Coconut Research Institute Repository

Perera, S.A.C.N.

QTL analysis in coconut via genome mapping. principles, requirements and prospects

Ranasinghe, C.S.

Illankoon, I.M.

Silva, L.R.S.

Premasiri, R.D.N.

Predeep, A.P.C.

Transitory Carbohydrate reserves in vegetative organs of coconut under different growth conditions and its relation with reproductive and vegetative growth of the palm

Jayawardana, J.K.J.P.

Sherief, A.K.

Influence of socio-psychological characteristics in adoption of organic farming practices in coconut based homesteads in humid tropics

Wijebandara, D.M.D.I.

Phosphorus status of major coconut growing soils of Sri Lanka on the performance of pueraria phaseoloides

Ekanayake, G.K.

Dassanayake, P.N.

Everard, J.M.D.T.

COCOS,2010,19: 41 -50 
Printed in Sri Lanka 
RESEARCH ARTICLE 
Varietal Classification of New Coconut (Cocos nucifera L.) Forms Identified 
from Southern Sri Lanka 
G K Ekanayake75- S A C N Perera', P N Dassanayake', J M D TEverard' 
'Coconut Research Institute of Sri Lanka 
'University of Sri Jayawardenepura, Sri Lanka 
'Current Address: Dhammissara National College, Nattandiya, Sri Lanka 
Author for correspondence: SA C NPerera Email: chandrikaperera2003@yahoo.com 
ABSTRACT 
Coconut in Sri Lanka is currently classified into 15 different coconut forms grouped under three varieties, 
namely Typica, Nana and Aurantiaca. Several new coconut morphotypes that were not represented in the 
previous classifications were identified during a recent coconut germplasm exploration mission in the Southern 
Province of Sri Lanka. The visual morphological features of several new coconut morphotypes (Ran pol, 
Bothal thembili, Juwan, Murusi, Dothalu and Thatin) were characterized with the objective of including them 
in the taxonomic classification of coconut in Sri Lanka Stature and breeding behaviour were the main features 
observed while stem morphology, root bole formation, crown size, nut morphology and bearing patterns, and 
other specific morphological features were recorded. The data provided morphological evidence to classify 
Ran pol, Juwan and Rath gon thembili as new forms of variety Typica; Green dwarf 'Murusi', Yellow dwarf 
'Murusi' and Brown dwarf 'Murusi' as forms of variety Nana; and Bothal thembili as a new form of variety 
Aurantiaca. The morphotypes, Thatin and Dothalu were identified as forms of variety Typica but the sample 
size was too small for confirmation. 
Key words: coconut, varietal classification, Sri Lanka. 
INTRODUCTION 
The classification of coconut has not been 
adequately standardized, and different authors 
in different countries use different terminology. 
Generally, coconut is classified, based on 
its stature and breeding behaviour, into two 
broad groups or types: tall (also termed typica) 
and dwarf (also termed nana). In addition, a 
few intermediate groups, sometimes referred 
to as semi-tails or semi-dwarfs have also 
been recognized. King coconut in Sri Lanka 
(Liyanage, 1958), Gangabondom in India 
(Menon and Pandalai, 1958) and Niu Leka Dwarf 
in Fiji (Powell, 1868; Bourdeix et al. 2005) are 
examples of such intermediate groups. 
The first systematic classification of coconut 
germplasm in Sri Lanka was reported in 1958 
42 
Ekanayake et. al. 
(Liyanage, 1958). This classification, based 
largely on stature and reproductive behaviour 
of the palm, recognizes three varieties, namely 
Typica (tall), Nana (dwarf) and Aurantiaca 
(intermediate). There are several morphotypes 
in each variety and these were termed as 'forms 
within varieties'. Liyanage's classification 
recognizes 13 forms within the three varieties. 
With the subsequent additions made by 
^Wickremarame (1984) and Perera et al. (1997) 
15 coconut forms have been recognized within 
the three varieties in Sri Lanka (Table 1). 
Variety Typica Nar. (tall) is the most abundant 
coconut variety in Sri Lanka and most coconut 
growing countries. It is tall in stature and naturally 
outbreeding. Typica forms usually take 5-6 years 
to flower and they produce flowers continuously. 
They are hardy palms that tolerate a wide range 
