Pacific Kava

 

 

A producer's guide
Secretariat of the Pacific Community, Suva, Fiji Islands, 2001

Copyright Secretariat of the Pacific Community 2001

 

All rights for commercial / for profit reproduction or translation, in any form, reserved. The SPC authorises the partial reproduction or translation of this material for scientific, educational or research purposes, provided that SPC and the source document are properly acknowledged. Permission to reproduce the document and/or translate in whole, in any form, whether for commercial / for profit or non-profit purposes, must be requested in writing. Original SPC artwork may not be altered or separately published without permission.

 

Original text: English

 

 

Secretariat of the Pacific Community Cataloguing-in-publication data

Pacific kava : a producer's guide

 

1. Piper methysticum. 2. Kava Diseases and pests. 3. Kava Planting. 4. Kava Harvesting. 5. Kava Post harvest losses Prevention.

I. Secretariat of the Pacific Community

 

583.952 AACR2

AgDex 182

 

ISBN 982-203-810-0

 

 

 

 

 

 

Prepared for publication at the Secretariat of the Pacific Community,
Suva, Fiji Islands, 2001

 

Contents

Introduction                                              5

I. Production                                               6

A. Site selection                                          6

B. Planting material                                     7

C. Direct planting                                        8

D. Nurseries                                               9

E. Transplanting                                        16

F. Planting and spacing                              16

G. Cropping methods                                17

H. Soil and plant nutrition                           20

I. Weeding                                                21

J. Water requirements                                22

K. Pruning                                                 22

L. Pest and disease management                23

II. Harvesting                                             26

A. Harvesting and yields                             26

B. Harvesting techniques                            27

III. Postharvest handling and marketing       28

A. Washing                                                28

B. Cutting and sorting                                 28

C. Drying                                                   28

D. Storage                                                 31

E. Commercial parts of the kava plant         32

F. Kavalactones                                         33

G. High quality kava                                   35

H. Quality specifications                             37

I. Advanced processing                              40

J. Marketing                                               41

IV. Conclusion                                           43

APPENDIX A: Hawaiian kava production  44

Different soils                                              44

Basket system                                             45

Fertility management                                    45

Weed management                                      46

Irrigation                                                     46

Spacing and shading                                    47

Pruning                                                        47

Fast propagation method                             48

Organic kava production                             52

APPENDIX B: False kava                          53

Bibliography                                                55

Glossary                                                      57

Introduction

 

Kava (Piper methysticum Forst. f.) is a Pacific plant species of the pepper family. Following its initial discovery, domestication and diffusion throughout the Pacific kava has become an integral part of Pacific Island religious, economic, political and social life. Its cultural significance is immense and these functions are still a vital part of life today. In recent years the uses have expanded, the range of kava products has diversified, and the demand for kava now comes from people all over the world. Kava has moved away from being a traditional crop for ceremonial and personal use. It is now an important cash crop both for the local market and for export.

Kava production in the Pacific has a long history. The plant has been domesticated for around 3000 years. There is a very large body of traditional knowledge about kava production. However, many farmers are unaware of the production systems used in other parts of the Pacific. This guide is for agriculture extension staff to use with farmers and for progressive farmers. It has been written to supplement traditional knowledge and to encourage experimentation, adaptation, and the use of improved farming practises. As the growing conditions for kava vary greatly throughout the Pacific, it is recommended that farmers experiment with new techniques on a small scale before adopting them on a large scale.

The guide contains the principles for producing high quality kava as a commercial crop for both the domestic and the export market. A range of improved farming methods is described. Producing the quality of kava needed for the export market has been a difficult challenge for Pacific Island growers and exporters. The guide includes chapters on the chemical properties of kava and on the standards that are recommended for the increasingly discerning domestic and export markets. These standards are especially important if Pacific Island farmers and exporters are to continue supplying the overseas pharmaceutical market. The production and marketing of high quality kava is essential if the industry is to grow in the Pacific.

