The Weevils On The Water Hyacinths Biology Essay

In South Africa, H2O jacinth has a steep exponential growing as it is able to turn in a broad scope of environmental conditions. It can be therefore considered as one of the most invasive foreign H2O weeds that threaten South Africa ‘s waterways. It blocks the waterways, therefore forestalling drainage and pilotage. It besides impedes the growing of autochthonal aquatic life in the waterways. The aquatic weeds grow in mats that cover the surfaces of the organic structures of H2O. This prevents sunlight from making the aquatic workss beneath the surface, which consequences in their inability to photosynthesise. Water jacinth has a widespread distribution across South Africa, therefore ensuing in many environmental and economic impacts, every bit good as troubles with the control of the aquatic weed.

The intent of this research undertaking is to find if the degrees of foods in the H2O affect the sum of eating of the weevils on the H2O jacinths. Water hyacinths obtain the foods that are necessary for their growing from the H2O in which they are situated. Many of these foods accumulate in the H2O as a consequence from the leaching of fresh foods in fertilisers from commercial farms, every bit good as the drainage from sewage Stationss. This research undertaking will find if the degrees of phosphates and nitrates in the H2O are increasing the sum of eating by the weevils on the H2O jacinth. It will therefore bespeak if methods need to be introduced to further command the concentrations of foods that are leaching into the H2O, and if the control of these foods will help in cut downing the troubles in the biological control of H2O jacinths. This research undertaking will help in doing South African ‘s aware of their parts, which are largely indirect, to the growing of the H2O jacinths.

The findings of the research should be utile to:

The direction of the commercial farms and sewage Stationss, who should be made cognizant of the impacts that the drainage of foods from these constitutions has on the biological control of the H2O jacinth. This would help in promoting these constitutions to take a greater involvement in the control of these foods.

The experts and research workers who are involved with the biological control of the H2O jacinths

Civilian South Africans who are passionate about the saving of South Africa ‘s waterways and autochthonal aquatic life, so that they are made cognizant of the impact that they have on the environment

Literature Reappraisal:

Water jacinth ( Eichhornia crassipes ) is a free-floating aquatic works that is widely considered as one of the universe ‘s worst H2O weeds. It is a brilliant Amazonian works with beautiful and fragrant purple flowers ( Joubert, 2009 ) . The foliages of the H2O jacinth are glistening and of a dark green coloring material, in rosettes with easy identifiable conceited leafstalks, which assistance in maintaining the works afloat in the H2O. The works was introduced into South Africa because of these aesthetic qualities. Water hyacinth foremost appeared in South Africa on the Cape Flats in 1908, and was about instantly introduced into Kwa-Zulu Natal at about the same clip ( Joubert, 2009 ) . Since its first visual aspect, the remotion and control of the jacinths has been unsuccessful in South Africa. This is debatable as the jacinths have many negative impacts on South Africa ‘s environment, society and economic system. This literature reappraisal will bespeak one of the chief factors that limit the success of the control of the jacinth, every bit good as how this factor encourages the growing and success of the H2O jacinths.

The hyacinth workss organize free-floating mats which cover the surfaces of H2O organic structures and obstruct H2O ways, therefore choke offing H2O supply systems, drainage canals and hydro-power generators ( Marshall, 2003 ) . These aquatic weeds besides disrupt pilotage by boats ( Joubert, 2003 ) . The heavy screen of weeds reduces and prevents visible radiation from perforating through the H2O. This prevents submersed aquatic workss from photosynthesisng to bring forth nutrient, which disrupts ecosystems within the H2O organic structures. The fecund growing of the H2O weeds besides causes a lessening in the O and an addition in the C dioxide within the H2O organic structures ( Jones, 2009 ) , which aids in the break of the ecological operation of the autochthonal aquatic life signifiers. The jacinth besides causes H2O loss through transpiration which is clearly greater than the loss of H2O from unfastened H2O through vaporization ( Marshall, 2009 ) . Due to the fact that the dense mats of this aquatic works disrupts the flow of H2O, doing dead H2O to happen, H2O jacinth provides suited genteelness sites for vectors of disease.

