Sustainable Taro Culturein the Pacific

The Farmers' Wisdom

Table of Contents

Soil Conservation 1Soil Fertility 3Weed Management 5Insect Management 7Disease Management 9Conclusion 11

Introduction

In the Pacific Islands, taro has always been richly woven into thefabric of life. In 1989, the US Department of Agriculture'sLow-Input Sustainable Agriculture Program funded a study of taroproduction systems in the American-affiliated Pacific Islands . Theprimary purpose of the study was to document and test traditional orcurrent methods of crop protection, soil conservation, andmaintenance of soil fertility. During the first year of the projectinterviews and surveys were conducted in American Samoa, Hawaii(the Big Island), Guam, the Northern Mariana Islands, Palau, Yap,Ulithi, and Pohnpei . Insect, weed, and disease checklists werecompiled, as well as informal interviews of farmers, wholesalers ,retailers, and others. This handbook summarizes the information thatwas gathered and supplements a videotape entitled , "Nourish theRoots, Gather the Leaves ." Reports of each island's survey werepublished as Taro Production Systems in Micronesia , Hawaii , andAmerican Samoa. Proceedings from the September 1992 conference,"Sustainable Taro Culture in the Pacific Islands," are available, aswell as the results of further experiments testing some methods oftaro production. For information on these publications, concact theADAP Home Office.

Larger terraces built into slopes create flat steps. In wetlandtaro, water is channeled from terrace to terrace. These taropatches act as traps for silt that would otherwise flowdownstream into the ocean. Diversion ditches can also becreated across slopes to channel water away from fieldswhen there are heavy rains . In low-lying areas near theocean in Palau , berms are used to prevent erosion caused byhigh tides. Plantings on dikes between wetland terracesprovide food, medicine, mulch , and green manure, and theystabilize the dikes as well .

When clearing land , trees can be left in the steepest areasand upslope from fields . In the fields themselves , treetrunks are left so the web of their rootshelps hold soil. Using a triangular plantingpattern breaks the flow of water betweentaro plants, as does planting along thecontour of the slope. In American Samoa,rocks are sometimes placed in circles aroundeach taro plant. Planting with digging stickscauses little disturbance to the soil surface.Even with tractors, minimum tillage canbe used so that only a small furrow isopened up when planting.

In windy areas, windbreaks can

prevent soil from being blow..n<ct:~~~~~~away as well as create a ...better environment for ,----:--";:':,;J,I'-LU,' r~

the growth of thetaro .

o.Ge­<e-{"'<'

Coconut husk

2

Soil Fertility

Despite their small land areas , the Pacific Islands havesustained taro production over the centuries by using onlylocally available resources to maintain soil fertility.

Maintaining fertil ity with shorter or nofallow periods requires adding greenmanures and other soil amendments.Some common green manures areleaves of banana, croton, mango,Hibiscus tiliaceus, panax, differenttypes of grasses, Cassia alata(ringworm cassia), forest treesgrowing nearby, slashed weeds,and coconut husks. In wetland

taro patches green manures arestomped or turned by hand

into the thick mud.

-~-'\"Mulch withanimalmanure,weeds,mac nuts . :coconutleaves

Agroforests of bananas, yams , kavaJawa (Piper methysticum),breadfruit , and coconut grow up around taro plantings. Rootsof these crops gather nutrients from different areas of the soilprofile . As the canopy fills in the spaces between the trees,less light is available for lower-canopy crops , and taroproduction is rotated to recently cleared areas. In these areas ,soil fertility builds up during the fallow period. Tree roots tapnutrients from deep zones of the soil, and tree leaves fall tothe forest floor where leaf-mulch accumulates and decays.Fallows of grass , legumes , and weeds are also commonly

found in the Pacific Islands.Today , as populations grow and developmentpressure on the land increases, there is atrend toward shorter fallow periods . Insome areas , taro was traditionallymonocropped for extended periods oftime without fallowing.

