Coconut Research Institute Repository

Jayasekara, C.

Ranasinghe, C.S.

Wimalasekera, R.

Improving coconut palm characters for increased productivity

Two methodologies are pooposed to determine the most efficient plot size for tree crops using data from experiments based on randomized complete block designs. Both methods can be generalized for data from any balanced design. The merits and demerits of these methods are discussed. The methods are illustrated using the data sets of long-term field ecperiments at the Coconut Research Institute, Sri Lanka. The results show that efficient plot size in field experiments for coconut for a wide range of agroecological regions is four or six palms

Peiris, T.S.G.

Thattil, R.O.

COCOS (1997), 12,44 - 53 
Printed in Sri Lanka. 
ALTERNATIVE METHODS TO DETERMINE PLOT SIZES FOR 
TREE CROPS: 
A CASE STUDY FROM COCONUT DATA 
T S G Peiris 1 and R O Thattil2 
/ Coconut Research Institute, Lunuwila, Sri Lanka 
2 Department of Crop Science, Peradeniya University, 
Peradeniya, Sri Lanka 
SUMMARY 
T w o methodologies are proposed to determine the most efficient plot 
size for tree crops using data from exper iments based on randomized c o m ­
plete block designs . Both methods can be general ized for data from any 
balanced design. T h e meri ts and demerits of these methods are discussed. 
The me thods are illustrated using the data sets of long-term field exper i ­
ments at the Coconut Research Institute, Sri Lanka. The results show that 
efficient plot size in field exper iments for coconut for a wide range of agro-
ecological regions is four or six palms. 
INTRODUCTION 
In field exper iments the efficient testing of the treatment effects d e ­
pends upon the exper imental precision. One way of increasing efficiency is 
to use op t imum plot and block sizes to maximize the information obtained 
for each rupee of money spent. The size and shape of plots as well as b locks 
are usually de termined by evaluating uniformity trials over a long period. 
T h e s e trials are expens ive to perform and need large extent of land. Conse ­
quent ly the op t imum plot size has not been thoroughly studied for many tree 
c rops , part icularly for coconut . 
T h e Coconut Research Institute of Sri Lanka (CRISL) conducts , an­
nually, on the average , 1 0 - 1 5 long-term field exper iments in different fields 
44 
of specialty to improve coconut cultivation. Consider ing the nature of the 
exper iments at the C R I S L and the yield variation be tween pa lms , r andom­
ized comple te b lock designs have been commonly used. 
Pieris and Salgado (1937) suggested 1 6 - 1 8 pa lms per plot which 
occupies nearly 0.1 ha per plot. This is not economical in m a n y c i rcum­
stances . O n the assumpt ion of biennial bearing of tree crops Abeywardena 
(1964) suggested a m i n i m u m plot size of six pa lms to reduce the biennial 
fluctuation. Abeys inghe (1986) r ecommended that a plot size of four pa lms 
could b e used for complete ly randomized design (CRD) exper iments if the 
t w o year pooled pre-experimental yield can be used as a covariate in the 
analysis . Th i s approach is not flexible as data for the previous two years for 
the exper imenta l site are not a lways available. These studies were based on 
single sets of data. Further, as yield of coconut fluctuates with changes in 
c l imate and weather the investigation of plot sizes for different agro-ecologi­
cal regions of Sri Lanka is necessary. 
Pearce (1978) stated that, " the resident biometrician should look back 
ove r comple ted exper iments to see how things have turned out , not from the 
point of v iew of agronomic results but of biometrical efficacy". 
T w o methods are proposed here to decide on the mos t efficient plot 
size for any tree c rop using the past data from any balanced design exper i ­
ment . T h e me thods are illustrated using two sets of coconut data conducted 
at two different agro-ecological ' regions of Sri Lanka by the Coconut R e ­
