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INVASIVE SPECIES RESEARCH AND MANAGEMENT UNIT

Towards integrated and sustainable managementof water hyacinth in

Zimbabwe

Fig 1: Management of water hyacinth is a complex ecological problem with many factors interacting

to determine water hyacinth populations

Professor A. B. Mashingaidze

Invasive Species Research and Management Unit, Chinhoyi University of Technology, P. Bag 7724,

Chinhoyi, Zimbabwe

June, 2013

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Introduction

Water hyacinth (Eichhornia crassipes(Mart.) Solms.-Laubach) is a free floating aquatic weed that

grows rapidly forming expansive mats of interwoven floating plants that impede navigation and

access for recreation and fishing, block canals and weirs, clog irrigation pumps, degrades water

quality, depletes oxygen for other aquatic species, reduce biodiversity and is responsible for loss of

up to six times more water through transpiration than from open reservoirs.

Water hyacinth has been a constant and recalcitrant problem in the Manyame river basin inland

lakes and rivers which are contaminated with sewage effluent from the metropolis of Harare and

Chitungwiza (Chikwenhere and Phiri, 1999; Moyo and Phiri, 2002). Other large infestations are

found in rivers and dams around the small towns of Masvingo, Chinhoyi and Rusapeand in Lake

Kariba (Chikwenhere et al., 1999). A country-wide survey by Mpofu (1995) found that water hyacinth

was present in rivers and lakes in all provinces in Zimbabwe, except the semi-arid province of

Matebeleland South. Infestation of water hyacinth in Lake Kariba is increasing and concerns on the

potential threat posed by the weed to economic activities, lake ecology and hydro-power generation

has necessitated the formulation of a joint monitoring and management plan between Zambia and

Zimbabwe(French Fund for the Global Environment, 2005).

Background to the problem of water hyacinth in Zimbabwe

Despite the release of biological control agents; the weevils Neochetina eichhorniae (Warner)and

Neochetina bruchi (Hustache) and the pyralid moth Niphograpta (=Sameodes) albiguttalis (Warren)

in Zimbabwean inland lakes, dams and rivers infested by the weed, water hyacinth mats have

continued to grow out of control with the seasonal peaks and troughs in size of the mats dependant

on the interactions of a number of factors such as temperature, macronutrient (phosphate, nitrogen

and calcium) concentration in the water and the populations of and concomitant damage caused to

the weed by biological control agents. Chemical control of the weed using herbicides 2.4 Dicloro-

phenoxyacetic acid (2.4D) and glyphosate has been incorporated into the management of water

hyacinth in Zimbabwe when weed mats grow out of control, in spite of fierce public opposition

concerned with unintended public health and environmental effects of herbicides (Mashingaidze

and Chivinge, 1995), but with little impact on weed populations, which re-colonize the water bodies

from reserves of dormant seed in lakeshore sediments.

Fig 3: Attempts at manual removal of water

hyacinth have proved costly and largely ineffective

Fig 2: Water hyacinth plants in Lake Chivero

showing damage from Neochetina weevils

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Water hyacinth management is a complex ecological problem. It has one of the highest rates of dry

matter production (Pieterse, 1978), with a capacity to double of 5days (Perkins, 1973) to 11-15 days

(Penfound and Earle, 1948). Water hyacinth reproduces through vegetative extension by formation

of rhizomes and by production of seed. The seed is shed and settles into sediments at the bottom of

the river or lake where it remains dormant for 20 years (Mathews et al., 1977). As many as 3000

seeds are produced per inflorescence with each rosette capable of producing several inflorescences

per year (Barret, 1980). This seed is a source of re-infestation especially when there is a reduction in

water in rivers and lakes which expose sediments to light, oxygen and wetting and drying cycles

which are instrumental in breaking water hyacinth seed dormancy (Sullivan and Wood, 2012). Re-

infestation is observed from the shoreline and bays, where seedling plants emerge from the

sediments and float into water bodies. Reservoirs of dormant water hyacinth seed in sediments

makes it almost impossible to eradicate once it has colonized a water body. In many cases reports of

successful control of this invasive aquatic weed species have been premature because they are

frequently followed by resurgence in water hyacinth populations from re-infestations that occur

from seed banks of dormant seed in sediments below the water line. The implications to sustainable

management of water hyacinth populations is that “silver bullet” approaches which result in the

clearance of the weed such as chemical application and mechanical harvesting give a fleeting but

false impression that the water hyacinth menace has been conquered, only for it to re-emerge and

re-colonize the water bodies.