3

Nitrogen-fixing plants have bacteria that live symbiotically(the intimate living together of two dissimilar organisms in amutually beneficial relationship) on their roots, giving theplants the ability to use nitrogen from the air rather than justfrom the soil. In American Samoa a nitrogen-fixing speciesof Erythrina, commonly called gatae, is interplanted withtaro and is left in fields during fallow periods. Loppingsfrom the gatae are placed around the taro plantings. InGuam, our survey teams saw kudzu used in taro fields.

Mulches that prevent soil erosion and shade out weeds(coconut frond husks and mats, banana, cut grasses orweeds, breadfruit, and other tree leaves) also add to thefertility of the soil as they break down.In areas where tractors are used, grassesand other plants that grow up during thefallow are plowed in before taroplanting. Other additions to the soilsometimes include ashes, fish gutsoup, goat manure, pig manure(composted with macadamia husks byone Hawaii farmer), and rusty iron (onAsor, Ulithi). On atolls, organic soils arecreated in pits and tanks that are filledwith coconut fronds, husks, and trunks.Animals, such as pigs, kept in fallowfields can also add to soil fertility.

Chemical fertilizers are used most frequentlyin Hawaii, Guam, and American Samoa.Some growers do not use them becausethey notice an undesirable change in tasteof the corms. One farmernoted that too much fertilizercan cause rot on the bottom ofthe corms. Others are awareof the potential pollution0~~~~~==:-=~~problems in groundwater and surfacewaters .

4

Weed Management

Every taro grower knows that weeding is a labor-intensivejob that can become the major cost of production. Crops canbe lost to weeds as other duties or outside employment drawpeople away from tending their taro .

Hand-weeding has been a family task everywhere in thePacific and is still the most common method of weedcontrol . In some places children and women do most of theweeding . Today machetes and sickles are used to cut weeds,leaving roots intact to prevent soil erosion . Other toolsinclude hoes , picks , and thejuscinos (a hoe made originallyfrom whaling tools in Guam) .

Cut or pulled weeds are allowed to dry andplaced between taro rows as mulch, addingto soil ferti lity and helping to shade outnewly germinating weeds. Other mulchesused to keep down weeds include leaves ofbanana and breadfruit; macadamia nute: husks; coconut leaves, husks, and old mats;~ betelnut wastes; and cardboard .~ In the wetland taro patches of Hawaii0- water levels are raised to drown

weeds during tarogrowth . Azolla orduckweed shadesthe surface of thewater, keepingtemperatures, as

~ell as weeds , down. In addition,

a nitrogen-fixing blue-green algaeliving in azolla leaves

~nut

m5

can provide a large amount of nitrogen to crops. Weeds arepushed into the mud in wetland patches and added toplanting beds in dryland taro, but they can cause diseaseproblems.

Some taro varieties grow faster in the beginning than others,giving them a better ability to shade out weeds. Spacing taroplants closer together (in Guam, 2 feet by 2 feet (.6 meter by.6 meter) and in Hawaii, 1 foot by 3 feet (.3 meter by .9meter)) also helps shade the area between plants faster,decreasing the light that can reach weeds, thereby decreasingtheir growth. Intercrops that quickly cover the groundbetween taro plants also have this effect.

In Guam and Hawaii , rototillers andspringtooth harrows are used tomechanically cultivate weeds.Herbicides are used in Hawaii,Guam , and sometimes AmericanSamoa. The cost and difficulty offindingpeople to hand-weed are the main reasonsfarmers use herbicides.

Frequency of weeding varies quite a bitbut most dryland farmers weed two to fourtimes over the life of the crop. On all islandssurveyed, growers believe that once the taroreaches its maximum growth, it should nolonger be weeded. Because weeds aremostly shaded out, disturbing the groundaround the maturing corms could cause Mulchthem harm or create areas fordisease to enter.

JQ~Mac nuts

6

Insect Management

The most common pests of taro in the areas surveyed wereplanthoppers, rose beetles, aphids , homworms , andarmyworms.