search Insti tute (CRI) . 
METHODOLOGYI 
Let Y.. k b e the response variable (yield) of the k* (k=l ,2 , . . .n) p a l m 
(experimental 1 unit) in the i* ( i= l b) block of the j * ( j= l , t) t reatment 
where n is the number of pa lms per plot (that is, plot size). In a randomized 
comple te b lock design ( R C B D ) the number of t reatments are equal to the 
n u m b e r of plots within a block and the treatments are randomly al located 
a m o n g plot wi thin a block. Y..k can b e written as ; 
Y„ k = n + Ri + T . + e i. + p . j k (1) 
Where p\ = effect of the i* block, T. = effect of the j * t reatment , e y = 
r a n d o m variabili ty (experimental error) , p„ k = r andom variability (pa lm to 
p a l m within plots) and u, is the overall effect. £.. can be assumed to be inde-
45 
pendent and distributed as N(0,a2e), p.jk can be assumed to be independent 
and distributed asN(0,o2p). the general analysis of variance table (ANOVA) 
of the model (1) is given in Table 1. 
Table 1. General analysis of variance table under model (1) 
source of 
variation 
degrees of 
freedom 
sums of 
squares 
mean 
squares 
Between blocks b-1 SSB MSB 
Between treatments t-1 SST MST 
Experimental error (b-D(t-l) SSEE MSEE 
Plot total bt-1 SSPT MSPT 
Palms within plots 
(Sub-sampling error) 
(n - l)bt SSSE MSSE 
Total nbt-1 SSTT 
SSPT = (SSB+SST+SSEE) and SSTT = (SSPT+SSSE). If 
Y.. •= Z, Z.ZkY..k/ btn then the coefficient of variation for the experiment, CV 
is given by, 
CV =N 
MSEE 
* 100 (2) 
The method involves calculating the coefficient of variation for new 
plots of different sizes and observe at which 'point' the CV stabilized. As 
Y.jk's have treatment effect and block effect, plot sizes are chosen from the 
palms within a plot. To choose identical plot shape the palms within a plot 
are numbered in the same sequence from one to n (see Appendix A). For 
each plot size and plot shape the MSEE and Y... are computed. In choosing 
plots the following steps can be adopted. 
46 
1. All palms numbered 1 in each plot are used to calculate CV of plot 
size one.This is repeated separately for all palms within plot numbe­
red from 2 to n. The average of these n CV's is taken as the CV of 
plot size of one. 
2. The number of palms per plot is now increased to 2, by selecting 
palm numbers 1 and 2 from each plot to form plot size of two. All the 
possible combinations of each plot size of two are selected from each 
of the original plots such that if a particular pair of numbers is 
selected from plot 1, then the same numbers are selected from the 
remaining plots. Thus there aren(n-l)/2 separate analysis for*CV 
for plot size of two. The average of these n(n-l)/2 CV's is taken to 
represent theCVof plots of size two. 
3. The above procedure is repeated for plots of size 3 to n. 
4. The average CV's are plotted against the plot size. The plot size at 
which CV values stabilized is taken as the most efficient plot size. 
METHODOLOGY II 
In a typical uniformity trial the model is 
Y. = !* + £. ..(3). 
Therefore from the observed values Y..k the treatment effect and the 
block effect are removed to make the model (1) comparable to model (3). 
When those effects are removed the ensuing yields can be treated as if they 
come from a uniformity trial. If X.jk is the~yield after removing the treatment 
and block effects then, 
X i jk = Y i j k - ( n + P i + T . ) 
- = Y y k -Y . . , (Y -Y...)-(Y.-Y...) 
= Y y k - Y . - Y . + Y (4) 
where Y. = 1.2 k Yijk/tn, Y. = £ I k Y^/bns, and Y...= I. Z. I k Yijk/btn. 
The X..k's canvbe'considered as Y. (i= 1,2,3, btn) and can be analyzed 
using Fairfield Smith's technique (Smith, 1938). This technique has been 
widely used to find the plot sizes for different crops using data from unifor­
mity trials. The Fairfield Smith's techniques is briefly explained here. 
4 7 
Different plot sizes from 1 to n are selected from the initial field plan. 
Pa lms are selected across the rows and columns so that the shape of plots are 
