Hydrobiologia 340: 181-185, 1996.J. M. Caffrey, P R. F Barrett, K. J. Murphy & R M. Wade (eds), Management and Ecology of Freshwater Plants.© 1996 Kluwer Academic Publishers. Printed in Belgium.

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Strategies for waterhyacinth (Eichhornia crassipes) control in Mexico

Eric Gutitrrez, Rub6n Huerto, Pilar Saldafia & Felipe ArreguinHydrobiology Laboratory, Instituto Mexicano de Tecnologia del Agua, Apdo. P! 235, CIVAC, Morelos,Mexico 62500

Key words: Eichhornia crassipes, control, management, maintenance control.

Abstract

In Mexico, more than 40 000 ha of dams, lakes, canals and drains are infested with waterhyacinth (Eichhorniacrassipes). To prevail over the problems resulting from this infestation, specific management programs are needed.Under a national program to control the waterhyacinth, guidelines to deal with the related ecological, social,technical and economic factors, and specific strategies to reduce coverage were developed. The ecological factorswhich were noted include the identification of the most affected areas and the consequences of proposed treatments.The social aspects embraced the stimulation of user awareness as to the importance of water quality, the creationof organizations to coordinate user-sponsored control activities, and the awakening of a community identity. Basicto all are the technical and economic aspects which make the activities feasible and operational. Examples aregiven of control by means of water level management, mechanical controls using trituration, and the application ofchemical and biological agents, all of which may be combined in an integral program.

Introduction

Waterhyacinth (Eichhornia crassipes (Mart.) Solms)is successful owing to its life cycle and survival strate-gies which have given it a competitive edge over oth-er species. Its capacity for vegetative reproductionallows the plant to quickly occupy any available space.Regrowth from relatively small plant fragments, floata-bility and the production of viable seeds are efficientmechanisms for the dispersion and colonization of oth-er areas, especially when combined with a minimum ofgrowth-limiting factors, resistance to drying, morpho-logical variety, root-ability, lack of natural enemies andadaptability to little-competed ecological conditionsmake eradication of this plant virtually impossible andcontrol extremely difficult (Perazza et al., 1979; Nifio& Lot, 1983; Gopal, 1987; Luu & Getsinger, 1988).

The basic units of a management program are thecomplex variables related to plant growth and the rela-tionships among them. The tactics and strategies willcombine these units with greater or lesser efficiency.In Mexico, more than 62 000 ha of dams, lakes, canalsand drains are infested with water weeds. Of this total,

40000 ha are covered with waterhyacinth. To over-come the problems resulting from this infestation, spe-cific management programs are needed to reclaim thesebodies of water. Although many variables and factorsinteract under these conditions, the Mexican Instituteof Water Technology (IMTA) has worked to single outthose which may be built into strategies that are bothtechnically and economically feasible.

The Aquatic Weed Control Program (AWCP) wascreated in 1993 to combat the excessive presence ofweeds in the nation's water courses. The objectives ofthis work are to present the main characteristics of theAWCP, and describe the control program implementedin the Ayutla River watershed as an initial stage of alarger national program.

Study area

The Ayutla River watershed comprises three dams inseries, the Miraplanes, Tacotn and Trigomil (Figure1). The mean annual temperature in the area is 20.9 °C

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Figure 1. Water Hyacinth infested areas in the Ayutla watershed

Table 1. Characteristics of dams in the Ayutla Watershed

DAM MIRAPLANES TACOTAN TRIGOMIL

Use Irrigation Irrigation, Irrigation,

fishing fishing

Volume (Mm3) 0.73 149 324

Area (ha) 73 500 393Mean depth (m) 1 20-30 60-80Max. depth (m) 2 40 100

Weed present W/T W WInfested (ha) 73 204.8 211.4

Uninfested (ha) 0 257.5 181.8

Total surface (ha) 73 462.3 393.2

Satellite image (January 10, 1993). W = Waterhyacinth. T = Typha

with an average annual rainfall of 806.5 mm. Table 1provides other related information.