Agroforestry and intercropping can slow the spread ofpests by creating a confusion of smells, making it moredifficult for pests to find the taro growing amidst otherplants . Taller crops and trees can create barriers that are hardto get beyond . Predator populations prefer habitats of mixedcrops rather than monocropped fields. Predators of taropests help keep populations low by parasitizing eggs oreating pests. By rotating crops grown in a field and movingtaro to another area, insect populations that depend on taroto survive will not have the opportunity to build up tounmanageable numbers . Insome areas, fields that have large

pest populations are fallowed for a year ormore to stop the populations fromincreasing.

InAmerican Samoa, Coleus blumei orpate is frequently interplanted with thetaro . Some believe that pate will repelplanthoppers and armyworms. Otherscontend that pate attracts theplanthoppers , which then feed on itsjuices and die from its toxic properties.

Another method of controlling theplanthopper in American Samoa is

through smoking ortorching.

• " .~N)--\,~

7

Handremoval

Coconut leaves are bundled, then set afire and carriedthrough the fields, causing the planthoppers to jump off theplant. It is believed that the planthoppers die as their wingsget burned, or that the smoke drives them away from thefield in large numbers. This practice is done three times aweek until all the planthoppers are gone. The smokingmethod is sometimes thought to be effective against thearmyworm as well.

Armyworms or armyworm egg masses are smashed orhandpicked and sometimes burned. Chickens are oftenbrought in or raised around the plantation because they

reportedly pick the armywormsfrom the plants. The scratchingand feeding of the chickensaround the base of plants wascited as a good weed controlmethod as well as a way ofaerating the soil.

Soap solution is sometimes applied to taro to decrease leafaphid populations. In general, few insecticides are usedbecause insects do not usually pose a severe threat. nSometimes malathion or diazinon are j)~P

used, if they are legally available. Themost damaging insect is the root aphid, a h: r~

fairly new pest on the Island of \.l ~Hawaii, which can cause yields to f1decrease by more than 50%. Currentlythere is no good control measure for theroot aphid. Insect and disease problemscan easily be spread through plantingmaterial , so quarantines Soap and water

should bestrictly followed.

8

Disease Management

Sun Protecting taro crops from disease isthe most difficult task facing the

grower. Both corm rots and leaf blightscan severely decrease yields, in some

cases destroying an entire crop . Somecommon diseases of taro leaves include Phytophtlwra

leaf blight, ghost spot, southern blight , and dasheen mosaic virus.The most common corm rot is Pythium.

Fields that have suffered severe disease infestations can befallowed from one to four years . Without the taro host plant to liveon, some disease organisms cannot survive. If the disease hasother hosts (such as Phytophthora leaf blight on banana), theymust also be removed . Crop rotation, or growing crops other thantaro , can have the same effect.

Some growers believe that taro grown in soils with high fertilityand high levels of organic matter is less likely to suffer fromdisease problems. In Palau ash and coral lime are added to the soil.In Hawaii lime is added and some farmers apply extra potassiumfertilizer, especially in the last half of the crop to prevent Pythiumcorm rot and loliloli, a hardening of certain areas of the corm,which occurs in over-mature taro .

Farmers understand the importance of using clean plantingmaterial . Corm rots are easily spread to other fields with diseasedplanting material . To ensure that no diseases are being spread tonew plantings, some growers use a general-purpose cleaningsolution. A 10% diluted bleach solution is made by adding 1 partof liquid household chlorine bleach to 9 parts of water (just over1 1/2 cups of bleach per gallon of water). When

mixing and using bleachsolution, wear rubber

gloves, eye shield,

~and other protective

>;::0~ ") clothing as neededA'~ rI to avoid contact

'- with the bleach .b~Disease-free

planting 9material

Diseased plants should be removed from the fie ld when theyare noticed . In Palau, the diseased plants are sometimesburied . In Pohnepi , leaves infected with blight are removedfrom the field and sometimes burned. In cases of severeinfestations , all the leaves may be removed from all the plants .Some farmers believe that leaf blight is worse in certainseasons and they adjust planting times to avoid growing taroduring those periods. Certain varieties are believed to be moreresistant to disease than others . Growers in Palau will plantdifferent varieties in one field to test theirresistance. Over-mature taro left in thefield is usually more susceptible tocorm rot , but this also varies withthe cultivar.