rectangular or square. When there are Nx plots of size x (1 < x < n) with yield 
Y per plot then the coefficient of variadon C V is 
C V
 s = i—— * 100 (5) 
Y 
X 
W h e r e V x is the variance of plots of size x and Y x is the mean of plots of size 
x. T h u s by calculat ing CV^ for different plot sizes the most efficient plot 
size is obta ined from the plot of C V x vs x. 
The shape of the plots and blocks is usually decided by the nature of 
the exper iment and the area of the land available. However , rectangular and 
square plots are generally preferable for tree crops. Method II can be used to 
s tudy the plot shape and block, but method I has some limitations to tackle 
this p rob lem as plots are selected within the pre-defined plot. Another disad­
vantage of method I is that the max imum number of plot size has to be re­
stricted to the initial plot size of the experiment. 
Bo th methods showed that the op t imum plot size is not affected by 
the number of plots . In R C B D number of plots are equal to the number of 
t reatments irrespective of the plot size. In our analyses the effect of the 
guard rows were not considered and hence the cost associated with the pa lms 
in the guard rows does not arise. Guards rows are generally not recom­
m e n d e d for the experiments in coconut palms except intercropping trials 
because there is no fertilizer movement between pa lms. But, the guard rows 
can be considered if required under both methods. 
APPLICATION OF THE TWO METHODS 
Secondary Data 
The yield data (1985-87) for this study were obtained from two long-
te rm field exper iments conducted in low country region of the intermediate 
zone ( 7 5 % expectancy of annual rainfall > 1800mm) and dry zone ( 7 5 % 
expectancy of annual rainfall > 1500mm) by CRISL. The design of both 
exper iments was R C B D . 
Exper iment 1 was to study the effect of incorporating coir dust on the 
physical condi t ion of the soil structure. It had five treatments and five blocks 
48 
and each block consists of five plots of eight palms. Experiment 2 was to 
compare the effects of three frequencies of ploughing and two depths with an 
unploughed control treatment on a sandy soil. It had seven treatments and 
four blocks and each block consists of seven plots of nine palms. 
The field plan of each experiment is shown in Appendix A. Further 
details can be found in CRI (198S). The two methods were applied to each 
set of data on yearly basis. 
Use of Method I 
As explained above the possible rectangular and square shape plots 
were selected. The plot size was varied from one to eight in data set 1 and 
from one to nine in data.set 2. The analyses was carried out for yearly data 
and the mean CV was taken for a given plot size. The variation of mean CV 
for different plot sizes, of the data sets 1 & 2 are shown in Figures 1 .a and 1 .b 
respectively. 
Figure l.(a) clearly indicated that CV decreased sharply when the 
plot size increased from one to four in all years, but after that there was no 
appreciable decrease. After the plot size of six the decrease of CV is negli­
gible. Similar trend can be seen in Figure 1 .(b). Thus the efficient plot size 
can be taken as four or six palms without any covariates. 
Use of Method II 1 
The treatment and block effects were removed from individual palm 
yield on yearly basis. The experiment 1 has 10 rows of 20 palms and 20 
columns of 10 palms and experiment 2 has 12 rows of 21 palms and 21 
columns of 12 palms (see Appendix A). Non overlapping plots of size one to 
ten were selected along each row and each column! In selecting plots along 
rows (or columns) a few palms at the end had to be neglected when the 
remaining palms were not divisible by the plot size. The mean CV for a 
given plot size over different combinations was computed. 
The plots in Figure 2 also have the similar trend as in Figure 1 indi­
cating that 4-6 palms per plot are sufficient in. both locations with respect to 
