlled experiment so as to come up with a precise conclusion (Hypotheses, 2012, Para 4).
Number of infested trees that die = y
Total number of infested trees sampled = t
Number of un-infested trees that die = x
Total number of un-infested trees sampled = p
Die back rate in infested trees, n = y/t
Die back rate in un-infested trees m = x/p
The Sampling method used in this experiment will involve a stratified random sampling method for identification of the research samples (Baxter, ENVM7001 Environmental Management Principles and Approaches, 2012, 35). The Fraser Island with Pandanus trees will be identified according to the infestation by Jamella Australiae. The strata may therefore be infested strata or un-infested strata. Individual trees will be marked randomly, scattered over the area in one stratum which is infested by Jamella and another one that is not infested. Data collected will be the number of trees that die in a certain period among the selected sample.
Sampling method is stratified random. Data collected will be the number of trees that die in a certain period among the selected sample. Rate of die back for infested trees and un-infested trees is measured as outlined above.
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Sampling method is stratified random. Data collected will be the number of trees that die in a certain period among the selected sample. Rate of die back is measured when wasps are introduced for infested trees.
If die back rate ‘n’ is greater that die back rate ‘m’, then hypotheses one and three are true. However, hypotheses three is only true if ‘n’ for hypotheses one is greater than ‘n’ for hypothesis three. If die back rate ‘n’ is greater than ‘m’ in two, then the hypothesis two is not true and more research should be conducted.
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