This book is the result of a collaborative effort over a long period of time. Much of the technical information is based on previous publications by Dr Vincent Lebot. He generously allowed the reproduction from this material. Mr Jerry Konanui of the Association for Hawaiian Awa and Mr Jim Henderson of Puu'O'Hoku Ranch contributed the section on kava production methods in Hawaii. Other information has been adapted from the sources listed in the bibliography. The guide would not have been possible without the considerable input from many other contributors. The initiative and support of participants at the Regional Kava Meetings in 1997 and 1998 who recommended the writing of a production guide is appreciated. Dr Richard Beyer, Professor Bill Aalbersberg, Ratu Jo Nawalowalo, Reg Sanday, and Dr Ron Gatty are acknowledged for their advice and guidance. The contents of this publication and any errors contained therein remain the responsibility of the compiler.

 

Tom Osborn

SPC Agriculture Adviser

I. Production

A. Site selection

One of the most important decisions a farmer needs to make is selecting a suitable site for growing kava. Kava is a shade-loving plant. For the young plant to develop properly, care should be taken to shelter it from the sun's rays and the wind. The sun speeds up moisture loss from the plant and causes it to wilt. Winds bend stems and branches and may cause them to crack or break and thus encourage disease in the plant.

In traditional farming, the ideal site for growing kava is mixed cropping fields that have been recently cleared and planted. For example, kava can be planted in fields with taro, maize, yams and sweet potatoes. In these fields the other crops provide the shade that kava needs particularly when it is small. As these other crops mature and are harvested the kava plant gets additional space for growth.

Kava is grown under a wide variety of conditions but the following points are important.

· To allow for vigorous root growth, soils should be fertile and loose but not allowed to dry out. Mulch can be useful on some soils.

· Avoid soils that are prone to waterlogging since this can inhibit growth and cause root rot. For this reason kava is often planted on sloping land; ridging (mounding up soil) can be used for planting kava on flat land.

· Provide shade and protection from the wind for the young plants.

Kava is well suited for Pacific farming systems because it is flexible in its cultivation requirements and thrives in the shade during its first three years of growth. It grows well in traditional multicrop gardens, cut from the forest and partly shaded by taller crops such as bananas and papayas. In most islands of Vanuatu, organic kava production involves crop rotation, intercropping (with peanuts and sweet potato), and planting of windbreaks, shade trees, and leguminous tree species.

 

B. Planting material

There is a substantial diversity in kava cultivars of the Pacific. Many of the differences are in the appearance of the plant (plant morphology) such as the colour of the stem, length of the internodes, stem thickness, and shape of the leaves. There are also differences in the content of kavalactones in different cultivars. Surveys and research indicate that the greatest diversity of kava cultivars is in Vananau with 80; there are 13 in Hawaii, 12 in Fiji, 7 in Tonga, 6 in Samoa, 4 in Papua New Guinea, 3 in Wallis and Futuna, 3 in French Polynesia, and 2 in Pohnpei.

Despite this diversity kava in fact has a very narrow genetic base. This is because kava does not produce viable seed so there is no possibility of cross pollination to create new cultivars. The diversity of kava has been caused by farmers selecting mutant kava plants with desirable characteristics for personal and ceremonial use. This selection system began with the domestication of kava thousands of years ago and has produced the kava cultivars that we have today.

Experienced growers know that one of the most important decisions in producing quality kava is the selection of planting materials. The first aspect is that the cutting must come from a desirable kava cultivar, one with good drinking characteristics. Secondly, the cutting must be from a healthy and vigorous plant. Diseases can be spread from unhealthy kava plants to the surrounding plants and cause great losses.

The normal method of propagation is to use stem cuttings of one to four nodes in length, but the process varies according to area. Either shoots or stem cuttings can be used, and cuttings can be either planted in a nursery or directly planted in the field.

  • Planting material checklist:
  • · Carefully select planting materials from vigorous, healthy plants.
  •  
  • · Carefully inspect stems selected for cuttings to ensure they are free from mealy bugs and scale insects.
  • · Use the more rot-resistant woody mid-portion of the stem for good root and crop development.
  • · Avoid using the soft upper portion of the stem because it is prone to rot and does not easily develop roots and shoots.
  • · Do not use lateral branches for planting material because they will produce plants with horizontal stems.
  • · Do not buy planting material from unknown sources because it may carry plant diseases or may be of poor drinking quality.