Control program

The AWCP contemplates six phases.

Initial evaluation. The area was observed to eval-uate the infestation and identify the users who aredirectly affected and would be interested in commit-ting themselves to the maintenance phase of the pro-gram in conjunction with government authorities. Thewater uses, aquatic communities, location and types

of crops surrounding the dam, weather conditions andpossible control strategies were identified. The weedcoverage was quantified by means of satellite imagesfrom LANDSAT TM. The resolution of these imageswas 25 m x 25 m per pixel (0.0625 ha).

Participation and communications. Meetings wereconvened with users to provide them with informationconcerning the proposed control strategy, establish usercommitments, organize and define responsibilities forthe short, medium and long term. Informative exhibi-tions were prepared to offer updates, and later training,to the users.

Economic feasibility study. Unit costs for labor,material, infrastructure and administration were calcu-lated, as were costs for the monitoring and follow-upprograms after the control efforts had ended.

Control. The control strategy was developed, basedon the characteristics of each dam, the assigned bud-get, and the most appropriate control techniques avail-able domestically. These latter included herbicidal,mechanical and biological procedures, and water lev-el management (Table 2). Chemicals employed incontrol schemes have been mainly 2,4-D, diquat andglyphosate. The most commonly used mechanicalmethod is a triturator placed on a raft with blades oper-ating at 2000 rpm up to 30 cm below the water sur-face. The waterhyacinth weevil, Neochetina eichhor-niae, has been observed in the three basins. This insectwas introduced to Mexico toward the end of the seven-ties in an effort to establish a biological control (Ben-net, 1984). During this phase, operations began. Thisincluded the programming of equipment and materials,supervision of tasks and quantification of the decreasein biomass.

Environmental monitoring. The elimination ofaquatic weeds by any one of the means customarilyused, modifies the preexisting conditions. In Gutidrrezet al. (1994) a water quality monitoring program isdescribed in which analyses were made prior and sub-sequent to executing the control program. Studies weremade of changes in the planktonic and benthonic com-munities in the affluent and effluent of the dam, andof herbicidal residues in water, sediment and tissues ofedible fish species.

Maintenance. Tactics were developed whereinusers and authorities were firmly committed to main-

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Table 2. Evaluation of waterhyacinth control methods

Alternatives Chemical Extraction Trituration Biological Water level Manual

management

A: Economicfeasibility Good Poor Average Good Good GoodB: Technicalfeasibility Good Average Average Average Average Poor- Availability Good Poor Average Average Not applicable Good

- Transport Easy Average Average Easy Not applicable Easy- Access to water body Good Average Average Good Good Poor- Efficiency 50-100% control 240 m. tons/d 716 m. tonsd Poor to Average 2.5 m. tons/8h/man

in 20-80 days 1.2 ha/8h* 1.7 ha/16h average 0.01 ha/8h/man- Short-term effects Good Good Good Poor Good Poor

- Long-term effects Average Good Average Good Average PoorC: Environmental impact Medium-high Low Medium-high Low Low LowD: Socio-economic conditions

- Personnel training Specialized Intermediate- Intermediate- Not applicable Not applicable Non-specialized specialized specialized

- Foreign currency required No Yes No No No No- Acceptation index Low High Intermediate High to intermediate High High

* Aquamarin H-10, manufacturer information

Table 3. Maintenance control guide for dams in the Ayutla watershed submitted to intensive control.