of environmental conditions. Typica, Navasi, 
Gon-thembili, Ran-thembili, Pora-pol, Bodiri, 
Kamandala and Dikiri are the different forms of 
the variety Typica (Table 1). The form Typica 
(Sri Lanka Tall), is grown on a commercial scale 
for production of endosperm, shell and fibre 
products. The other forms are found scattered in 
small numbers, mainly in home gardens. They 
are of little economic significance other than as 
candidates for breeding improved varieties. 
Variety Nana (Griff) Nar. (dwarf) is short 
in stature and naturally inbreeding. It flowers 
early in about 3-4 years from planting and is 
a seasonal bearer. Nana forms suffer adversely 
from drought, pests and diseases. Dwarf 
coconuts are not grown on a plantation scale 
but are extensively used in the production of 
coconut hybrids because of their short stature, 
precocity and profuse bearing ability. Green 
dwarf (pumila), yellow dwarf (eburnea,), red 
dwarf (regia) and brown dwarf braune (Perera 
et al. 1997) are the forms of the variety Nana 
(Table 1). 
Variety Aurantiaca Liy., which includes 
king coconut and similar forms, is intermediate 
in stature, predominantly inbreeding and 
late flowering. Flower production, which 
commences about 5 to 6 years after planting, 
is seasonal. The low tolerance to drought, pests 
and diseases restricts the areas in which king 
coconuts thrive. Tender king coconut, with its 
bright orange epicarp, and high sucrose, sweet 
nut water, is a very popular beverage coconut. 
Variety Aurantiaca has three forms, namely king 
coconut (thembili), rathran thembili and navasi-
thembili (Table i). 
Genetic variation in the germplasm pool 
provides material for crop improvement. Much of 
the diversity of coconut forms hitherto identified 
in Sri Lanka has already been extensively 
tested in breeding programmes. However, there 
is a need for more germplasm with diverse 
characteristics to meet the requirements of the 
coconut breeding programme. A survey, in the 
Southern Province of Sri Lanka, to explore new 
germplasm to enrich the Coconut Research 
Institute germplasm collection (Everard et al. 
2004), identified several new coconut phenotypes 
that merit detailed morphological assessment 
(Ekanayake et al. 2007). The aim of the current 
study was to morphologically differentiate the 
new forms identified in the Southern Province, 
and accordingly classify them under varieties. 
Varietal Classification of New Coconut (Cocoa nucifera L.) Forms Identified From Southern Sri Lanka 
43 
Table I: Varieties and forms of coconut found in Sri Lanka 
Common name (Variety/form) Specific morphological and reproductive features 
Sri Lanka Tall 
(TypicalTypica) 
Tall stature, allogamous, heterogeneous, flowers in 6 —7 
years, medium sized nuts, 20-25 nuts per bunch, 60-80 nuts 
per palm per year 
Gon Thembili 
(Typica/Gon thembili) 
Similar to Sri Lanka Tall. Ivory coloured nuts, petioles and 
inflorescences 
Nawasi 
(Typica/Nawasf) 
Similar to Sri Lanka Tall. Soft mesocarp - edible in the 
immature nut yields soft fibre when mature. 
Pora Pol 
(Typica/Pora pot) 
Similar to Sri Lanka Tall. Remarkably thick shelled nuts 
Ran Thembili 
(TypicalRan thembili) 
Similar to Sri Lanka Tall. Pink coloured mesocarp in 
immature fruit and a pink whorl under the perianth. Large 
nuts. 
Kamandala 
(Typica/Kamandala) 
Similar to Sri Lanka Tall. Large sized nuts (largest among 
local forms), and few nuts per bunch (2-5 nuts per bunch). 
Bodiri 
(Jypiai/Bodiri) 
Similar to Sri Lanka Tall. Small sized nuts and large 
number per bunch (30-100 nuts per bunch). Seasonal nut 
production. 
Dikiri 
(Typica/Difan) 
Similar to Sri Lanka Tall. Some nuts contain a jelly-like 
albumen/endosperm. 
King Coconut (Aurantiaca/King 
coconut) 
Intermediate stature, autogamous, homogeneous, fruits in 6-
7 years, seasonal flower production, medium sized nuts with 
orange epicarp and sweet nut water, 25-50 nuts per bunch. 
Nawasi Thembili 
(Aurantiaca/Nawasi thembili) 
Similar to King Coconut. Soft and edible mesocarp like 
Nawasi 
Rathran thembili 
(Aurantiaca/'Rathran thembili) 