The weed infestation on Lake Chivero was controlled through a combination of biological, chemical

and mechanical control and declined from 42% in 1976 to 22% in 2000. Re-invasion began to be

noticed in 2005 and included massive amounts of another invasive aquatic weed species, spaghetti

weed (Hydrocotyle ranunculoide) (Chikwenhere, 2001; UNEP, 2008). By October 2012, satellite

images of the lake showed that re-infestation with water hyacinth had probably reached 1976 levels

(UNEP Global Alert Services, 2013). Despite the appearance of spaghetti weed taking over the

vacant ecological niche created by the control of water hyacinth, water hyacinth remains the

dominant and most problematic weed in Lake Chivero and the Manyame river systems in Zimbabwe

(Shekede et al., 2008). Long term surveillance and monitoring of weed populations using remote

sensing and other survey methods (Venugopal, 1998; Shekede et al., 2008) and management of

resurging weed populations is a prerequisite to sustainable long term management of the weed.In

addition studies need to be undertaken to explore the possibilities of stopping seed production by

the weed to break its most important longevity strategy of dormant weed seed banks hidden under

the water in the sediments.

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Water hyacinth populations explode out of control in water with high concentrations of mineral

nutrients especially nitrogen and phosphate associated with disposal of semi-processed and un-

processed sewage and waste water into water bodies and the lack of indigenous biological control

agents that have co-evolved with the weed. Biological control agents for E. crassipes are

Fig 4: May 1989, Water hyacinth in Lake Chivero Fig 5: May 2000, Weed almost controlled

Fig 6: May 2005: Weed begins to re-invade Lake

Chivero

Fig 7: October 2012: Weed has re-colonized

the shoreline

Fig 4-7: Satellite images showing

progressive invasion, control and re-

invasion by water hyacinth in Lake

Chivero, Zimbabwe. Satellite images

and captions adapted from UNEP

Global Alert Services (GEAS), 2013,

page 7.

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traditionally imported from its area of origin in South America include Neochetina eichhorniae

Warner, Neochetina bruchi Hustache, and, later, the pyralid moth Niphograpta (=Sameodes)

albiguttalis (Warren). These three agents, plus the mite Orthogalumna terebrantis Wallwork, are

now widely used throughout the world for water hyacinth biological control.

Recent expeditions into South America have added a list of other potential biological control agents

that potentially can be tested for host specificity to E. crassipes and efficacy to control the weed

(Center et al., 2002). Many countries that have initiated biological control programs against water

hyacinth have reported successes (Julien and Griffiths, 1998). Dramatic successes with biological

control have been reported (Goyer & Stark, 1984; Gutierrez et al., 1996; Chikwenhere & Phiri, 1999,

Ochiel et al., 1999; Julien & Orapa, 1999, de Groote et al., 2003; Ajuonu et al., 2003). Under

favourable conditions, biological control using the weevils N.eichhorniae and N.bruchi can reduce

weed infestations to between 20% and 5% of its original cover within 3-5 years. All four agents are

important, although the two Neochetina weevils seem most successful. Nonetheless, the control

Figure 8.Neochetina bruchi (left) and N.

eichhorniae (right) adults. (Photo courtesy

of W.C. Durden, USDA, ARS.

Figure 9: Neochetina adult weevils typically cause

scarification damage in which the upper epidermis

and underlying leaf tissues down to the veins are

removed leading to necrosis and holing.

