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Date palm cultivar specific susceptibility to grater date moth infestation.

Introduction

Date palm (Phoenix dactylifera L) is a tree of value and a major food crop of the Arabian Peninsula. The conventional propagation of the date palm is sexually by seeds and vegetatively by offshoots. Since the species is genetically heterogeneous, offshoot propagation was used for many generations to maintain the clonal genetic integrity of the selected cultivars. On the other hand, offshoot propagation is slow, expensive and prone to transmit insects and diseases. Tissue culture micropropagation technology was developed for 30 date palm cultivars and successfully implemented in Kuwait to produce several thousands of young and uniform plants that were planted in orchards for production of dates (Sudhersan et al., 1993a, b; Sudhersan and Aboel-Nil, 2004). An date palm orchard having 5 plants each from 12 different date palm cultivars derived from tissue culture was established during the year 2000 at the main KISR campus, Kuwait for the field evaluation.

Field observations indicated the true-to-type nature of the plants in terms of growth morphology and fruiting (Sudhersan and Aboel-Nil, 2004). However, certain growth abnormalities or physiological disorders such as crown bending, dwarfing and terminal shoot bud death were also observed in few tissue culture derived date palms at the stage of flowering. Laboratory studies indicated that the main cause for these physiological disorders was due to the infestation of the greater date moth Arenepsis sabella followed with fungal infection on the wounds made by the insect larvae (Sudhersan and Al-Shayji, 2007).

During our field evaluation of the tissue culture derived date palms in the first date palm orchard, the above mentioned physiological disorders were noticed only in certain date palm cultivars particularly Sultana and Suckary. Therefore, an experiment was conducted using 12 palms each from 20 different date palm cultivars planted in an orchard during 2004 to study and reconfirm the cultivar based susceptibility to greater date moth larval infestation. The details of the experimental study and the results are presented herein.

Materials and Methods

The experimental date palm orchard developed in 2004 inside the Kuwait Institute for Scientific Research (KISR) campus at Suwaikh containing 12 plants each from 20 different date palm cultivars produced by tissue culture method was used for the study. a total of 240 date palm plantlets of 20 different cultivars were planted in 20 rows by giving 4 m distance between the plants and rows. The palms were maintained uniformly by giving water and nutrients regularly. The orchard was not sprayed with any kind of insecticides or fungicides. All the palms were carefully observed once in a week for any symptoms for diseases or physiological disorders. All observations were recorded.

Infected palms were dissected out to find out the cause for the disorder. All the malformations on the leaves, inflorescence and stem tissue were photographed and recorded. The insect larvae collected from the infected tree were reared in the laboratory for the insect identification.

The affected palms and the palms showing the symptoms of infestation were first treated with Malathion (2 ml/l water) followed by 1 % Benlate solution. Prior to the treatment with insecticide and fungicide, the infected fronds, basal leaf spines and older leaves were removed in order to make it easy to treat the palms. Treated palms were carefully maintained until the complete recovery from the disorder.

Results:

All the tissue culture derived palms planted in the experimental orchard were survived and the plant growth was uniform. During the first 2 years, no dwarfing symptoms were noticed in any of the palms. At the 3 year onwards few trees started producing malformed fronds followed by little leaves. Some of the infected palms showed crown bending and few palms produced little leaves and finally stunted in to a dwarf palm (Fig. 1). Such dwarf palms died after a few months if not treated. The infected palms showed symptoms: front malformation, scratches and furrows on the leaf rachis, absence of leaflets, little leaves, 'v' cut on leaf base, rachis, flower stalks and spathe, leaf drying, leaf whitening, inflorescence without flowers, inflorescence drying, fruit bunch braking, crown bending and dwarfing followed by the death of terminal bud. This physiological disorders were occurred only in two cultivars: Succari and Sultana among the 20 cultivars in the experimental orchard. The percentage of infestation was 58 % in Succari and 67 % in Sultana (Table 1). The insect larval frass was noticed in all the palms during March-April and October-November but, no dwarfing and crown bending occurred in other palms except Succari and Sultana. Dissected out infected palms showed the wounds caused by the larva of the insect moth (Fig.2). Infected palms were completely recovered after treating the palms with insecticide and fungicide solutions at the right time. The palms subjected to this insect larval attack, after treatment, produced axillary shoots which developed into normal palms. The insect larvae was identified and reconfirmed as Arenepsis sabella (Figs.2-4) through laboratory experiments.