Infestation Coverage % Control Opportunity

Serious 15-25 Chemical from airboat and/or trituration Immediate

Dangerous 5-15 Chemical from airboat and/or trituration and/or mechanical extraction 7 daysModerate to tolerable 0 to 5 Manual extraction from boat and/or shore, chemical from boat and/or shore 14 days

taining waterhyacinth levels below the problem thresh-old. Criteria were developed relating coverage withrecommended control measures (Table 3). This infor-mation was provided to the user committee, togetherwith training in the procedures listed. Routine inspec-tions were made from previously-identified strategicpoints and the results compared with the criteria. Therecommended control techniques for small scale appli-cation were those least likely to affect the ecosystemand water users. Often these measures were a part ofan integral watershed management program. Mainte-nance control is considered essential in the reclamationprocess, as it is more cost efficient in the medium andlong term, reduces the use of herbicides, lessens theenvironmental impact resulting from the destructionand decomposition of the aquatic weeds, and increas-es the efficiency of biological and mechanical controlmethods (Haller, 1981).

Management strategies

Three different control strategies were developed forthree distinct bodies of water which had in commonneither use, depth, size nor geographic location (Fig-ure 1 and Table 1). Water level management was con-sidered the most adequate for the TacotAn Dam. Thewater was released to the Trigomil Dam, downstreamand 105 ha of waterhyacinth were left to dry on theshore and were burned by the users (fishermen). Theremaining 100 ha were dusted, by helicopter, with 3.3kg ha- of 2,4-D. The dam was then closed for 21 days.This first treatment was 60% effective. The remaining40% was not sufficiently damaged to sink. However,with the combined effect of a reduction in populationand a loss of turgidity, a greater surface area was madeavailable. Diquat, a contact herbicide, was applied 55days later at a rate of 1.7 kg ha-1 and provided 100%control. The dam was cleared after 110 days of opera-tions.

For the Trigomil Dam, a combined chemical-mechanical program was prepared. The water from the

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dam is used in the El Grullo Irrigation District, restrict-ing the time during which the dam may be closed andthe chemical used. Glyphosate (RodeoTM), at 3.35kg a.i./ha, was selected as there are no restrictionson its use in irrigation water. One-half of the infest-ed area (104 ha) was treated initially; the remainderwas sprayed 38 days later. The herbicide's action wasirregular, with some areas showing excellent resultswhile others reacted very slowly. The product wasapplied during the growing season based on resultsfrom small-scale tests performed that indicated greatereffectiveness at that time (Gutidrrez, 1993). Thoughthe plants sank slowly and inconsistently, there wasa noticeable reduction in plant growth in most areas.There was also a marked change in the consistencyfrom strong, healthy plants with an intense green colorto yellow individuals which fragmented easily at thetouch. Sinking was calculated in 20 to 40 hectares. Thesecond dose was applied as scheduled and two tritu-rators began a 15 day campaign to accelerate sinking,after which approximately 160 ha of waterhyacinth hadbeen eliminated and 100% control was attained.

At the Miraplanes Dam (Figure 1), the presence of alarge area of cattail (Typha sp.) affected the decision touse glyphosate. Westerdahal and Getsinger (1988) statethat glyphosate is very effective against this species.Three treatments were programmed. The first was donefrom a small plane at 3.5 kg ha-1 . The second was 25days later, from helicopter at 3.33 kg ha- and the thirdusing the same method 207 days after the first. Fifteendays afterward, 70% of the dam was cleared. Threemonths later, the dam was totally weed-free.

The results of the analyses for residues of 2,4-Dindicated that levels never exceeded 0.1 mg 1-1, themaximum accepted level for drinking water. Residuesof 2,4-D, glyphosate and diquat were not detected inanalyses of tissues of edible fish (tilapia, carp and cat-fish) and sediments. The low levels found in water maybe explained by dilution and degradation, supportingclaims of low persistence (Gutidrrez et al., 1994). Theassimilation of the triturated or treated biomass intothe water column modified its quality by incorporat-ing nutrients and diminishing the dissolved oxygenthrough an increase in the COD. However, the changein quality was due mainly to an affluent in which highconcentrations of organic material and other nutrientswere detected. No dead fish were observed during orafter the treatment period. Studies made of the bio-logical communities (benthic and planktonic) in theTacotAn, Trigomil and Miraplanes dams indicated thatthey were unaffected (Guti6rrez et al., op. cit.). There

was an increase in the number of weevils based on theobservable foliar damage. As a second phase to theprevention program, Neochetina bruchi will be intro-duced to complement the maintenance program.