coefficient of variation. It also indicates that CV decreased rapidly for every 
single palm increase from one to six. 
49 
Table 2 shows the computed values of CV's under two methods . It can be 
seen that the C V is extremely high for plot size of one palm. 
Table 2 . T h e computed values of C V for the two sets of data under the 
two methods . 
M e t h o d Plot data set 1 data set 2 
1985 1986 1987 1985 1986 1987 
1 31.4 30.6 34.7 27.8 28 .4 31.7 
2 20.5 17.7 22.3 12.4 14.2 14.0 
3 15.7 12.1 19.1 10.6 12.1 12.4 
4 14.8 10.4 15.5 10.0 11.7 11.5 
5 13.8 9.9 15.2 9.9 11.6 11.3 
6 13.4 9.7 14.7 9.7 11.4 11.2 
7 13.2 9.6 14.2 9.6 10.6 10.8 
8 12.9 9.3 13.9 9.4 10.3 10.7 
9 - - - 9.3 10.1 10.6 
1 30.0 25.8 30.1 25.4 25.8 27.4 
2 21.1 18.2 21.8 18.2 18.9 20.1 
3 17.7 15.3 18.2 15.0 16.2 18.0 
4 14.1 12.5 15.7 13.3 13.9 16.1 
5 13.2 11.7 14.8 11.7 12.6 13.8 
6 12.0 11.0 13.4 10.8 11.8 13.6 
7 11.3 10.6 12.8 10.5 11.4 13.2 
8 10.4 10.3 12.2 9.9 10.9 12.7 
9 10.3 10.1 11.8 9.6- 10.8 12.6 
10 10.2 9.9 11.7 9.5 10.7 12.3 
C O N C L U S I O N S 
T h e s tudy showed that the two methods proposed in this paper are 
sui table to determine the op t imum plot size for any tree crop. Thus conduct ­
ing uniformity trials can be avoided if secondary data sets of the des igned 
exper iments are available. Al though the examples ci ted in this paper were 
based on actual data from the R C B D , these methods can be easily extended 
for data from any type of balanced design. 
M e t h o d II has more advantages than method I. The methodology II 
5 0 
3 4 6 6 
Plot size (number of palms) 
3 4 S 6 7 
Plot size (number of palms) 
Figure 1. Relation of coefficient of variation (CV%) to 
plot size based on Method I using (a) data set 1 
and (b) data set 2 
5 1 
5 -
0 H 1 1 1 1 1 1 1 1 
1 2 3 4 5 6 7 8 9 10 
Plot size (number of palms) 
5 -
"0 T 1 1 1 1 1 1 1 1 
1 2 3 4 5 6 7 8 9 10 
Plot size (number of palms) 
Figure 2. Relation of coefficient of variation (CV%) to 
plot size based on Method II using (a) data set 1 
and (b) data set 2. 
5 2 
can be used to determine the effective plot shape and block shape as well, 
though the standard practice in tree crop trials is rectangular plots. As the 
uniformity trial data are very useful in agricultural research the benefits of 
such data can be obtained,by removing the appropriate effects from the sec­
ondary data using the model (4). The data from a typical uniformity trial 
strictly speaking is valid only in the specific location in which the trail is 
conducted. Thus when the past data are available uniformity trials need not 
be repeated for different locations. 
Since the data used in this study were in different agro-ecological 
regions, the plot size of four or six palms is recommended in field experi­
ments for coconut irrespective of the location without the use of pre-data as 
covariate. Based on the pattern of CV in Figures 1 and 2, single palm plots 
are not recommended in any field experiments for coconut. 
ACKNOWLEDGEMENTS 
We are grateful to the Heads of Soils & Plant Nutrition and Agronomy 
Divisions of the CRISL, for permitting the use their experimental data. 
REFERENCES 
AbeysingheThilak(1986). Calibration of experiments on perennial crops 
using covariance analysis: the case of coconut. Experimental 
Agriculture, 22 : 353 - 361; 
Abeywardena, V. (1962). Studies on biennial bearing tendency in coconut -
A minimum plot size for coconut. Ceylon Coconut Quarterly, 15:109 -14 
CRI (1985). Report of the Coconut Research Institute for 1985 (Ed. R 
Mahindapala), Lunuwila, Sri Lanka. 
Pearce, S. C. (1983). The Agricultural field experiment - A statistical examination 
of theory and practice. John Willey and Sons Ltd, New York, 293 pp. 
Peiris, W. V. D. andSalgado, M. L. M. (1937). Experimental error in field 
experiments with coconut. Trop. Agriculture, Trinidad, 89:75-85 
Smith, H.F. (1938). An empirical law describing heterogeneity in the yields 
of agricultural crops. J. of Agric. Science, Cambridge, 28:1-23. 
5 3 