Figure 10 : Late-stage Neochetina sp. Larvae feed at

the base of leaf petioles, often damaging subtending

axillary buds. (Photo courtesy of W.C. Durden, USDA,

ARS.)

Figure 11: Waterhyacinth plants stressed by

weevils tend lose buoyancy and to be of small

stature. (Photo courtesy of W.C. Durden, USDA,

ARS.)

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achieved has not always been sufficient. The relatively slow action of the biological control agents is

sometimes incompatible with other management practices (Center et al., 1999). In other cases, the

explosive growth of water hyacinth stimulated by high nutrient levels precludes effective biological

control (Heard and Winteron, 2000).

In the southern African regions including Zimbabwe and South Africa biological control against water

hyacinth has been less successful and this has been ascribed to highly eutrophic waters that allow

luxuriant growth of the plant, cold winters that reduce or wipe out the biological control agent

populations, application of other control methods such as herbicide application and mechanical

removal that may directly affect the agents or cause a catastrophic reduction in the weed population

that decimates the biological agent population (Julien, 2001).Researchers at WITS University found

that above a threshold of 0.1mg/l of phosphate concentration in the water, water hyacinth growth

was excessive and could not be restrained by biological control agents. The phosphorus level of

0.1mg/l threshold, is the level above which water hyacinth growth is unrestrained by phosphorus

availability (Wilson, 2002). In hyper-eutrophic nutrient rich waters with high nitrogen and

phosphorus content, biological control agent populations fail to keep pace and control the exploding

populations of water hyacinth as seen at Lake Chivero and the Manyame river systems in

Zimbabwe.Center and Dray (1992) theorized that plant quality and phenostage influenced the

weevil’s propensity to switch between phases, with N. bruchi being more sensitive to plant quality

(Heard and Winterton, 2000) and more likely to disperse.Both species of Neochetina undergo flight

muscle generation and degeneration (Buckingham and Passoa, 1985), possibly reflecting alternating

dispersive and reproductive phases that are likely to be related to plant quality on which the weevils

are feeding.There is need to carry out studies in Zimbabwe to derive insights into the drivers of

water hyacinth growth and proliferation, its ebbs and flows with seasonal variations in climatic and

water qualityduring the wet and dry season and in different locations of the country. There is also

need to generate information on the relationship between the water hyacinth and the biological

control agents in relation to the climatic and environmental parameters in areas in which water

hyacinth grows in Zimbabwe. This locally specific information on the ecology of water hyacinth and

the biological control agents will enable us to understand why previous management strategies have

Figure 13: An adult male of the pylarid

mothNiphograpta albiguttalis. (Photo courtesy of

W.C.

Durden, USDA, ARS.)

Figure 14: The water hyacinth mite Orthogalumna

terebrantis. (Photo courtesy of W.C. Durden, USDA,

ARS.)

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so far failed to produce the desirable long term impact of reducing water hyacinth populations

below the economic injury and nuisance level and to take remedial action by designing fit-for

purpose sustainable strategies that are in sync with local climatic and environmental variables.

The auxin mimicking phenoxyacetic acid herbicide 2.4D has is used as part of the management of

water hyacinth when weed mats grow out of control and to clear emerging water hyacinth seedlings

emerging from the shoreline in areas previously cleared of the weed in Zimbabwe. However, when

herbicides clear the weed they cause a catastrophic collapse of the weevil population and when

water hyacinth populations resurge, the weevils fail to keep pace and water hyacinth populations

explode. A useful strategy, currently being implemented, is to leave unsprayed refugia for the

biological control agents, to act as a reservoir of biological control agents to re-infest re-emerging

populations of weeds. However, there has been no studies to determine the effect of the size of

these set aside refugia, the distance to newly emerging populations of the weed, the wind direction

and water hyacinth plant quality on biological control agent re- infestation and efficacy to hold back

populations of newly emerging water hyacinth. Sub-lethal dosages of herbicides can potentially be

used to reduce the growth of exploding populations of water hyacinth and allow biological control

agent populations time to build up and keep the weed mats below the economic injury level (Center

el al.,1982) without causing a catastrophic population collapse of the biological control agents.