One-, two- and four-node stem cuttings are often used for planting material.

C. Direct planting

In many Pacific Islands the traditional planting method has been to plant the stem cuttings directly in the field. There are a variety of techniques. A handful of one- and two-node cuttings can be planted together in a 30 cm (12 in) diameter circle. In some places, four- to six-node cutting are planted vertically with several nodes in the soil. Sometimes cuttings are rooted in loose soil before planting. Often the cuttings are planted and covered with soil and a layer of mulch to retain moisture since adequate moisture is critical for the root and shoot development.

However, direct planting of kava stems has been abandoned in many areas for the following reasons.

· Direct planted kava requires more planting material and longer pieces. The demand for planting materials is usually high and farmers want to use their planting materials efficiently so they can plant as large an area as possible or so they can sell planting material.

· Kava cuttings require moist conditions at the time of planting to develop shoots and roots. Drought or water stress during this early periods of growth can kill the emerging shoots and roots. Watering young plants is much more costly and time consuming in the field than in a nursery.

· The desired spacing can be difficult to achieve with direct planting because not all the cuttings will produce plants.

· Weed competition with young kava seedlings is a problem that requires considerable labour input and can slow the growth of the young kava plant.

· Young plants require shade and it can be difficult to provide sufficient shade in the field compared with a nursery.

D. Nurseries

Shortages of planting material caused by the expansion in production has stimulated interest in kava nurseries. In several countries nurseries are very successfully used for the propagation of kava and are preferred to the direct planting propagation method. Often when direct planting kava larger cuttings are used, germination of the cuttings is low, and later even plant survival is low. Nurseries use planting material more efficiently and there is a higher survival rate of the plants when transplanted to the field. One- or two-node cuttings, as well as larger cuttings, have been successfully used for propagation in the nursery.

It has been observed that root and shoot development can be affected by:

  • (a) the kava variety some root more easily and quickly than others;
  • (b) the age of the plant two- to three-year-old stems are the best; and
  • (c) the portion of the stem used avoid the soft upper portion and very woody lower portion.

A study of the different kava varieties in Vanuatu showed that some varieties were more difficult to propagate than others. Varieties with short internodes provided cuttings which were very resistant to plant disease during sprouting and the early stages of growth. Cuttings from varieties with long internodes were susceptible to rotting before and after sprouting, particularly in the rainy season. In addition, the shoots of varieties with dark coloured stems developed very slowly.

If you want rapidly growing healthy vigorous young plants, careful management of the nursery is essential.

 

Location of the nursery

The nursery should be located on well drained land to avoid being waterlogged or flooded during heavy rains. There should be access to water for irrigation of the young kava seedlings during dry periods.

 

Soil for the nursery

Rich topsoil, sand and compost, and other media such as potting soil can be used. Potting soil has the advantage that it has been sterilised, which will reduce problems with soil-borne diseases attacking the young plants. Another good mix is 10 parts soil, 1 part sand, 1 part timber shavings or sawdust from untreated timber. It is important that the soil is loose and that it doesn't dry out. Heavy clay soil should be avoided in the nursery since it can become too wet and this encourages the development of fungus in the plants.

Some farmers plant the cuttings in beds of soil with compost. Others use plastic bags (polypots) that make it easier to transfer young plants to the field, but these are more expensive.

Shading is important for the kava cuttings in the nursery.

Watering

Keep the soil moist but not too wet. The nursery should be checked daily to ensure the soil doesn't get too dry. The use of sand, timber shavings or compost in the soil can help the soil from becoming too wet.

 

Weeding

Soil and sand used in the nursery will contain weeds and weed seed. These weeds should be carefully removed to avoid competition with young kava plants.

 

Shading

Kava requires shade. A structure with palm fronds is adequate for shade though 30­50% shade cloth can also be used. Remember not to place seedlings too close to the edge of the shade structure since it will expose them to direct sunlight at some times of the day.

Before the seedlings are removed from the nursery they should gradually be exposed to the direct sun for a week to avoid stress to the plants when they are put into the field. This process is called hardening off the plants.