Alternative methods to determine plot sizes for tree crops. a case study from coconut data

Tennakoon, N.A.

Effect of application of heavy metal contaminated sewage sludgeon long-term nutrient cycling in coniferous forest soils

Liyanage, M.de.S.

Organic manures: A source of micronutrients

Vidhana Arachchi, L.P.

Yapa, P.A.J.

Mapa, R.B.

Somapala, H.

Effect of soil physical properties on the nutrient in flow in coconut (Cocos nucifera L) seedlings

Allan, E.J.

Coventry, E

Wickramananda, I.R.

Mordue(Luntz), A.J.

Screening of neem plant extracts for biological activity

Vidhanaarachchi, V.R.M.

Weerakoon, L.K.

COCOS (1997), 12,39 - 43 
Printed in Sri Lanka 
C A L L U S I N D U C T I O N A N D D I R E C T S H O O T 
F O R M A T I O N I N IN VITRO C U L T U R E D I M M A T U R E 
I N F L O R E S C E N C E T I S S U E S O F C O C O N U T 
V R M V i d h a n a A r a c h c h i a n d L K W e e r a k o o n 
Coconut Research Institute, Lunuwila, Sri Lanka 
A B S T R A C T 
Clonal propagation of elite palms is a promising possibility for pro­
ducing uniform planting material and improving productivity in coconut lands. 
In the absence of a natural vegetative propagation method, in vitro culture 
remains the only approach for vegetative multiplication of coconut. 
Immature inflorescence material has shown to be a promising source 
of explants for coconut tissue culture. In the present study, four different 
culture media (medium 72; modified Eeuwens Y3 medium; coconut anther 
culture med im; modified Blake ' s medium) were evaluated for callus induc­
tion in floral explants : Immature inflorescences were collected non-destruc-
tively from 12 year old Sri Lanka-tall coconut palms and rachilla segments 
obtained from these inflorescences were cultured on above media . 
Out of the four culture media tested, callus production was observed 
only in the explants cultured on medium 72. In this med ium (which con­
tained 24 U .M 2,4-dichlorophenoxyacetic acid and 0 . 2 5 % activated char­
coal) , about 3 0 % of the floral explants produced compact , highly embryo-
genie calli . Direct regeneration of shoots from floral pr imordia occurred at & 
very low frequency in the modified Eeuwens Y 3 medium which contained 
200 u M 2,4-dichlorophenoxyacetic acid and 0 .2% activated charcoal . N o 
cal logenesis or direct organogenesis were observed in the floral explants 
cultured on the other two culture media tested. 
I N T R O D U C T I O N 
Coconut pa lms raised from seeds show a wide variation in the field 
due to their highly heterozygous nature. Vegetative multiplication of elite 
pa lms is a promis ing poss ib i l i ty for producing uniform planting material of 
3 9 
high quality. This would not only improve the productivity in coconut lands 
but a lso p roduce uniform parent material for breeding programmes . In vitro 
cul ture is the only channel open for intensive vegetat ive propagat ion of co­
conu t and the development of a reliable in vitro c loning technique would 
a lso pave the way to genetic transformation of coconut by transfer of foreign 