Application of sub-lethal dosages may elicit production of kairomones that attract biological control

herbivores.Kairomones are allelochemicals of favourable adaptive value to the organism receiving

them (Messersmith and Adkins 1995). The kairomone liberated by water hyacinth when injured by

wounding or 2.4D treatment is a powerful attractant to N. eichhornie and the water hyacinth mite O.

terebrantis. The relationship between damage caused to the weed by the herbicide and release of

kairomones that attract biological control agents needs further investigation to explore if it can be

harnessed in an integrated management programme for water hyacinth.

Invasive Species Research and Management Unit (ISRMU)

The Invasive Species Research and Management Unit was formed by proclamation of the Vice-

Chancellor of Chinhoyi University of Technology after he made an announcement through the press

on 15th August 2012 that the University was going to deploy resources and manpower to carry out

research on water hyacinth and other invasive species to gain insights into long term and sustainable

strategies to effectively manage, first water hyacinth, and second other invasive species, to reduce

the damage they cause to economic activities and the environment in Zimbabwe. The mandate of

the Invasive Species Research and Management Unit at CUT is to carry out research under local

ecological conditions to understand the dynamics in invasive species populations in relation to

environmental, climatic, edaphic and biotic factors and develop integrated and sustainable

strategies to manage the invasive species populations. Because of problems that are currently being

caused by exploding mats of water hyacinth nationwide but in Lake Chivero and the Manyame river

system, in particular, it was decided to start research, advocacy and extension work on the

management of water hyacinth. In addition, the Unit is charged with developing local research skills

in invasive species ecology and management by engaging students at MSc, MPhil and PhD level to do

their theses research on aspects of the biology, ecology and management of invasive species to

generate relevant and durable solutions to the economic and environmental problems caused by

these species. The work of the Unit is predicated on the assumption that locally relevant ecological

information on relationships among invasive species, biological control agents, environmental

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parameters and various control methods can be integrated to come up with sustainable

management strategies for water hyacinth and other invasive species in Zimbabwe.

Structure and thematic areas of study for the Invasive Species Research and Management Unit

To carry out its work the IRSMU is organized into five thematic areas of focus for the research,

advocacy and outreach work on water hyacinth viz. Ecology and Environment,Host-Plant Biological

Control Agent Interactions, Management and Control, Ecological Services and Utilization and

Integration and Modelling. The mandate of theme leaders is to identify research topics under their

theme, write proposals to mobilize research funds and recruit and supervise Masters and PhD

students.

Professor A. B. Mashingaidze, BSc Agric Hons (Crop Science), UZ; MS Agronomy, Iowa State,

USA; PhD Crop Weed Ecology, Wageningen, the Netherlands; is the Director of the Unit. His

responsibility is to provide leadership in consultation with theme leaders in generating and

prioritizing research themes and topics, writing proposals to generate funds for research,

outreach and advocacy activities on invasive species in Zimbabwe and fostering of

collaborative activities with national, regional and international partners. His research

interests and publications are in weed ecology and management and pesticide science. He is

also the leader for the for the Management and Control thematic research area.

Professor T. Bere, PhD Ecology and Natural Resources, UFScar-SP, Brazil; MSc Tropical

Hydrobiology and Fisheries, UZ; BSc Biological Sciences, UZ; is the theme leader for the

Ecology and Environment thematic area. He is a freshwater ecologist with a mounting

research and publication record in the area. His research interests are in river health

assessment, biological monitoring of aquatic systems, aquatic eco-toxicology, ecological

modelling and bio-remediation of freshwater systems.