Similar to King Coconut. Pink coloured mesocarp and a 
pink whorl under the perianth. 
Green dwarf 
(Nana/Green dwarf or pumila) 
Dwarf stature, autogamous, homogeneous, fruits in 3-4 
years, small sized nuts with green epicarp. low copra 
content, 80-150 nuts per palm per year 
Yellow dwarf 
(Nana/FeZ/ow dwarf or ebumea) 
Similar to Green dwarf. Nuts with yellow epicarp. 
Red dwarf 
(Nana/Red dwarf or regia) 
Similar to Green dwarf. Nuts with red epicarp. 
Brown dwarf 
(Nana/flrown dwarfor braune) 
Similar to Green dwarf. Nuts with a brown epicarp. 
M A T E R I A L S A N D M E T H O D S 
A survey was conducted in Galle area 
(Coordinates 603'0"N 80013 '0"E) (Figure 01) 
in the Southern Province of Sri Lanka. The 
surveyed lands were home gardens and small 
holdings where the traditional coconut varieties 
are planted, rather than the plantations where the 
commercial cultivars are grown. Much of the 
information regarding the different phenotypes 
and their locations were received from the 
coconut pickers in the area. 
Six new morphotypes of coconut, identified 
'in the survey, by their vernacular names, Ran 
pol, Bothal thembili, Juwan, Murusi, Dothalu 
44 
Ekanayake el. al. 
Table 2: Morphological characters and the traits scored for 
characterizing coconut morphotypes 
Character Traits scored 
Stem morphology stature (tall/dwarf) 
presence/absence of bole 
Crown morphology crown size (well spread/small) 
Fruit morphology fruit colour 
fruit shape 
fruit size 
Breeding behaviour self/cross pollinating nature 
seasonality 
Yield prolificacy 
and Thatin were assessed by studying the 
morphological parameters of the stem, crown and 
fruit, their reproductive and bearing behaviour 
as well as other specific morphological features. 
All these morphotypes were found in a few 
villages clustered around Unawatuna in Galle 
District of the Southern Province of Sri Lanka. 
Samples of 7 -10 palms each of Ran pol, Bothal 
thembili, Juwan and Murusi were assessed 
but only two palms of Thatin and one palm 
of Dothalu were available for this sludy. The 
morphological traits were scored over a period 
of 3 years to observe the temporal variation 
of the traits in each phenotype. Apart from the 
morphological traits specified in Table 2, other 
visually observable specific features of the new 
morphotypes were also recorded. 
RESULTS A N D D I S C U S S I O N 
Grouping the new phenorypes under coconut 
varieties 
The main morphological features used to 
group coconuts are the stature and breeding 
behaviour. In addition, the presence or absence 
of a bole, shape of the crown and regularity of 
bearing were taken into consideration. These 
features of the varieties Typica, Nana and 
Aurantiaca, and of the newly identified coconut 
morphotypes are presented in Table 3. Some 
features of the new morphotypes are illustrated 
in Figures 1-9. 
Varietal Classification of New Coconut (Cocos nucifera L.) Forms Identified From Southern Sri Lanka 
45 
9 9 
I I H i 
1 
Figure I: Ran pol crowns and nuts 
Figure 3: Juwan coconuts 
ll'feif 
Figure 5: Thatin coconut 
Figure 4: Murusi (Green) 
Figure 6: Dothalu coconut 
46 
Ekanayake et. al. 
Figure 9: Brown murusi 
Varietal Classification of New Coconut (Cocos nucifera L.) Forms Identified From Southern Sri Lanka 
47 
Table 3: Basic morphological descriptors utilized in coconut varietal 
classification in Sri Lanka and the corresponding features of the seven 
newly identified coconut morphotypes 
Variety/ 
Morphotype 
Stature Breeding 
behaviour 
Root 
bole 
Crown Bearing 
habit 
Typica tall cross pollinating present well spread year-round 
Nana dwarf self pollinating absent small intermittent 
Aurantiaca intermediate self pollinating present medium intermittent 
Ran pol tall cross pollinating present well spread year-round 
Bothal thembili intermediate self pollinating present medium intermittent 
Juwan tall cross pollinating present well spread year-round 
Murusi (green, 
yellow and 
brown) 
dwarf self pollinating absent small intermittent 
RathGon 
thembili 
tall cross pollinating present well spread . year-round 