Due to all of these negative impacts of the H2O jacinth, different methods of direction have been implemented to help in the control of H2O jacinths. Mechanical, chemical and biological methods have all been implemented in the hope of commanding the workss ( Kluge, RL. 1978 ) . Since 1974, six species of biological control agents have been introduced into South Africa ( Coetzee et al. ) . Two species of weevils ( Neochetina eichhorniae and Neochetina bruchi ) , a moth ( Niphograpta albiguttalis ) , a touch ( Orthogalumna terebrantis ) , a foliage sucking capsid ( Eccritotarsus catarinensis ) , and a infective fungus ( Cercospora piaropi ) . These biological control agents damage the tissues of the works, and they kill the roots, flowers and seeds, thereby cut downing the workss resources ( Coetzee et al. ) . Despite the high Numberss of agents that are released, more than anyplace else in the universe, successful biological control has non yet been achieved in South Africa. This is due to certain factors such as the remotion of the weed through implosion therapy, climatic mutual exclusiveness and the presence of many nutrient-enriched H2O organic structures in South Africa ( Coetzee et al. ) .

Water jacinths spread the best in Waterss that are polluted with fertiliser run-off ( Joubert, 2009 ) , as they can absorb big concentrations of N and phosphoric from the H2O organic structures. Other subscribers to these high degrees of foods and phosphates are the waste merchandises of worlds and animate beings ( Marshall, 2003 ) .

An probe was conducted on the consequence of pH and high phosphoric concentrations on the growing of H2O jacinth by the University of Florida ( Haller, WT & A ; Sutton, DL. n.d. ) . Research that was antecedently conducted on other aquatic workss, was besides analysed. The findings of the probe, when compared to the old research, indicated that H2O jacinths absorb every bit much as four times the phosphoric than the other aquatic workss that had been studied ( Haller, WT & A ; Sutton, DL. n.d. ) . The high concentrations of phosphoric that were absorbed by the jacinths depended on the phosphoric content in the H2O. This indicates that the H2O jacinths do non absorb a fixed concentration of foods, which therefore allows them to boom in nutrient-enriched Waterss, as they can absorb most of these high degrees of foods. Findingss in the probe besides indicated that increased degrees of phosphoric in the H2O, resulted in the increased growing and productiveness of the H2O jacinths ( Haller, WT & A ; Sutton, DL. n.d. ) . The probe concluded that the debut of H2O jacinths in to H2O organic structures that suffer from eutrophication would help in cut downing the degrees of foods. Although this is true, it has been found that the H2O hyacinths thrive excessively good in nutrient-enriched Waterss and, therefore, can non be controlled. Therefore this decision has been invalidated as the H2O jacinths would be an uneffective execution to cut down eutrophication in H2O organic structures.

At phosphoric degrees below 0.06mg P/l the jacinths are expected to decease. Between 0.06mg P/l and 0.1mg P/l the workss can last but are non really successful. Levels between 0.1mg P/l and 1.06mg P/l will ensue in the active growing and success of the jacinths depending on N degrees. Maximum growing occurs at a nitrogen concentration of 21mg N/l ( Coetzee et al. 2011 ) . This information was recorded in 2005, when the South African Water Research Commision ( WRC ) commenced an probe to prove certain thoughts for bettering the biological control of H2O jacinths ( Coetzee et al. 2011 ) . The findings of the probe were published by Byrne et Al. 2010. The probe aimed to find the factors that were restricting the success of the biological control, and so aimed to work out these issues by implementing new thoughts. Although the survey was less clear, the probe aided Coetzee et Al. ( 2007 ) and Byrne ( 2009 ) in reasoning that higher food degrees aided the H2O jacinths in lasting the harm created by the biological control agents ( Coetzee et al. 2011 ) . The findings of this probe indicated that the biological control of any aquatic works becomes progressively hard as the food degrees, in the H2O in which the workss are situated, addition.