This can be accomplished by gradually removing the palm fronds from the nursery roof. The shade cloth can be removed for part of each day.

 

Time in the nursery

Plants are generally ready for transplanting when they are at least 30 cm tall (10­12 in). It is difficult to predict how long it will take the seedling to reach this size because of differences in soils, kava varieties, size of cuttings, quality of the cutting, and watering, but generally 3­5 months is sufficient. The seedlings can be kept in the nursery until conditions in the field are right but if transplanting is delayed the shading should be removed to avoid tall plants with weak stems.

 

Advantages of nurseries for kava

  • · Nurseries are adequately shaded to promote development and prevent the cuttings from drying out.
  • · Seedlings can be watered more easily in a nursery than in the field.
  • · It is easier to judge the desired spacing when you plant strong, healthy seedlings in the field.
  • · Seedlings can be placed in the field at a time when moisture and shade conditions are best for plant growth.
  • · Using seedlings can reduce initial weed competition problems in the field.
  • · Weeding time and other labour costs are reduced because the transplanted seedlings are bigger and stonger and need less care.
A well-maintained kava nursery.

Kava nursery methods

Choose the method that best suits your needs. Each method has its advantages and disadvantages.

 

Method 1: planting one- or two-node cuttings in nursery beds.

Take the cuttings when the plant is harvested. Select the woody mature stems, 2­3 years old, which are around the outside of the crown. Young (non-woody) cuttings tend to rot quickly whereas these woody cuttings are very rot-resistant. Woody cuttings are also less prone to damage when they are transported.

When the kava stem is cut into pieces use a sharp knife that makes a clean cut. It is very important to cut the stem near the node and not in the middle of the internode. The soft tissue in the internodes is prone to rot. The microorganisms which rot the inside of the stem seem to have difficulty getting in if only the hard internode is exposed.

Two-node cuttings require more planting

material but they will develop faster than one-node cuttings. When there is a shortage of planting material one-node cuttings can be but the disadvantage of one-node cuttings is that they will not develop as fast as two-node cuttings.

Dig a bed in the nursery 4 m (13 ft) long, 2 m (6° ft) wide and 15 cm (6 in) deep, and cover the bottom with a layer of soil very rich in organic matter or compost, to a depth of about 10 cm (4 in). Lay out the cuttings lengthwise and spaced about 10 cm (4 in) apart to make it easier when digging up and transplanting. Lay another layer of earth about 3 cm deep gently over the cuttings and water very thoroughly (see diagram below).

Cuttings should be horizontal with bud scars facing up. Whether the cuttings have one or two nodes, this method encourages a very high propagation rate and the seedlings will have vigorous root systems.

A well-shaded kava nursery.

Method 2: planting one or two node cuttings in plastic bags

This is the same as Method 1 except that instead of using beds the cuttings are placed in polypots. Polypots are strong black plastic nursery bags with holes in the bottom for drainage, and are available in a variety of sizes. Polypots are commonly used in commercial nurseries. The polypots for kava should not be too big or they become too heavy to transport. Use a 1 litre (1 quart) size bag that is approximately 7.5 cm (3 in) in diameter and

30 cm (12 in) tall to allow space for root development. The cuttings are planted horizontally in the polypot with the bud scar at the top.

Polypots are popular for kava nurseries because they keep the roots of the kava seedlings from growing together and this reduces the risk of damage to the roots when they are transplanted into the field. The disadvantage of this system is the cost of the bags and the cost of transporting seedlings in polypots to the field.

Kava cuttings growing in polypots in a nursery.

Method 3: germinating whole kava stems in the nursery beds

Kava harvesting, cleaning, cutting, and drying requires a lot of labour, but harvest time is also the best time to get the nursery beds established with fresh kava stems. Farmers in Vanuatu have developed a clever system that overcomes the labour bottleneck during this period.

Dig a shallow trench in the nursery approximately 15 cm (6 in) deep and 150 cm (5 ft) wide. Remove the soft upper stem and very woody lower part of the stem. Place the remaining middle portion of the kava stems in the trench and cover them with soil. Keep the soil covering the stems moist. Under these conditions the buds on the nodes will start to sprout and grow. After three to four weeks, one or two roots and leaf shoots will have emerged from each node.