Discussion:

The present study reconfirmed that the crown bending and dwarfing in tissue culture derived date palms were caused by the greater date moth Arenepsis sabella. The primary symptoms for this insect larval infestation on date palms are: presence of the insect larval frass (fecal excrement) on the young fronds, frond malformation, whitening of young leaves, "V" cut on leaf rachis, inflorescence axis and spathe, scratches, furrows and holes on the young fronds, and slight bend on the crown. All these symptoms were noticed in many palms belong to different date palm cultivars both originated by tissue culture, offshoot and seedling methods during the month of March to May and September to November. However, all the palms with these symptoms did not show complete palm mortality because the larvae eat the tender leaf tissue or inflorescence, and metamorphosed in to an adult moth within a short period. If the tissue is more palatable to this insect larvae then the larvae eat more tissue, enter inside the shoot tip and eat the meristematic tissue. When a portion of the meristematic tissue is damaged, then the palm showed crown bending and when the entire shoot meristem is damaged, the shoot growth was arrested and the tree became dwarf. The complete death of the tree occurred when the wound caused by the larvae infected by the fungus. In our study, the severe infestation of this larvae leading to crown bending and dwarfing followed by the death of terminal bud occurred only in the cultivars Succary and Sultana. Even though 240 palm trees belonging to 20 different cultivars available in the orchard, the larvae infected severely only the cultivars Succari and Sultana which clearly confirmed that these two cultivars are more susceptible to the greater date moth.

Tree crown bending and dwarfism observed in tissue cultured date palms were reported as offtypes originated by tissue culture. Sudhersan and Al-Shayji (2005) reported that these offtypes noticed in tissue culture derived date palms are physiological disorders common to all types (tissue culture derived, offshoot derived and seedling derived) of date palms and this disorders were caused by the larvae of the greater date moth Arenepsis sabella Hamps. (Sudhersan and Al-Shayji, 2005). Many insects attack the floral and vegetative parts of the date palm trees (AbuThuraya and Al-Buraidi, 1989; Hammad et al., 1983; Kadous et al., 1983). However, the larvae of the greater date moth particularly caused the frond malformation, "V" cut or cross cut in fronds, inflorescence axis and spathes, crown bending, and dwarfing followed by terminal shoot death in date palms. At the initial stages of infestation with the larvae of greater date moth the young leaves showed malformations in the leaflets and rachis. The crown bending is due to the damage of the meristematic tissue and young fronts at one side of the growing point. The new leaf production and growth of the fronds on the other parts make the entire tree crown bends towards the point of insect or fungal attack. If the initial infestation was at the base of a leaf, larvae feed on the leaf tissue disrupting the vascular flow causing death of the entire leaf. Few months after insect infestation, fungal infection through wounds followed and extended into the terminal meristem. Axillary shoots that developed from buds at the axils of unaffected leaves develop into normal offshoots. On the other hand, if the insect infestation was not treated, offshoots may also get infested and show the symptom of frond malformation. Palms that show any sign of leaf malformation or death of a single leaf or presence of the frass of the insect on the leaves should be treated for insect infestation by spraying the entire tree with a systemic insecticide.

Crosscut or 'V'-cuts of fruit stalks and fronds reported from the United States, Pakistan and a few Middle East countries (Djerbi, 1980). According to the previous reports, crosscuts, are clean breaks in the tissue of the fruit stalk bases and on fronds resulted from an anatomical defect causing mechanical breaks during elongation. According to J. B. Carpenter (Carpenter, 1975) Sayer and Khadrawy varieties are especially susceptible to this disorder and are no longer propagated in some countries. Recent studies carried out at KISR indicated that this crosscut is caused by the greater date palm moth Arenipses sabella infection and it is noticed not only in selected cultivars but in many date palm cultivars in Kuwait.

Barhee disorder is characterized by an unusual bending of the crown of Barhee variety. It was reported in California (Darley et al., 1960), Iraq (Husssain, 1974) and Israel (Zaid, 1996). Affected palms were found to bend mostly to the south and sometimes to the southwest. Djerbi (1983) observed this disorder in cultivars Jahla and Aguellid. The reason for this disorder is reported to be unknown and can be corrected within two years. Recent study carried out at KISR indicated that this crown bending is common in date palms (not limited to a particular variety) and it is caused by unbalanced bunches of fruits or insect attack at one side of the shoot bud (Sudhersan and Yousif Al-Shayji, 2006).