genes that confer desirable characters. 
Recen t studies on immature inflorescence culture o f coconut have 
indicated that plant regenerat ion through somatic embryogenesis is possible 
bu t the technique has not yet been mastered (Verdeil et. al. 1994; Hornung , 
1995). A t the Coconut Research Institute, of Sri Lanka, work on clonal propa­
g a t i o n h a s been done ma in ly wi th immatu re e m b r y o (Karunara tne and 
Per iyapperuma, 1989) and leaf explants (Karunaratne et at 1991) and very 
little work has been done on inflorescence culture. Therefore, the present 
s tudy was under taken to assess the suitability of four different culture media 
for cal lus induct ion in immature inflorescence explants with a v iew to de ­
velop a rel iable protocol for clonal propagat ion of coconut . 
M a t e r i a l s a n d m e t h o d s 
Immatu re inflorescences of 8 -10 c m outer spathe length were o b ­
ta ined non-destruct ively (Rillo, 1989) from 12 year old Sri Lanka-tal l coco­
nut pa lms . T h e inflorescences were surface sterilized for 15 minutes in 3 % 
ca lc ium hypochlor i te solution followed by thorough rinsing with sterile dis­
tilled water. Then the outer a n d inner spathes were removed under aseptic 
condi t ions . T h e top and basal portions of the inflorescence were discarded 
and only the middle port ion of the inflorescence ( a b o u t 3 c m in l e n g t h ) was 
used for culturing. Rachil la was cut into 1-1.5 m m long sections and cul­
tured into sc rew capped vials containing 15 ml of culture med ium. The fol­
lowing cul ture media were used in this study. 
1. M e d i u m 72 formulated by Karunaratne and Per iyapperuma (1989) 
containing 24 u M 2,4-dichlorophenoxyacetic acid ( 2 , 4 - D ) a n d 
o . 2 5 % activated charcoal . 
2. Modif ied Eeuwens Y3 med ium described by Verdeil et. al. (1994) 
containing 200 u M 2,4-D and 0 .2% activated charcoal . 
3. Modif ied Blake ' s med ium described by Ebert and Taylor (1990) 
conta in ing 200 u M 2,4-D and 0 .25% activated charcoal . 
40 
4. Coconut anther culture medium formulated by Tuyen and Guzman 
(1982) containing 10 uM 2,4-D, 10 um naphthaleneacetic acid 
and 0.25° activated charcoal. 
All the cultures were incubated in dark at 30 1 C. 
RESULTS 
The first sign of callogenesis (indicated by floral bud swelling) was 
observed in explants cultured on medium 72 (a medium developed for callus 
induction in immature embryo explants of coconut) after about 8 weeks of 
culturing. This was followed by the initiation of small, whitish calli from 
floral areas (Fig. 1). The callus tissues continued to grow into larger masses 
(without any subculturing) within 12-14 weeks of culturing (Fig. 2). About 
30% of the cultured explants produced embryogenic calli (Fig. 3) on the 
above medium. 
In modified Eeuwens Y3 medium, transluscent outgrowths developed 
directly from the floral buds within 6 weeks of culturing. Some of these 
structures developed into shoots upon subculturing into a medium contain­
ing 8 um 6-benzylaminopurine and 10 uM 2,4-D. However, the frequency 