Place the stems in the nursery bed and cover them with soil.
Cross section of sprouting kava stems in the nursery bed.
 

Carefully uncover the kava stems to reveal the shoots and roots that have developed from the nodes. Then cut the stems into one-node pieces, each containing a shoot with one or two leaves and roots. Place the pieces in polypots and put in the nursery to grow until large enough to be planted in the field.

This method overcomes the problems of fungus entering the individual one- and two- node cuttings that can cause them to rot and not sprout.

       
             Kava stems in the nursery

Method 4: planting four-node

cuttings in plastic bags

     
          Polypots in the nursery ready for kava cuttings.
Cross section of polypot with two cuttings.
Cut the middle portion of the kava stem into four-node cuttings. Plant two four-node cuttings upright in soil and compost in polypots that are 16 cm (7 in) wide and 34 cm (14 in) tall. Two of the nodes must be below the soil surface and the other two above. Although this method uses more planting material, the seedling will grow faster and be more vigorous.
Potted kava shaded by shade cloth.
Kava nursery with long cuttings in Pohnpei, Federated States of Micronesia, under tree shade.

E. Transplanting

Transplanting should be done when:

 

  • · the kava plants are 30 cm (12 in) tall so that they are large enough to avoid competition from weeds;
  • · moisture conditions in the field are good; and
  • · the land has been properly prepared and cleared of weeds.

Remember to gradually expose the plants to direct sunlight before removing them from the nursery.

Take care to avoid damaging the roots during transplanting when the polypot is removed and the seedlings are placed in the holes. If the soil is dry each hole should be watered before the seedling is placed in it. Even though the seedlings are 30 cm (12 in) tall they still can't compete with aggressive weeds. Keep the area around the seedlings free of weeds during this initial period. The plants must be well shaded to reduce competition with grass weeds and avoid moisture stress.

Take care after transplanting the kava seedlings. If there is a drought period after transplanting, water the plants to avoid moisture stress and possible wilting or death of the seedlings. The period after transplanting is critical. The plants need time to become properly established before they start to grow well in the field.

 

 

 

 

 

 

 

 As the kava grows farmers regularly ridge or mound up the soil around base of the plant to encourage the appearance of new shoots and discourages weeds.

Trials at Tagabe Agricultural Station in Vanuatu show that it is good to plant on ridges 80 cm (2° ft) wide and 40 cm (1 ft) high. The ridge permits good soil drainage and root growth.

F. Planting and spacing

Preparing the soil

In traditional kava farming methods soil preparation is minimal, and involves simply and rapidly breaking the soil up with a planting stick. Kava often does not receive the care in cultivation normally given to root crops that require the soil to be broken up to a fine texture.

Normally, kava is planted together with root crops in subsistence gardens on recently cleared ground

G. Cropping methods

Intercropping

Kava's natural habitat is under the shade of large trees with a diversity of other plants, and it is still most commonly grown in association with other crops. Experience and research have shown that intercropping has its advantages. It is believed that intercropping can inhibit the spread of disease among kava plants whereas monocropping seems to encourage it. This is an important point in favour of intercropping because it can help prevent the establishment and spread of of devastating diseases like kava dieback.

There is no clear picture of the best combination of crops. It appears that more commonly than not kava is grown with many different crops in the same field.

In intercropping the crops are changed over the growth cycle of the kava. When the kava plants are small, intercrops that provide shade, such as taro and pigeon peas, are helpful. Later, when the kava needs more sunlight, intercrops such as sweet potatoes and peanuts which provide good ground cover are useful.

Kava and coconuts in Taveuni, Fiji Islands.

Kava and coconuts

Intercropping kava and coconuts is a common and natural association for Vanuatu. The spacing used is important. Coconuts have shallow, fibrous roots that extend along the ground well beyond the canopy of the fronds. These roots can compete with the kava plants and make harvesting difficult. Falling fronds or coconuts can also be destructive to the kava.