Thatin tall cross pollinating present well spread year-round 
Dothalu tall cross pollinating present well spread intermittent 
The variety Typica essentially comprises tall 
and predominantly cross pollinating coconut 
palms. The data presented in Table 3 suggest that 
Ran pol, Juwan, Thatin, Dothalu and Rath Gon 
thembili can be grouped under variety Typica. 
Presence of a root bole is yet another prominent 
morphological feature defining tall coconuts and all 
root boles. Furthermore, these phenotypes exhibit 
well spread crowns and a year-round bearing 
pattern, which are also features characteristic of 
Typica. In regard to Thatin and Dothalu, as the 
sample size in the current study was inadequate, 
their grouping needs to be confirmed by studying 
more palms or by studying the selfed progeny of 
me above mentioned phenotypes display prominent the 2 morphotypes. 
48 
Bolhal thembili, with its intermediate stature, 
self pollinating breeding behaviour and the 
orange coloured fruit epicarp can be included in 
the variety Aurantiaca, which includes all king 
coconut types in Sri Lanka. The medium sized 
crown and intermittent nut production provide 
further evidence for this classification. 
The dwarf stature, predominantly self 
breeding nature, absence of a root bole, relatively 
small crown and the seasonal nut production 
provide evidence for considering Murusi as a 
Nana (dwarf) variety. 
Classification of the new coconut phenotypes 
as forms within varieties 
Distinct morphological features are used to 
classify different forms within a variety. The 
Ekanayake et. al. 
different forms within a variety possess the 
basic requirements to be included under that 
particular variety. In addition, each form has 
unique morphological features to distinguish it 
from all the other forms. Fruit colour, fruit size, 
fruit shape, petiole colour, mesocarp or endocarp 
softness and thickness, and the prolificacy of 
nut production are examples of traits used to 
distinguish forms within varieties. Table 4 
presents the specific morphological features of 
the new coconut phenotypes, identified from 
Southern Sri Lanka, which enable them to be 
regarded as forms within the three main varieties 
of coconut in Sri Lanka. Consequently, the new 
forms listed in Table 4 are not only different from 
each other, but also different from the forms 
identified by Liyanage (1958), Wickremaratne 
(1984) and Perera et al. (1997). 
Table 4: Specific morphological features of the new coconut types identified 
in Southern Sri Lanka and their classification as forms within 
varieties 
Vernacular name Specific morphological features 
(^Variety/form) 
Ran pol (Typica/Ran pot) Tall palms with stout fast growing stems. Very large round 
coconuts of mostly brown or less commonly green fruits. Plicata 
leaves (attached leaflets, especially in young fronds) 
Bothal thembili Intermediate palms producing orange, elongated coconuts of 
(Aurantiaca/Sof/ia/ unique shape. 
thembili) 
Juwan pol CTypicaJJuwan) Tall palms producing round small nuts. A high number (10-20) 
nuts per bunch. 
Murusi (Green) Dwarf palms producing green small coconuts which are rounder 
(None/Green 'Murusi") in shape than green dwarf nuts. Seasonal nut production. 
Murusi (Yellow) Dwarf palms producing yellow small coconuts which are rounder 
(Naaa/Yetlow Murusi"} in shape than yellow dwarf nuts. Intermittent nut production. 
Murusi (Brown) Dwarf palms producing brown coloured small coconuts which are 
(Nana/Brown 'Murusi') rounder than brown dwarf nuts. Seasonal nut production. 
RathCon Thembili Tall palms bearing orange coconuts. The petiole fronds and the 
CTypica/Rath Gon inflorescences also are of the same colour. 
thembili) 
Thatin CTypica/Thatin)* Tall palms producing elongated small coconuts with thick kernels 
and thin husks. 
Dothalu Tall palms producing green small elongated coconuts. A targe 
CTypica/Dothalu)* number of nuts per bunch (20-40) Very sweet nut water. Seasonal 
' nut production. 
* Sample size was inadequate to classify precisely 
49 
Varietal Classification of New Coconut (Cocos nucifera L.) Forms Identified From Southern Sri Lanka 