of shoot regeneration was very low. Roots were induced on these shoots 
(Fig. 4) by dipping in 100 uM indoleacetic acid solution for 3 days followed 
by culturing them in an auxin-free medium as described by Fernando and 
Gamage (1995). 
DISCUSSION 
In the present study, emphasis was placed on callogenesis in flower 
meristem explants as it is the first stage in the process of somatic embryo-
genesis. The results indicate that the culture medium developed for 
callogenesis in immature embryo explants of coconut is also suitable for 
callogenesis in floral explants. Work in progress is directed towards the in­
duction of somatic embryogenesis in the calli obtained. 
The direct shoot regeneration observed in modified Eeuwens Y3 
medium is also of importance as it could lead to the development of a regen­
eration protocol devoid of a callus phase. Thus, attempts will be made to 
refine the culture conditions to increase the frequency of direct shoot forma­
tion. 
4 1 
Fig. I ; Callus initiation on floral explants. (x 3) 
-ig. 2 ; Nodular, embryogcnic callus, (x 3) 
A C K N O W L E D G E M E N T S 
W e are mos t grateful to Mr. E. S. Shantha for his assistance in histo­
logical work. We also gidtefully acknowledge tne assis tance ot Mr. Pemsir i 
Si lva and Mr. H.P. Asoka Kumara the photographers . Thanks are also due to 
the staff of Tissue Culture Division, Coconut Research Institute for their 
ass is tance in performing this investigation. 
References 
Eber t , A . and Taylor, H.F. (1990) . Assessment o f the changes of 2 ,4-
dichlorophenoxyacet ic acid concentrat ions in plant t issue culture media in 
the presence of activated charcoal . Plant Cell Tissue and Organ cul ture 20 : 
165-172. 
Fe rnando , S.C. and Gamage , C.K. (1995) . Clonal propagat ion of coconut : 
Improved cul ture condit ions for rhyzogenesis . C O C O S 10: 20-25 . 
Hornung , H . (1995) . Initiation of cal logenesis in coconut pa lm (Cocos 
nuciferaL.). In Lethal Yellowing: Research and Practical Aspects. 203 -215 . 
(Eds . C. Oropeza et. a l . ) . K luwer Academic Publishers . T h e Nether lands . 
Karunara tne , S. and Per iyapperuma, K. (1989) . Culture o f immature em­
bryos of coconut (Cocos nucifera L.) callus proliferation and somatic e m -
bryogenes is . Plant Sci. 62: 247-253 . 
Karunara tne , S. , Gamage , C. and Kovoor , A., (1991) . Leaf maturity, a 
crit ical factor in embryogenes is . J. Plant Physiol . 139: 2 7 - 3 1 . 
Ri l lo , E.P. (1989) . A nondestruct ive technique for collecting immature c o 
conut inflorescence for tissue culture. Phil. J. Coconut Studies 14(2): 16-17. 
Thanh-Tuen, T.N. and D e Guzman, E.V. (1983) . Format ion o f pol len e m ­
bryos in cultured anthers of coconut (Cocos nucifera L . ) . Plant Science 
Let ters 29 : 81-88 . 
' Verdeil , J . L . , Huet , C . ; G&sdemange , F. and Buffard-Morel, J. (1994) . Plant 
r egenera t ion from cul tured immature inf lorescences of coconu t (Cocos 
nucifera L . ) : Evidence for somatic embryogenesis . Plant Cell Repor ts 13: 
2 1 8 - 2 2 1 . 
4 3 