Dr R. Musundire, PhD Entomology, Pretoria; MSc Crop Protection, UZ; BSc Agric Hons

(Crop Science), UZ; is the theme leader for the Host Plant and Biological Control Agent

Interactions thematic group. He is a research entomologist affiliated to the International

Centre for Insect Physiology and Ecology in Nairobi and with previous experience at

Tobacco Research Board and Plant Protection Institute of D&RSS. His research interests are

in sustainable management of invasive species, host-natural enemy interactions and post-

harvest entomology. He has a number of publications in high impact journals in these areas

Dr C. Murungweni, PhD in vulnerability and resilience of agricultural systems,

Wageningen, The Netherlands; MSc in Animal Science, UZ; BSc Agric Hons, UZ; is the

theme leader for the Ecological Services and Utilization thematic area. He is an

animal nutritionist with 11 years of experience as Head of the ruminant livestock

research unit at Grasslands Research Station. His research interests are in the

formulation of novel home-made diets for ruminant livestock, nutritional

biochemistry and forage science. He has several publications in high impact factor

journals in these areas.

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The Invasive Species Research and Management Unit has a flexible structure and will incorporate

other prominent researchers as new invasive species problems and thematic areas are taken up as

areas of research, advocacy and outreach by the Unit. The basic tenet of the structuring of the Unit

at any given time will be to incorporate qualified and experienced researchers who are capable of

leading teams of Masters and PhD students in carrying out research that will advance scientific

knowledge in invasive species ecology and management.

The following research topics that are envisaged to start contributing locally relevant information for

the development of sustainable and durable strategies for the management of water hyacinth in

Zimbabwe have been formulated. Masters and PhD students are being recruited to start working on

these topics and it is envisaged that they will form a national nucleus of researchers and advocates

for invasive species biology, ecology and management in Zimbabwe.

a) Water quality dynamics and climatic factors in lakes and rivers in Zimbabwe as drivers of water hyacinth exploding populations

b) Water hyacinth and biological control agent interactions in aquatic systems in Zimbabwe c) Feasibility of incorporating sub-lethal dosages of herbicides in the management of water

hyacinth in Zimbabwe-efficacy, ecology and integration d) Novel ways of deriving ecological services from water hyacinth e) Development, parameterization and validation of a decision support model for the

management water hyacinth in Zimbabwe

Budget and Start-Up Activities

To start the research activities, a number of conditions have to be met. First there is need to engage

with a whole range of stakeholders involved in the management and regulation of invasive species in

Zimbabwe such as Environmental Management Agency (EMA), Department of National Parks and

Wildlife, Department of Natural Resources, Plant Protection Institute, City Councils, Watershed

Management Committees, Farmers Associations, academics and regional and international bodies

(Food and Agriculture Organization, IUCN, UNEP) and others. First, we intend to call for a national

conference at Chinhoyi University of Technology on water hyacinth with the objective of forminga

national research networkon water hyacinth and to refine research objectives as informed from the

experiences of other researchers and managers of water hyacinth in Zimbabwe. Second, we need to

build a research facility near the Manyame river which is 200 m from the Chinhoyi University of

Technology campus, where more controlled studies and monitoring of water hyacinth will be carried

out. Third we need to enrol students for Masters and PhD studies on research themes and topics

that we have identified and others that will emerge from consultations withnational stakeholders

during the national conference. Research studentships will be advertised in the national press and

interested candidates invited to produce concept notes with the aid of thematic leaders. The

concept notes will be evaluated by a panel of prominent scientists and researchers for award of

Professor F.T. Mugabe, PhD Water Resources Management, UZ ; MSc Agricultural Water

Management, Reading, UK; BSc Agric Hons (Soil Science) UZ; is the theme leader for the

Integration and Modelling thematic area. He is the current Director of Research and

Resource Mobilization at CUT. He spent 10 years as a research officer at the D&RSS is the

former Dean of the Faculty of Agriculture and Natural Resources (MSU). His research

interests are in water management and modelling and he has a strong publication track-

record in these areas

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studentships. Successful candidates will be employed as research assistants at CUT, however they

will need to be supported to finance their research costs.These requirements cannot be fully met

from Chinhoyi University Budget and an input is required from partners and well-wishers of the

university who want to be associated with world class research, advocacy and outreach activities

that provide sustainable and durable solutions on visible and important national problems like water

hyacinth.