Table 5: Comparison of the nut size and kernel weight of the dwarf and 
Murusi forms 
Phenotype '•• Nut size (polar circumference 
cm) 
Kernel (g/nut) 
Green Murusi (54.1) 239.3 
Green dwarf (49.8) 135.8 
Brown Murusi (56.0) 210.6 
Brown dwarf (47.2) 185.7 
Yellow Murusi (53.9) 221.0 
Yellow dwarf (64.0) 272.3 
The green, yellow and brown phenotypes 
of 'Murusi' are classified within the relevant 
colour form of variety Nana (Table 4). This 
differentiation between Murusi and the relevant 
colour form of dwarf is mainly based on the 
differences in nut size and kernel weights of the 
dwarf and Murusi forms (Table 5). As shown 
in Table 5, Green and Brown Murusi produces 
larger and heavier nuts than the relevant dwarf 
forms while Yellow Murusi produces smaller 
and lighter nuts than Yellow dwarf. 
Many of the forms of coconut identified 
earlier (Kamandala, Bodiri, Pora pol, Dikiri 
etc.) were also naturally distributed in the 
Southern Province of Sri Lanka and testifies to 
the rich morphological diversity of coconuts in 
the area. The local community identifies the new 
coconut phenotypes by their vernacular names 
indicating that they have been grown or found 
naturally in the area over a long period of time 
and are not freaks or recent mutants. However, 
these traditional coconuts are endangered due 
to ongoing urbanization and coconut replanting 
programmes. Recognizing these coconut 
phenotypes as forms and their inclusion in 
the classification will draw attention to the 
possible existence of more traditional coconut 
phenotypes in Sri Lanka and the need for their 
conservation as germplasm accessions. These 
diverse materials are likely to carry valuable 
genes for exploitation in future coconut 
hybridization programmes for diverse uses in 
addition to being used directly for commercial 
purposes such as beverage coconuts and daily 
culinary requirements. 
A C K N O W L E D G E M E N T S 
The authors thank Dr. L. Perera, Head of 
the Genetics & Plant Breeding Division of the 
Coconut Research Institute of Sri Lanka for 
his constructive comments on the research and 
the manuscript. We gratefully acknowledge the 
financial assistance received from the Coconut 
Genetic Resources Network for the initial 
survey to identify farmers' varieties and from 
the Sri Lanka Coconut CESS Fund for the 
characterization and conservation of Southern 
Coconut germplasm. 
50 
Ekanayake 
REFERENCES 
Bourdeix, R. Santos, G. Labouisse, J. R and 
Baudouin, L. (2005). Useful definition 
of terms and nomenclature, In: Coconut 
Genetic Resources, P. Batugal, V. Ramanatha 
Rao and Jeffrey Oliver, ed., IPGRI, Rome, 
pp 9-10 
Ekanayake, G. K., Perera, S. A. C. N., 
Dassanayake, P. N. and Everard, J. M. D. T. 
(2007). Identification, characterization and 
conservation of new coconut phenotypes 
from Southern Sri Lanka. Proc. 12 t h Forestry 
and Environment Symp 2007. pp 76-77 
Everard, J. M. D. T. (2004). Report of the 
Genetics and Plant Breeding Division, 
Coconut Research Institute, Sri Lanka. 73-
77. 
Harries, H.C. (1978). The evolution, 
dissemination and classification of Cocos 
nucifera L. Bot. Rev., 44: 205-317 
Liyanage D. V. (1958). Varieties and forms of 
the coconut palm grown in Ceylon. Ceylon 
Coconut Quart., 9:1-10 
Manthriratna M. A. P. (1972). The performance 
of dwarfs (Cocos nucifera L. variety nana) 
as a plantation crop in Ceylon. Ceylon 
Coconut Quart., 23:92-99 
Menon, K P V. and Pandalai, K M. (1958). 
The coconut, A Monograph, Indian Central 
Coconut Committee, pp 86-102 
Perera, L. Peries, R R A. (1997). Brown dwarf: 
a recent addition to the varieties and forms 
of coconut palm grown in Sri Lanka. Cocos 
12: 82-84. 
Powell, T. (1868) On various Samoan plants 
and their vernacular names. Journal of 
Botany (London) 6: 278-285, 242-347^ 
255-370, Cited in Harries, H C. (1978). The 
evolution dissemination and classification 
of Cocos nucifera L., Bot. Rev., 44: 205-
317 
Wickremaratne, M. R. T. (1984). Report of 
the Genetics and Plant Breeding Division, 
Coconut Research Institute, Sri Lanka. 45. 