Depending on the size of the coconut palms and soil and water conditions, a distance of 4­5 metres between the coconuts and the kava may be necessary to avoid root competition. Ridging the kava can also help overcome root competition.

Spacing between kava plants in the row is often 2 m (6° ft), but 1 m (3 ft) may be sufficient.

Coconut­kava intercropping in Vanuatu.

Kava and sweet potato

The intercropping of kava and sweet potatoes is quite popular and effective in Vanuatu for a variety of reasons. The sweet potatoes cover the soil and crowd out the weeds but do not compete with kava for light. The sweet potatoes provide food from the plot for the farm family while the kava cash crop grows. Coconut frond mulch can be used around the kava plants to conserve moisture and supress weeds. The coconut frond mulch can also prevent sweet potatoes from growing too close to the kava and creating root competition.

A disadvantage of this intercrop is that rats are sometimes attracted to the sweet potatoes and they can also feed on the kava.

 

Kava and peanuts

Like sweet potatoes, peanuts provide good ground cover to suppress weeds. Peanuts can be a food crop or a cash crop for the farm family. There is also the advantage that peanuts are a nitrogen-fixing legume that enriches the soil.

 

Kava and ginger

Planting kava with ginger can be difficult because of the nematode problem associated with ginger. The same kinds of nematodes that attack ginger can also attack the kava. For more information on nematodes see page 24.

Kava and vegetables

Kava is sometimes grown with a variety of vegetable such as tomatoes, Chinese cabbage, English cabbage, capsicum, and eggplant. Kava is vulnerable to many diseases that may be associated with vegetables. There is concern that the diseases that attack vegetables can also be transferred to kava through the soil, water, wind and insects. Consequently growing kava with vegetables should be avoided.

 

Kava and taro

Kava is often grown with taro because it provides shade for the young kava plants. Care should be taken to avoid competition for water and nutrients when the two crops are planted too close together.

This form of intercropping has been quite successful on the island of Pentecost, Vanuatu, where the spacing used between kava and taro is 1 m (3 ft).

 

Kava and pigeon pea

Pigeon pea can be an effective plant for intercropping with kava. It is a vigorously growing legume that fixes nitrogen in the soil and the leaves can be used as a nitrogen-rich mulch. It will provide shade to the kava and function as a windbreak. The pigeon pea can be planted while the kava seedlings are growing in the nursery. This way the pigeon pea

Kava can be planted between rows of pigeon peas for shade when the plants are young.

will be large enough to provide shade by the time the kava is planted out in the field.

The pigeon pea and kava are planted in alternate rows. For good shading, which is needed when the kava is young, the pigeon pea can be planted densely and then thinned as the kava grows.

 

Monocropping

Monocropping of kava is not encouraged in the Pacific Islands because this method has the potential to promote the development and spread of disease and it is not good for long-term soil fertility.

Although good coverage of the soil by the kava plants is desired, close planting and little spacing between plants can lead to problems. Closely planted kava monocropping in high rainfall areas creates a lack of air circulation between plants and damp conditions develop that lead to onset of disease.

In Vanuatu, young farmers looking for a quick income are developing monoculture systems for kava (see diagram below). Fields are planted at a very high density of one plant per square metre (10,000 plants per hectare) and after two years of growth, half of the plants are uprooted to allow more space for the 5,000 remaining plants. After another year, when the plants are three years old, half of them are harvested and 2,500 plants are left to grow for up to five years. According to these farmers, this intensive system does not affect kava growth. Vanuatu's volcanic soils are rich but more research is needed to understand the advantages and disadvantages of this system.

H. Soil and plant nutrition

The soil should have good drainage. Even though kava can be grown on a wide variety of soils, the plant prefers deep, loose soils, moist but well drained. The roots of kava have little tolerance for the oxygen starvation that occurs in poorly drained or heavy clay soils. In poorly drained soils the plant is also susceptible to bacterial or fungal diseases. Kava is often grown on hillsides, where drainage is much better than on the valley floor.