The web site of the University ( 2013 ) of the Witwatersrand quotes Hill & A ; Cilliers ( 1999 ) in saying that one of the major factors that limit the biological control of the H2O jacinth is the inordinate eutrophication of South African waterways. Harmonizing to the National Eutrophication Monitoring Programme ( n.d. ) “ eutrophication is the procedure of the inordinate alimentary enrichment of Waterss that typically consequences in jobs associated with macrophyte, algal or cyanophyte growing ” , and in this state of affairs, the growing of H2O jacinths. The causes of eutrophication in South Africa are alimentary tonss in agricultural, urban and industrial overflow, every bit good as in discharges from sewage intervention programs. Eutrophication has a assortment of damaging impacts on South Africa. Examples of ecological impacts are the loss of biodiversity and the consequence of toxins that are released into the H2O from the bacteriums that are booming in the nutrient-enriched Waterss. Water intervention costs contribute to economic impacts. Other impacts are the break of the recreational utilizations of the H2O organic structures, every bit good as human wellness impacts due to the toxins that are released ( National Monitoring Programme, n.d. ) . Eutrophication is one of the major causes for the broad distribution of H2O jacinths across the South Africa ( Joubert, 2009 ) . Eutrophication decreases the efficaciousness of biological control.

A research survey was performed by the Faculty of Animal, Plant and Environmental Sciences at the University of the Witwatersrand in 2007. The purpose of the probe was to find the impact that the concentrations of foods in the H2O had on the biological control of the H2O jacinth. It was determined that at high alimentary concentrations productions of foliages and girl workss were dual than at lower food degrees ( Coetzee et al. 2007 ) . The lengths of roots were besides double at high food degrees when compared with low food degrees. The chlorophyll content was besides double at high food concentrations than at low concentrations ( Coetzee et al. 2007 ) . These findings indicate that higher food degrees encourage the success of the H2O jacinths. They besides indicate that biological control would be deficient to cut down the Numberss of H2O jacinths at such high concentrations of foods.

Harmonizing to all of these research probes, high degrees of foods in the H2O promote the growing and development of the H2O jacinths, every bit good as promote their distribution. It is apparent that this is one of the chief factors that have limited the success of biological control of the jacinths in South Africa, as South Africa ‘s waterways and H2O organic structures experience terrible instances of eutrophication. This promotes the spread and growing of the jacinths as the workss are better suited for endurance in nutrient-enriched H2O. What has non been clearly indicated in the literature findings is how the food degrees in the H2O negatively affect the biological control of the jacinths. My future research undertaking will hopefully bespeak if the concentrations of foods in the H2O straight affect the sum of eating by the weevils on the jacinths. This will find one of the ways in which the concentrations of foods in the H2O impact the success of biological control. The research will besides bespeak the demand for methods of the control of the degrees of foods in the H2O, in order to assistance in the success of the biological direction of H2O jacinths.


Four bath of the same size and volume, each filled with 80 liters of tap H2O, will be used in this research probe. Three healthy, free-floating H2O jacinth workss of the same size and at the same phase of development will be placed into each bath, with all dead foliages and stems removed. The 80 liters will be measured utilizing a pail that is filled with 10 liters of H2O by a measurement jug. The degree of the 10 liters of H2O will be marked off, and therefore the pails will be used to mensurate a volume of 10 liters of H2O, which will be used to accurately mensurate out 80 liters of H2O for each bath.

The followers are descriptions of the contents of each bath:

Tub 1 will incorporate 80 liters of H2O, 8g of Fe chelates, and three H2O jacinth workss that are infested with 5 weevils each.

Tub 2 will incorporate 80 liters of H2O, 8g of Fe chelates, three H2O jacinth workss that are infested with 5 weevils each and 24g of 7:1:3 fertiliser.

Tub 3 will incorporate 80 liters of H2O, 8g of Fe chelates, three H2O jacinth workss that are infested with 5 weevils each and 48g of 7:1:3 fertiliser.

Tub 4 will incorporate 80 liters of H2O, 8g of Fe chelates, three H2O jacinth workss that are infested with 5 weevils each and 72g of 7:1:3 fertiliser.

The concentrations of nitrates and phosphates will be calculated utilizing ratios, and the given information of the bag of fertiliser. The bag states that the fertiliser has a nitrate concentration of 95g N/kg and a phosphate concentration of 14g P/kg. Using ratio computations, these concentrations will be converted to concentrations measured in mg/l, as this is the standard unit of measuring for the foods concentrations in H2O.