Callus induction and direct shoot formation in in vitro cultured immature inflorescence tissues of coconut

Fernando, L.C.P.

Chandrasiri, K.A.S.

COCOS (1997), 1 2 , 7 9 - 8 1 
Printed in Sri Lanka. 
Research Note 
MORE EVIDENCE ON THE ATTRACTION OF MALES TO 
THE FEMALE SEX PHERMQNE OF Opisina 
arenosetta-yrvSkex 
L.C.R Fernando and K . A . S . Chandrasirl 
Coconut Research Institute, Lunuwila, Sri Lanka 
Coconu t caterpillar, {Opisina arenosella) is a ser ious pest caus ing 
up to about 8 0 % yield loss in coconut in Sri Lanka (Perera, 1987). S ince , it's 
first appearance in Batt icaloa district (Eastern province), a round the turn of 
the century, has now spread to Western, Southern, North-Western and Cen­
tral provinces . A n average of 250-500 ha of coconut are be ing annually in­
fested whi le half of that extent is subjected to treatment wi th insecticides. 
T h e pr imary reason for outbreaks is cl imatic condit ions. T h e low m i n i m u m 
temperatures that prevail dur ing the October to February period is de t r imen­
tal to both the pest and it's natural enemies , particularly parasi toids. At the 
end of the adverse period, the pest increases rapidly whi le the parasi toids fail 
to d o so for another 3-4 months . This time lag causes the pest outbreak and 
at these pest levels, parasitoid numbers are insufficient to exert control. There­
fore, if parasi toids could be augmented at the'initial s tages of an infestation 
there are high chances of prevent ing onset of outbreaks. To augment labora­
tory-bred parasi toids it is essential to predict when and where early infesta­
t ions occur s ince, the pattern and distribution of the infestations vary consid­
erably each year. 
T h e p resence of a female sex p h e r o m o n e in coconu t caterpil lar , 
Opisina arenosella (Lepidoptera : Oecophoridae) has been revealed from 
studies in India (Murthy et al., 1995) and in Sri Lanka (Mumford et al., 1986). 
Al though, s o m e evidence was present in the prel iminary s tudies carried out 
in Sri Lanka , the results were not conclusive s ince, there was no significant 
difference in the n u m b e r of male moths caught in virgin female-baited traps 
and unbai ted traps. However , baited traps caught more, males than females. 
Therefore , further studies were undertaken to ascertain the attraction of vir­
gin females of Opisina arenosella to conspecific males . Here w e present our 
invest igat ions. 
79 
A 
ThalawOa Kottantivu 
•Baited 
•Unbalted 
•Baited 
•Unbailed 
Ja-ela ThalawOa Kottantivu 
8 0 
T h e exper iment was carried out in three estates in Ja-ela, Thalawi la 
and Kottant ivu infested by coconut caterpillar dur ing the per iod N o v e m b e r 
to December , 1996. O n e to two day old virgin females were individually 
confined in net cages of I t d iameter and 41 tall. Each cage was fixed be tween 
two square (8! x 81) thick plast ic sheets held 41 apart . Inner surfaces of the 
sheets were applied wi th insect g lue to trap the moths attracted to the virgin 
females. T h e size of the traps in the present exper iment was reduced to one 
fourth of that used in the exper iments of Mumford et al. (1986) to min imize 
accidental ca tches . The traps (Isandwich trapsl) were p laced horizontal ly in 
the canopy of the infested trees for two consecut ive nights . Each of 10 bai ted 
and unbai ted traps were set at each location. T h e trap catches of males a n d 
females were recorded at the end of the two days . 
T h e number of male moths caught in baited traps was significantly 
h igher (P<0.001) than in unbai ted traps (Fig. I A ) : T h e n u m b e r of female 
moths caught in both trap types was nearly equal ,with the except ion in t raps 
at Kot tant ivu indicating these were accidental catches ( j i g . I B ) . Hence7the 
results conclusively revealed the attractiveness of virgin females to conspe -
cific ma les of Opisina arenosella clearing the doubts of the earl ier exper i ­
men t s . 
Synthet ic analogues of sex pheromones have been used to forecast 
and mon i to r pes t popula t ions . Similar ly the synthet ic sex p h e r o m o n e o f 
Opisina arenosella would he lp to forecast t ime and locat ion of coconu t ca t ­
erpi l lar pes t infestatipns in t ime sufficient enough to e m p l o y parasi toids and 
thereby prevent development o f outbreaks! T h e componen t s of the phe ro ­
m o n e has been identified by Hal l (1986, unpublished report ) . Therefore fur­
ther s tudies are necessary to identify the natural b lend of the phe romone and 
its effectiveness in the field condit ions. 
REFERENCES 
Mumford , J. D. , Hal l , D . R., Perera, P. A . C. R. and Kanagara tnam, P. (1986J 
Annua l report of the Crop Protection Division, Coconu t Research Insti 
tute of Sri Lanka . 
Murthy , K.S . , Gour , T.B., Reddy, D.D.R., Babu, T.R. and Zaheruddcen , S .M. 
(1995). P h e r o m o n e bai ts for coconut b lack beaded caterpillar, Opisina 
arenosella walker. Insect Envi ronment . 1:3-4. 
Perera, P. A . C. R. (1987). Sudies on Opisina arenosella Walker and it 's natu 
ral enemies in Sri Lanka . Ph D thesis. Universi ty of London . 
81 


More evidence on the attraction of males to the female sex phermone of Opisina arenosella walker

Fernando, S.C.

Tissue culture and gene transformation studies of elite rice breeding lines

Vertebrate pests of coconut in Sri Lanka

National Science Foundation of Sri Lanka

Not a member yet