References

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eichhorniae and N. bruchi on water hyacinth, Eichhorniae crassipes in Benin, West Africa. African

Entomology 11 : 153- 161.

Barrett, S. C. H. 1980. Sexual reproduction in Eichhornia crassipes (water hyacinth). II. Seed

production in natural populations. Journal of Applied Ecology 17: 113-124.

Buckingham, G. R. and S. Passoa, 1985. Flight muscle and egg development in waterhyacinth weevils,

pp. 497-510. In Delfosse, E. S. (ed.). Proceedings VI International Symposium onBiological Control of

Weeds. August19-25, 1984. Vancouver, British Columbia. Agriculture Canada, Ottawa, Canada.

Center, T. D. and F. A. Dray, 1992. Associations between waterhyacinth weevils

(Neochetinaeichhorniae and N. bruchi) and phenological stages of Eichhornia crassipes in southern

Florida.

Florida Entomologist 75: 196-211.

Center, T. D., K. K. Steward, and M. C. Bruner, 1982. Control of waterhyacinth (Eichhornia crassipes)

with Neochetina eichhorniae (Coleoptera: Curculionidae) and growth retardant.

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Center, T. D., F. A. Dray, G. P. Jubinsky, and M. J. Grodowitz, 1999. Biological control of

waterhyacinth under conditions of maintenance management: can herbicides and insects

be integrated? Environmental Management23: 241-256.

Center, T. D., M.P. Hill, H. Cordo and M.H. Julien, 2002. Water hyacinth. In: Van Driesche, R., et al.,

2002, Biological Control of Invasive Plants in the Eastern United States, USDA Forest Service

Publication FHTET-2002-04, 413 p.

Chickwenhere, G.P., Keswani, C.L. & Liddel, C., 1999.- Control of water hyacinth and

itsenvironmental and economic impacts at Gache gache in the eastern reaches of Lake

Kariba,Zimbabwe pp 30 – 38 In Hill, Julien & Center (eds), 1999.- Proceedings of the first IOBC

GlobalWorking Group meeting for the biological and integrated control of water hyacinth. Plant

ProtectionResearch Institute, Pretoria, 182 p.

Chikwenhere, G. P. and G. Phiri, 1999. History and control effort of water hyacinth, Eichhornia

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Hyacinth, Harare, Zimbabwe, November 1998, 91–100.

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Chikwenhere, G. P., 2001. Current strategies for the management of water hyacinth on the

Manyame river system in Zimbabwe. In Julien M.H., M.P. Hill, T.D. Center and Ding Jianqing (eds.).

Biological and integrated control of water hyacinth, Eichhornia crassipes. Proceedings of the Second

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102: 105-108. Australian Centre for International Research, Canberra.

de Groote H., O. Ajuonu, S. Attingnon, R Djessou P. Neuenschwander, 2003. Economic impact of

biological control of water hyacinth in southern Benin. Ecological Economics 45 : 105 - 117.

French Fund for the Global Environment, 2005. Pollution monitoring and management on the

Zambezi River: Technical Report: Water hyacinth monitoring and management plan. 38 pages.

Goyer, R. A. and J. D. Stark, 1984. The impact of Neochetina eichhorniae on waterhyacinth in

southern Louisiana. Journal of Aquatic Plant Management 22: 57-61.

Gutierrez E, R. Huerto, P. Saldana and F. Arreguin, 1996. Strategies of water hyacinth ( Eichhornia

crassipes ) control in Mexico. Hydrobiology 340 : 181-185.

Heard, T. A. and S. L. Winterton, 2000. Interactions between nutrient status and weevil herbivory in

the biological control of water hyacinth. Journal of Applied Ecology 37: 117-127.

Julien, M. 2001. Biological control of water hyacinth with arthropods: a review to 2000, pp.8-20. In

Julien, M., M. Hill, T. Center, and Ding, J. Proceedings of the Meeting of the Global Working

Group for the Biological and Integrated; Control of Water Hyacinth, Beijing, China, 9-12

December 2000. Australian Centre for International Agricultural Research, Canberra, Australia.