Varietal classification of New Coconut (Cocos nucifera L.) forms identified from southern Sri Lanka

Senarathne, S.H.S.

Gunathilake, H.A.J.

Weed management in mature coconut plantations in Sri Lanka

Waidyarathna, K.P.

Pradeep, A.P.C.

Meneripitiya, M.S.K.

Approach to screen coconut varieties for high temperature tolerance by in-vitro pollen germination

Perera, K.C.P.

COCOS, 2010,19: 51-56 
Printed in Sri Lanka 
RESEARCH ARTICLE 
Impact of Glyphosate on Weed Biomass and Growth of Coconut Seedlings 
in Nurseries 
S.H.S.Senarathne and KX.RPerera 
Coconut Research Institute, Lunuwila, Sri Lanka 
A B S T R A C T 
The effects of five different weed management systems on growth of coconut seedlings were evaluated to 
determine an economical and effective method for controlling weeds in coconut nurseries in the low country 
of the wet zone in Sri Lanka. The treatments comprised of manual weeding (T,), application of glyphosate at 
1.44 kg ai/ha fT,), 1.08 kg ai/ha (T,), 0.72 kg ai/ha (T4) and 0.36 kg ai/ha (Ts) applied at three-month intervals. 
Treatments 1 and 2 significantly reduced the weed biomass when compared to other treatmetns. The growth 
of coconut seedlings (in terms of height and girth) increased significantly (P<0.05) with the application of 
glyphosate at 1.08 kg ai/ha (T3) at the end of the nursery growth period. At the higher concentration (1.44 
kg ai/ha) the growth of seedlings was reduced at the latter part of the experiment. Therefore, the most cost-
effective treatment of controlling weeds in the study was to apply glyphosate at the rate of 1.08 kg ai/ha (31 of 
commercial mixture/ha). Manual weeding was neither effective no economical. 
Key words: coconut, seedling, monocotyledonous weed, glyphosate 
INTRODUCTION 
Coconut (Cocos nucifera L.) is by far the 
most extensively cultivated major plantation 
crop in Sri Lanka (Liyanage and Liyanage, 
1989). It is distributed in approximately 0.444 
mn ha of land throughout the island (Central 
Bank, 2002). To establish and maintain proper 
plantation, a high quality coconut seedling 
are an essential perquisite. Annually more 
tiian 2 mn coconut seedlings are issued to the 
growers for their replanting program (Plantation 
Sector Statistical Book, 2002). Therefore, to 
produce high quality seedlings much attention 
needs to be paid during the nursery period. 
Coconut seedlings are raised in nurseries prior 
to field planting. Proper care and maintenance 
of seedbeds facilitate the selection of early 
germinating vigorous seedlings (Peries and 
Everard, 1993). The inheritance studies carried 
out by Liyanage and Abeywardana (1957) have 
showed that seedling vigor is correlated with 
adult palm characters such as early flowering 
and high nut and copra yield. In the nursery, 
apart from irrigation, weeding is very important 
though expensive. Good weed management 
can minimize economic losses as reported by 
Suryaningtyas (1997) and Wibawa (1997). 
Seedbeds should be weed free; otherwise 
weeds would compete with coconut seedlings 
for nutrient and moisture. Each weed species 
has different effect on growth of plants (Eaton 
52 
Senarathne 
et al., 1976). However, information on growth 
reduction of seedlings due to weed competition 
in the coconut nurseries in Sri Lanka is not 
available. 
The most popular method of weeding in 
coconut nurseries is hand weeding, which is 
labor intensive and time consuming (Remison 
& Mgbeze, 1987). Hand weeding has not been 
effective, especially for weeds with underground 
storage organs (Pethiyagoda, 1980). Chemical 
weeding is also adpted by nursery growers. 
Glyphosate has a systemic action and it is very 
effective to control grass weeds in coconut 
nurseries such as Imperata cylindrica, Cynodon 
dactylon, Panicum maximum and Cyperus 
rotundus. These are the common weeds in coconut 
nurseries of the wet zone. In Sri Lanka Cyperus 
rotundus is one of the major weed species found 
in wet zone coconut nurseries (Gunasekara and 
Fernando, 1994). Glyphosate is a widely used, 
non-selective, foliage applied herbicide which 