Being a plant of forest habitats, kava requires soil rich in organic matter, which provides the nutrients it needs. Kava is a very heavy feeder. Its vigorous growth depends on rich soils and attention to soil fertility management. Traditionally the planting of a kava crop starts with the clearing of the forest, but in most areas this is not a practice that can continue. In Pohnpei State, in the Federated States of Micronesia, the continued clearing of forests for kava has become a major environmental issue. In Vanuatu, for example, a kava crop is planted after two rotations of peanuts, which improve the soil, assist in weed control, and provides extra income for farmers.

Kava has a very limited root system compared to other plants that live as long or grow as big as it does. The root system does not extend very far laterally from the plant or very deep since it doesn't have a tap root. To find nutrients that are not mobile in the soil, roots must grow into new soil. This only happens during the first three years of growth. After three years of growth, the roots have taken

I. Weeding

Weed competition is a major problem in kava production and has led to the use of herbicides. But herbicides should be avoided, for these reasons:

· There has been insufficient research into herbicides for kava production.

· Kava is known to be very sensitive to some herbicides, resulting in wilting even when the herbicide is used some distance from the plant.

· The use of herbicides is prohibited on kava marketed as organic.

The weeding hoe should not be used too close to the kava plant. Serious damage can be caused to the surface roots and adventitious roots from the stem and to the young shoots. It is best to weed between the rows or ridges starting about 50 cm (20 in) from the edge of the plant.

There are many strategies to avoid weed competition in kava:

· Raise seedlings in a nursery and transplant young plants into the field to avoid competition when the kava plant is very small;

· Use intercrops such as sweet potatoes or peanuts that provide good ground cover between the plants and between the rows. When one crop is harvested replace it with another one so that full ground cover is maintained over time.

· Use black plastic mulch to reduce weeds and maintain soil moisture. Black plastic mulch is available in rolls a meter wide. It is laid down on the top of a row and secured with soil around the edges. Holes are made in the plastic and the kava is planted in the holes.

· Use mulch on the soil. The mulch can be made from dried weeds of species that will not resprout. Palm fronds can also be useful.

 

all the nutrients from the soil. The kava plants can then suffer nutrient stress making the plant highly susceptible to disease. After two to three years, composting, mulching, and the addition of animal manure are needed to maintain healthy vigorous plants. This is essential in areas prone to disease problems.

Key points for soil fertility

  • · Mulching provides nutrients and prevents moisture loss.
  • · Manure from pigs, chickens, cattle or horses, makes good fertiliser.
  • · Compost can help maintain soil fertility.
Black plastic sheets can be used to suppress weeds and retain moisture.

Cut grass is a useful mulch.

J. Water requirements

The cultivation of kava is recommended only in high rainfall areas. Kava requires average temperatures ranging from 20 to 30°C and high humidity. At altitudes of less than 400 m, the plant requires annual rainfall of over 2200 mm. At higher elevations kava requires less water but even so it seems to need at least 1800 mm. This does not rule out its cultivation in locations with a very marked dry season, provided that the drought does not last too long, or irrigation is provided.

It is very important to plant at the beginning of the rainy season so that the plant can gain maximum benefit from rainfall during the critical months of growth. The first six months of growth are when kava is most susceptible to moisture stress.

  • · Kava is sensitive to drought stress and also to being too wet.
  • · Young plants should be watered well.
  • · Mulching will help reduce soil moisture loss. To avoid retaining too much moisture and encouraging disease do not use mulch during extended periods of rainfall.
  • · Shading young plants will reduce moisture stress.
  • · In windy areas use windbreaks to conserve moisture.

K. Pruning

Each node of the lateral branches sprouts roots and they root easily on contact with the soil. Allow this to continue without interference for at least the first 10 months of growth. At about one year the lateral branches should be trimmed just beyond the root growth from the last node and at the point where a new shoot has sprouted. The trimming of lateral roots encourages the development of the root system rather than the shoots which is preferable since the roots are the valuable harvested part of the plant.

L. Pest and disease management

Insects

Kava weevil (Elytroteinus subtruncatus) and other types of weevils that burrow into the rootstock and stem.

Control: change planting site

 

Ants (many species)

They can attack during the dry season and establish mealy bug colonies that feed on the bark and attract fungi and bacteria.