Julien, M. H. and M. W. Griffiths, 1998. Biological Control of Weeds. A World Catalogue of Agents

and their Target Weeds, 4th edition. CABI Publishing, New York.

Julien, M. H. and W. Orapa. 1999. Structure and management of a successful biological

control project for water hyacinth, pp. 123-134. In Hill, M. P., M.H Julien, and T.D. Center

(eds.) Proceedings of the 1st IOBC Global Working GroupMeeting for the Biological and Integrated

Control of Water Hyacinth.November 16-19, 1998, Harare, Zimbabwe.

Mashingaidze A. B., and O.A. Chivinge, 1995. Demystifying the dioxin controversy associated with

the use of 2.4D to control water hyacinth in Lake Chivero in Zimbabwe. Zimbabwe Journal of

Agricultural Research 33: 1-14.

Matthews, L.J., B.E. Manson and B.T.Coffey, 1977.Longevity of water hyacinth (Eichhornia

crassipes(Mart.) Solms.) seed in New Zealand. Proceedings6th Asian-Pacific Weed Science Society

Conference1968, Vol.1, 263-267.

Messersmith, C.G. and S.W. Adkins, 1995. Integrating weed feeding insects and herbicides for weed

control. Weed Technology 9: 199-208.

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Journal of Ecology 40: 401–406.

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Mpofu, B. 1995. Biological control of water hyacinth in Zimbabwe. PhD dissertation, Department of

Plant Science, Macdonald College of McGill University, Montréal, Québec, Canada.

Ochiel G.R.S., A.M. Mailu, W. Gitonga and S.W. Njoka 1999. Biological control of water hyacinth on

Lake Victoria, Kenya . In: Hill MP, Julien MH & Center TD (Eds) Proceedings of the first IOBC global

working group meeting for the biological and integrated control of water hyacinth, 16-19 Nov,

Harare, Zimbabwe. pp. 115-118.

Penfound, W. T. and T.T. Earle, 1948. The biology of water hyacinth. Ecological Monographs 18:447-

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Pieterse, A.H., 1978. The water hyacinth (Eichhorniacrassipes) – a review. Abstracts. Tropical

Agriculture4(2), 9-42.

Perkins, B.D., 1973. Potential of water hyacinth management with biological agents. In Proceedings

of the Tall Timbers Conference, Ecological Animal Control Habitat Management 1972. pp. 53-64

Shekede, M.D., S. Kusangaya and K. Schimdt, 2008. Spatio-temporal variations of aquatic weeds

abundance and coverage in Lake Chivero, Zimbabwe.Physics and Chemistry of the Earth, Parts

A/B/C 33: 714–721.

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longevity andthe implications for management. Eighteenth Australasian Weeds Conference

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Invasive Species Research and Management Unit Budget Estimates 2013-2016

2013 2014 2015 2016

Item

National conference on water hyacinth research and management

50 Delegates (Travel, subsistence and per diems) 25000

5 Keynote speakers (Travel, subsistence and speakers fees) 7500

Venue hire, hotel rooms, food 5000

Conference bags, stationery 2500

Sub-total national conference 40000

Water hyacinth research unit

Research Infrastructure (Ponds, artificial rivers, insectaries,

pumps, dryers, weighing scales, boats) 70000

Buildings (processing sheds, offices and ablutions, guard room) 75000

Others (Fencing materials, automatic weather station 5000

Sub-total water hyacinth research unit 150000

Research, advocacy and outreach

Regional and international travel 5000 5000 5000 5000

Advocacy/outreach costs (conferences, posters, travel and subsistence 10000 10000 10000 10000

Research funds ( 3 MPhil students at US $20 000 per annum) 60000 60000 60000 60000

Research funds ( 5 DPhil students at US $30 000 per annum) 150000 150000 150000 150000

Sub-total research, advocacy and outreach 225000 225000 225000 225000

Yearly totals 415000 225000 225000 225000