is known to be highly toxic to Panicum repens 
(Manipura & Somarathne, 1974). Glyphosate 
is also a commonly used herbicide in mature 
coconut plantations because it is non-selective 
and affects a wide range of monocotyledonous 
and dicotyledonous annuals, biennials and 
perennials (Boyall, 1998). However, glyphosate 
can be harmful to both weeds as well as coconut 
seedlings. Hence the objective of this study 
was to identify most economical and effective 
method of weed control in coconut nurseries. 
MATERIALS AND METHODS 
The experiment was carried out during 
October 2002 to June 2003 in a coconut nursery 
located at Wennoxuwa in the Low Country Wet 
Zone of North-Western province of Sri Lanka. 
The average day temperature at the site was 
around 27C0 and rainfall was uneven with dry 
spells. All the coconut seed nut were selected 
from high yielding mother palms. Seed nuts 
were laid in the nursery beds spaced at 45cm 
between rows and 15cm within rows in October 
2002. Each experiment plot measured 2.5m x 
3 .m containing 40 seed nuts within a nursery bed. 
The experiment was conducted in Randomized 
Complete Block Design with three replicates. 
The treatments were Manual weeding (T,), 
Glyphosate application at 1.44 kg ai/ha (J2), 
1.08 kg ai/ha (T3), 0.72 kg ai/ha (TJ; 0.36 kg ai/ 
ha (T5) and T6 - No weed control. Glyphosate 
was applied uniformly over the plot using a 
hand sprayer at three months intervals starting 
from October 2002 and ending in May 2003. 
Weed biomass: The weed biomass was 
collected every month form 0.25m x 0.25m 
quadrates from four random points per plot. 
The weeds were separated into species and dried 
to constant weight at 80 0C for five days from 
October 2002 to May 2003. 
Coconut seedling girth and height: Ten 
coconut seedlings were selected randomly and 
plant height and stem girth (base of the seedling) 
were measured. 
Data analysis was conducted using Analysis 
of Variance (ANOVA) using Statistical software 
and the significance was tested using the Least 
Significant Differences (LSD) (P=0.05) (SAS 
Institute 1999). 
RESULTS AND DISCUSSION 
Effect of different glyphosate 
concentrations on weed biomass: Major weed 
53 
Impact of glyphosate on weed biomass and growth of coconut seedlings in nurseries 
species in this site were Imperata cylindrica, 
Panicum repens. Cynodon dactylon, Chloris 
barbata, Mimosa pudica, Urena lobata, 
Croton hirtus, Allmania nodiflora, Mitracarpus 
villosus, Tephrosia purpurea, Vernonia cinerea, 
Tridax procumbens, Sida acuta, Scoparia 
dulisis, Stachytarpheta jamaicensis and Hyptis 
suaveolens. Weed biomass was lowest in plots 
which received 1.44 kg ai/ha and 1.08 kg 
ai/ha of glyphosate respectively (Fig. 1). At the 
lowest concentration of glyphosate (0.36 kg ai/ 
ha) (Tj) and in manual weeding (T () treatments 
were not sufficient to suppress the weed 
population satisfactorily. However, Glyphosate 
application at 1.44 kg ai/ha (T2), 1.08 kg ai/ha 
(T,) and 0.72 kg ai/ha (TJ were found to be 
parts could not be destroyed. Therefore, weeds 
appeared within a very short period of time. 
However, dicotyledonous weeds were very easy 
to control manually. Boyall (1979) showed 
that when glyphosate was applied; it is trans­
located to underground rhizomes and destroys 
all-visible buds. Therefore, the best method 
of eradicating monocotyledonous weeds is the 
application of glyphosate. Seed bank of weeds 
in the soil creates new weed populations, which 
predominantly comprise of dicotyledonous 
weeds. 
Effect of glyphosate on coconut seedling 
growth: Glyphosate 1.08 kg ai/ha (3 1/ha) 
significantly increased (P<0.05) the height and 
girth of seedlings compared to other treatments 
Thu • (mentha) 
- H m d — « H n q m QNphOMla 1.441c (MM Q l y p M a u a 1 M h) 
, M OlyphMMo 0.72 I g alf ltt u QlyplMMaM I M H) *1A<* 
Figure 1: Effect of treatments on weed biomass (g m2) 
effective in reducing both monocotyledonous (Tables 1 & 2). This increase started from the 
and dicotyledonous weeds? latter part of the nursery growth period with the 