In Hawaii it is believed that aconstant flow of water in wetlandtaro will keep soil temperatures lowerand thus decrease disease incidence .Furrows between divisions in the taropatches in Palau increase the flow ofwater and are thought to prevent rootsfrom one section from enteringanother, thus preventing the spread ofdisease . In Palau , weeding afterspreading mulch is thought toincrease the chance of diseaseentering through broken roots .For the same reason , growers inmany places no longer enter fieldsafter taro plants cover the ground.

Planting in sunny areas can helpdecrease the survival of leaf blight

spores . Planting tar~O~f:u~rt~h!e~r=~~!!;~,:~apart may decrease therate of spread of leaf Intercroppingblight.

10

Conclusions

The challenge before us is to combine the best of the old and thenew methods of growing taro in ways that are culturally appropriateas well as environmentally and economically sound . The continuedexchange of information among farmers and other agriculturalworkers may make the way easier to find . We hope that our bookletmakes a small contribution to this exchange and encourages othersto continue their efforts .

Thank you

The Taro Production Systems in theAmerican Pacific, Low-InputSustainable Agriculture Taro Projectis grateful to the taro growers andothers who made this projectpossible by giving so generously of

~ their time, knowledge, and wisdom.

Disclaimer

Mention of a trade name or description of a pesticide use is in noway intended as an endorsement of the product or arecommendation to the exclusion of other suitable prod ucts notmentioned . The mention or description is provided for theconvenience of the reader. The individuals and organizationscontributing to or supporting this publication make no claim ofproduct warranty. Before making any pesticide application, the usermust read the product label; all safety and use precautions on thelabel should be followed.

The information contained in this booklet was gathered from taro growers in interviewsand surveys conducted in 1989-1990 on seven island groups in the American-affiliatedPacific . It is a summary of commo n practices in use by those farmers .

LISAfTaro Project ResearchersAmerican Samoa Agnes Vargo and Fuifui Tao tuaGuam Harley Manner, lise Schreiner, Frank Cruz, and John BrownHawaii Dwight Sato and Lisa FerentinosNorthern MarianasLoli ta Ragus, Hardy Richards, and Isidoro CabreraPalau Meresbang Ngiralmau and Robert BishopPohnpei Willi am RaynorYap Marjorie Falanruw

Thi s booklet was compiled by Lisa Ferentinos based on reports prepared by theseresearchers.

Updated by Kristie TsudaJune 2000Cover graphic by Miles Hakoda , College of Tropical Agriculture and Human Resources ,University of HawaiiIllustrations by Penny Levin

Publ ication was supported in part by a grant from the USDA/CSRS SustainableAgriculture Research and Educati on Program (formerly called LISA). Support was alsoprovided by Ame rican Samoa Community College , College of Micronesia, NorthernMarianas College , University of Guam, and University of Hawaii under the auspices ofthe Agricultur al Development in the American Pacific (ADAP) Project.

This material may be copied for educational purposes. Please credit the Taro ProductionSystems in the American Pacific, LISA Project.

Additional copies may be obtained by writing:Agricultur al Development in the American Pacific (ADAP) Project3050 Maile Way, Gilmore 2 13College of Tropical Agricu lture and Human ResourcesUniversity of Hawaii at MaonaHonolulu , HI 96822 USAFax 808-956-6967adap @hawai i.edu

Ame rican Samoa Community College · 684.699.1575 • fax 684 .699.5011College of Micronesia . 691.320.2462 • fax 691.32 0.2726

College of Mic ronesia (FSM) • 691 .320.2480 • fax 691.320.2479College of the Marshall Islands • 692 .6253236 • fax 692 .625 .4699Palau Community College • 680.488.2746 • fax 680 .488 3 307

Northern Marianas College • 670 .234 .9023 • fax 670.234 .0054University of Guam • 671 .735.2002 • fax 67 1.734 .5600University of Hawaii • 808 .956.8 140 • fax 808.956 .6967

Funded by the United States Departme nt of AgricultureCooperative State Resea rch, Education, and Extension Service Grant 99-38826-7854The Pacific Land Grants and the USDA are Equal Opportunity I Affi rmative ActionInstituti ons