Control: irrigation

 

Slugs and snails (many species)

These pests can damage emerging shoots of young plants.

Control: apply snail bait

Nematodes

Nematodes are microscopic worm-like pests that can attack the roots of crops. Nematodes are found all over the Pacific, and 28 species have been identified in kava. Because there are so many kinds of nematodes farmers may be familiar with the symptoms of some species but not others. Nematodes are too small to be seen with the naked eye so the symptoms can be confused with diseases that have similar symptoms.

For example, the root knot nematode (Meloidogyne spp.) of which four have been found in kava, produces nodules or lumps on the roots which may grow up to 1 cm (° in) in diameter. The nematodes pierce the cell walls and absorb the contents, disturb the tissue and lay their eggs in it. As soon as they hatch out, the larvae move towards the healthy tissue to feed, which aggravates their harmful effect. When the nodules burst they are

quickly infected by a form of root rot, which can cause the death of the plant. If the nematode attack is severe the plant stops growing, wilts, and dies. Plants that have been attacked are very susceptible to falling over or lodging.

To help avoid nematodes use healthy planting material; avoid planting material taken from infected plants. The determining factor is the choice of a clean planting site where there are no harmful nematodes.

Root knot nematodes are controlled by intercropping with nematode-deterring crops such as turmeric (Curcuma longa) and marigold (Tagates sp.). To avoid the development of epidemic nematode populations, plants are usually spaced 2 m (6° ft) apart to allow intercropping. The weed problem that occurrs in widely spaced kava plants can be partly solved by establishing a cover crop such as sweet potatoes or unstaked yams.

A number of different plants can be infected by CMV, including the following

weeds: Ageratum conyzoides (goatweed); Commelina diffusa (wandering jew); Gomphrena globosa (globe amaranth); Lantana spp.; Physalis angulata (wild cape gooseberry); and Solanum nodiflorum (small flowered nightshade). To reduce the risk of CMV, weeds that carry CMV should be removed from the kava production site and surrounding areas.

Cultivated crops that can be infected include: Capsicum annum (peppers); Cucumis spp. (including rockmelon, honey dew, and cucumber); Cucurbita spp. (including pumpkin, squash and marrow); Lycopersicon esculentum (tomato); Musa sp. (banana); Nicotiana tabacum (tobacco); Passiflora edulis (passionfruit); Vigna spp. (including asparagus bean, black-eyed pea and cowpea); and Zea mays (corn). In an area known to have CMV, take care when choosing crops for intercropping; insects could transfer CMV from other infected plants to kava.

See the SPC Pest Advisory Leaflet on kava dieback for further information

Fungi

Twenty species of plant fungi have been identified on kava, but not many have been recorded as having any economic impact on production.

On recently cleared land, the remains of tree trunks and stumps may be infected with a fungus which lives in the soil and attacks the root system of kava plants. It then spreads from plants to plant by contact. The first symptoms of infection are wilting and rotting of leaf blades. The fungus lives as a parasite in the rootstock and root rot develops quickly, causing the plant to die within three weeks. This fungus has not been identified, but even when it is, it is unlikely that any very effective treatment will be found. It is best to be careful in the choice and maintenance of the site.

A kava plant affected by dieback.

Kava dieback

A major constraint to the intensification of cropping systems today is kava dieback disease, in which some of the stems rot from the apex or from the nodes to the stump.

Evidence from Vanuatu suggests that kava dieback is linked to low soil fertility and plants which are weak due to nutritional stress. Kava grown on well-drained fertile soils do not often develop kava dieback. To avoid kava dieback attention should be given to growing kava on fertile soils, and any infected plants should be removed. It seems clear that the spread of the disease is being facilitated by monoculture and that growers should be encouraged to intercrop below a tree canopy in other words to maintain traditional intercropping planting methods.

Recent studies (Davies, 1996) have shown that kava plants inoculated with the cucumber mosaic virus (CMV) developed symptoms of dieback. It appears that kava dieback may be caused by:

· CMV only;

· an interaction between CMV and another virus;

· two or more strains of CMV interacting; or

· an interaction between CMV and a non-viral pathogen.