, , reduced competition of weeds for.soil moisture 
When manual weeding, fast re-growth, 
and nutrients. 
especially monocotyledonous weeds was 
observed, as under ground vegetative plant 
Senarathne 
Table 1: Effect of weed control treatments on collar girth (cm) of 
coconut seedlings from October 2002 to May 2003 
Time (month) 
Treatments Feb Mar April May June 
2003 2003 2003 2003 2003 
Tp Manual weeding 5.28 7.27 9.08 11.15 13.10 
T r Glyphosate 1.44kg ai/ha 6.01 7.65 9.30 12.25 12.70 
T 3 - Glyphosate 1.08kg ai/ha 6.21 7.64 9.36 12.50 14.83 
T«- Glyphosate 0.72kg ai/ha • 5.98 7.78 9.60 12.25 13.80 
T5- Glyphosate 0.36kg ai/ha 5.82 7.22 8.80 10.94 13.09 
T e - Unweeded control 6.02 7.32 8.02 9.96 12.30 
LSD (P=0.05) 
- - 0.93 0.79 1.80 
CV% 
- -
5.69 3.81 4.37 
Table 2: Effects of weed control treatments on height (cm) of 
coconut seedlings from October 2002 to May 2003 
Time (month) 
Treatments Feb Mar April May June 
2003 2003 2003 2003 2003 
Ti- Manual weeding 54 63 82 97 107 
T r Glyphosate 1.44kg ai/ha 60 68 92 112 118 
T r Glyphosate 1.08kg ai/ha 63 69 87 109 125 
T +- Glyphosate 0.72kg ai/ha 55 65 87 107 115 
Tj- Glyphosate 0.36kg ai/ha 50 60 81 102 109 
Tj- Unweeded control 47 58 78 99 109 
LSD (Pa0.05) 6 7 7 8 
CV% 
- 4.5 4.7 3.6 3.9 
At the end of the experiment coconut 
seedlings in the T 3 treatment (Glyphosate at 
1.08 kg a.i./ha) were tallest followed by the T 2 
(Glyphosate at 1.44 kg a.i./ha) treatment. The 
highest collar girth increment was found in T 3 
(Glyphosate at 1.08 kg a.i./ha) while the second 
highest increment was found in T 4 (Glyphosate 
at 0.72 kg a.i./ha) treatment. This indicates that 
T 2 (Glyphosate at 1.44 kg a.i./ha) treatment is 
more effective in reducing the weed population 
with no effect on coconut seedling growth. 
Some yellow patches also appeared on leaves 
of seedlings sprayed with 1.44 kg ai/ha (T 2) and 
1.08 kg ai/ha glyphosate (T 3). It was noted that 
manual weeding did not result in any significant 
increase in growth parameters of the coconut 
seedlings compared to those in unweeded 
plots. There were no significant differences 
between seedlings in control, manual weeded 
and low concentration of glyphosate used (0.72 
kg ai/ha and 0.36 kg ai/ha) plots. The highest 
growth rate of coconut seedlings was observed 
in the T 3 treatment (Glyphosate at 1.08 kg ai/ 
ha) (Tables 1& 2). The rates of seedling height 
and girth increase were 16.4 cm and 2.2 cm per 
month respectively in T 3. 
Cost benefit analysis of different weed control 
method 
The costs of different weed control methods 
are given in the Table 3. 
Impact of glyphosate on weed biomass and growth of coconut seedlings in nurseries 
55 
Table 3 : Cost analysis of different weed control treatments. 
Treatments 
Frequency of 
treatment 
application 
during the 
nnrserr period 
Weeding cost per 
1000 coconut 
seedlings in o n 
application 
Total weeding cost 
per 1000 coconut 
seedlings during the 
nursery period 
Ti-Manual weeding 4 1000.00 4000.00 
Tr Glyphosate 1.44kg ai/ha 3 66.00 198.00 
T r Glyphosate 1.08kg ai/ha 3 60.00 180.00 
T«- Glyphosate 0.72kg ai/ha 3 52.00 156.00 
li- Glyphosate 036kg ai/ha 3 44.00 132.00 
A v t i i j c pnee of c o m o e r a a l prodacl of fiypbeatic SL R* 400 max 
A v n g s labor vtgK SL H i 500/ ta iaday 
US IS . Sri Lankan (SL) IU I U 
Treatments with glyphosate at 1.44 kg ai/ 
ha and 1.08 kg ai/ha produced the lowest weed 
biomass, but the most cost-effective method 
of controlling weeds in the study was to apply 
glyphosate at the rate of 1.08 kg ai/ha (3 1 
commercial mixture per ha). Manual weeding 
was the most expensive. The low concentrations 
of glyphosate treatments such as T 4 and T ; were 
less expensive but they were not effective in 
controlling weeds. 
CONCLUSION 
Application of glyphosate at 1.08 kg ai/ 
ha gives the most cost effective weed control 
method to produce good quality seedlings in 
coconut nurseries. Lower concentrations did not 
control weeds effectively in coconut nurseries. 
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