Suggestions and conclusions

The basis for a soundly-designed control program isearly strategic planning. This means a timely eval-uation of all environmental variables related to theprocess. Morphological characteristics, water use andquality, hydraulic operations, accessibility, relation-ships among users, and plant dynamics are just a fewof these parameters. They must be correlated with thehuman, material and economic resources available.Finally, a cost-benefit analysis will define the mostsuitable alternative for control and maintenance underthe conditions found at each site. To assure the ful-fillment of the expectations of the project, in terms ofscheduling, safety, goals and costs, constant on-sitesupervision is vital. Water quality analyses and aerialinspections are useful guides.

Most of the waterhyacinth control methods havebeen used in Mexico, harvesting by hand and machine,trituration, and treatment with herbicides and biologi-cal agents. Experience has taught us that the first phaseof the control program must employ massive attacktechniques for an important reduction in coverage,such as that seen with the use of chemical agents andtriturators. The second phase should utilize all of themodern know-how combined into an integral manage-ment program to keep the population under the weedthreshold. It is here that biological control can be animportant component. A sustainable control programalso requires a watershed-wide administration programin which all users are involved in the drafting of thealternatives. User involvement serves to stimulate anawareness of the causes and the magnitude of the prob-lem, and to invite his direct participation in the cleaningprocess. In this context, user presence not only ensuresthe success of the restoration, but also reduces costssignificantly.

Acknowledgements

Special recognition is given to Dr William T. Haller andDr Alison Fox from the Center for Aquatic Plants ofthe University of Florida, for their contributions in thedevelopment of the AWCP. Thanks are given to Dianne

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Hayward, for her valuable comments on the finishedwork and translation; to Ernesto Uribe, Eduardo Ruiz,Marco A. Mijangos and Ulises Bucio for their supportin the fieldwork; to Alfredo Tapia for his assistance inthe design and presentation of the manuscript.

References

Bennett, F. D., 1984. Biological control of aquatic weeds. In G.Thyagarajan (ed.) Proc. Int. Conf. Water Hyacinth. UNEP. Nairo-bi: 14-40.

Gopal, B., 1987. Water hyacinth. Aquatic plant studies. ElsevierScience Publishers, Amsterdam, 471 pp.

Guti6rrez, E., 1993. Effect of glyphosate on different densities ofwaterhyacinth. J. Aquat. Plant Manage. 31 (July): 255-257.

Guti6rrez, E., E Arreguin, R. Huerto & R Saldaia, 1994. Aquaticweed control. Int. J. Wat. Res. Devel. 10: 291-312.

Haller, W. T., 1981. Maintenance control of waterhyacinth. Aquatics3(2):6-7, 11-12.

Luu, T. K. & D. K. Getsinger, 1988. Control points in the growthcycle of waterhyacinth. U. S. Army Corps of Engineers. Water-ways Experimental Station. Envir. Lab. Vol. A-88-2: 1-5.

Nifio, S. M. & A. Lot, 1983. Estudio demogrifico del lirio acuftico,Eichhomia crassipes (Mart) Solm. Dinimica de crecimiento endos localidades selectas de Mexico. Boletin de la SociedadBotanica de Mtxico 45: 71-85.

Perazza, W. T., N. D. Pereida & T. M. Martins, 1979. Problematica decontrole de plantas aquaticas. In Anais do 20 Simposio Nacionalde Ecologia. Belem, Brasil, Nov. 19-23.

Westerdahl, H. E. & D. K. Getsinger (eds), 1988. Aquatic plant iden-tification and herbicide use guide. Vol. 1 Aquatic herbicides andapplication equipment. Aquatic Plant Control Res. Prog. Tech.Rep A-88-9. U. S. Army Corps of Engineers. Vicksburg, Missis-sippi, USA, 222 pp.