To mensurate the sum of feeding performed by the weevils, the eating cicatrixs on the foliages will be counted at the terminal of each 7 twenty-four hours hebdomad for the continuance of the experiment. To guarantee that feeding cicatrixs will non be twice counted, threads will be tied around each foliage and root that has already been counted so as to guarantee truth. Feeding cicatrixs will be counted as they clearly show the sum of feeding that has occurred on each works after each hebdomad, therefore decisions based on the sum of eating by the weevils will be able to be made by looking at the figure of feeding cicatrixs. The eating cicatrixs besides indicate the harm that has been done to the works, and will therefore allow for decisions to be made on the success of the biological control of the H2O jacinths. Photographs will besides be taken each clip readings are taken, so as to supply a digital certification of the development of the probe. The exposure will besides supply support of the honestness of the informations aggregation, so as to turn to any ethical issues environing the honestness of the informations aggregation.

60 weevils will be used during the class of the probe. Their intervention will be humanist and cruelty-free, guaranting that none will be deliberately harmed by a human. This will extinguish any ethical issues environing the intervention and usage of the weevils in the probe.

As the probe involves the usage of invasive foreigner workss that are already debatable society, there are ethical issues environing the usage of these workss. In order to extinguish the presence of these issues, careful stairss will be taken in the attention of the workss. Each clip a reading is taken, it will be ensured that all that comes in contact with the workss and that may transport its seeds, such as custodies, is cleaned and washed and ensured that all works stuff is removed. The H2O jacinth will stay in the bath which ensures that they are removed from any running H2O, such as pipes in the gardens. Careful steps will be taken in the disposal of the workss, to guarantee that they are decently disposed of in the right manners, which includes decently cleaning all the bath that contained the H2O jacinths.

Apparatus list:

Permanent marker

4 baths of the same size and volume


Measuring jug

Hosepipe and H2O beginning

Electronic graduated table

4 plastic bags

144g of 7:1:3 fertiliser

32g of Fe chelates

Blue thread

Red, green and xanthous thread

60 weevils

12 healthy, free-floating H2O jacinth workss


Method of probe:

Using the electronic graduated table step 8g of Fe chelates and topographic point in a fictile bag.

Repeat measure 1and fill the other three plastic bags with 8g of Fe chelates each.

Using the electronic graduated table, step 24g of 7:1:3 fertiliser and topographic point in one of the plastic bags.

Near the bag.

Repeats stairss 3-4 for measurings of 48g and 72g of 7:1:3 fertiliser to be placed severally in the 2 other plastic bags.

Near the last plastic bag, incorporating merely Fe chelates

Set out the four bath.

Using the lasting marker label each bath as ‘tub 1 ‘ , ‘tub 2 ‘ , ‘tub 3 ‘ and ‘tub 4 ‘ .

Using a measurement jug mark off 10 liters of H2O in a pail utilizing a lasting marker. Ensure that the pail is set on degree land.

Use the pail to make full each of the four bath with 80 liters of H2O from a hosepipe.

Remove the dead roots, foliages and other dead stuff off of 12 single, healthy H2O jacinth workss that are of the same size and at comparatively the same phase of development.

Topographic point 3 single H2O jacinth workss in each bath.

Tag each works to distinguish between them in order for informations aggregation. Tie the pieces of thread around the longest chaff of each works. In each bath: utilize a piece of ruddy thread for works 1, a piece of green thread for works 2 and a piece of xanthous thread for works 3.

Pour the contents of the plastic bag incorporating merely 8g of Fe chelates into tub 1.

Pour the contents of the plastic bag incorporating 8g of Fe chelates and 24g of fertiliser into tub 2.

Pour the contents of the plastic bag incorporating 8g of Fe chelates and 48g of fertiliser into tub 3.

Pour the contents of the plastic bag incorporating 8g of Fe chelates and 72g of fertiliser into tub 4.

Count the figure of feeding cicatrixs on the foliages of a jacinth works by taging each of the foliages that have been counted with pieces of bluish thread.

Record the informations in a tabular array.

Remove the bluish thread from the works once all of the eating cicatrixs have been counted.

Repeat stairss 18 – 20 for each works in the bath.

Repeat stairss 18-21 on the same twenty-four hours every hebdomad for the following 8 hebdomads.

Analyse the informations by plotting line graphs and finding the relationships between the variables. If the eating scars addition as the alimentary concentrations addition, it will bespeak that the weevils will hold an inauspicious impact on the workss.

Data Collection:

The information gathered will be recorded in a table format:

Independent variable: the concentrations of nitrates and phosphates measured in mg/l.

Dependent variable: the figure of feeding cicatrixs per works