Bending head, called "Le Coeur qui penche" in French, is reported as a minor disease observed in Algeria, Egypt, Mauritania and Tunisia (Munier, 1955). The central cluster of fronds takes the form of an erect fascicle with a bent tip. The trunk bends and may even break. Our study indicated that this problem is due to the infestation by the moth Arenipses sabella at one side of the growing meristematic area. Previous reports indicated that Thielaviopsis paradoxa and Botryodiplodia theobromae Pat. are fungi commonly isolated from declining palms (Brun and Laville, 1965). These fungi may be a secondary infection through the wound caused by the insect larvae. Efficient maintenance and appropriate sanitation of the date plantation is the first control measure. Diseased parts of infested palms are to be collected and burnt in order to limit the spread of the disease.

Most of these physiological disorders in date palms were reported already as diseases of unknown origin in date palms. Recent observations by the author indicates that the real cause for the date palm disorders such as frond malformation, 'v' cut, crown bending, death of terminal bud and little leaf syndrome are caused by insect larvae of the date moth Arenipses sabella and followed by the secondary infection of fungi through the wound caused by the larvae.

Conclusion:

Many physiological disorders were reported as unknown diseases in date palms. The present study confirmed that these reported unknown diseases of date palm such as crown bending, 'V' cut, dwarfing etc are physiological disorders caused by insect larval attack followed by fungal infection. The insect was identified as Arenipses sabella Hamps (grater date moth). Generally, the symptoms of these physiological disorders were observed in many unknown date palm cultivars. However, the present study confirmed that certain date palm cultivars are highly susceptible to the grater date moth. Among the 20 known date palm cultivars studied, only Suckary and Sultana are affected by this insect larvae. The palms affected by these physiological disorders could be returned to the normal condition through insect or pathogen control at the proper time. Since the date palm cultivars Succari and Sultana are more susceptible to this insect, it is very important that these two date palm cultivars need special care on good control over insect pests and pathogens at early stages of growth and establishment. As a control measure for this moth, chemical control is inevitable solution until finding out an alternative environmentally friendly method for the control of this date palm moth Arenipses sabella.

Acknowledgement

The encouragement and support by the KISR management to carry out the research activity is hereby acknowledged.

References

Al-Shayji, Y and C. Sudhersan, 2008. Pseudo dwarf disorder in tissue cultured date palms. AEJSR 3(2): 128131.

Abu Thuraya, N.H. and F.H. Al-Buraidi, 1989. List of date palm pests andtheir economic importance in Saudi

Arabia. Proceedings of the Second Symposium on the Date Palm. Al-Hassa, Saudi Arabia. Mars Publishing House, Riyadh, Saudi Arabia, pp: 345-357.

Carpenter, J.B., 1975. Notes on the Arab culture in the Arab Republic of Egypt and the People's Republic of Yemen. Date Grower's Inst. Report., 52: 18-24.

Darley, E.F., R.W. Nixon and D. Wilbur, 1960. An unusual disorder of barhee date palms. Ann. Date Grower's Inst. 37: 10-12.

Djerby, M., 1980. Report on duty travel to Tunis, Baghdad and Pakistan. FAO Regional Project for Palm and Dates Research Center in the Near East and North Africa, Baghdad, Iraq. pp: 10.

Djerby, M., 1983. Diseases of the Date Palm. FAO Regional project for Palms and Date Research Center in the Near East and North Africa, Baghdad, Iraq. pp: 106.

Hamad, S. M., A.A. Kadous and M.M. Ramadan, 1983. Predators and parasites of date palm insects in Al-Hassa and Al-Qatif regions, Saudi Arabia. Proceedings of the First Symposium on the Date Palm. King Faisal University, Al-Hassa, Saudi Arabia, pp: 322-341.

Kadous, A.A., S.M. Hamad and M.M. Ramadan, 1983. Assessment of damage inflicted upon date palms by Pseudophilus testaceus and Oryctes elegans in Al-Hassa oasis. Proceedings of the First Symposium on the Date Palm. King Faisal University, Al-Hassa, Saudi Arabia, pp: 352-361.

Stickney, F.A., D.A. Barnes and P. Simmons, 1950. Date palm insects in the United States. USDA, Washington DC, pp: 846.

Sudhersan, C., M.M. AboEl-Nil and A. Al-Baiz, 1993a. Occurrence of direct somatic embryogenesis on the sword leaf of in vitro plantlets of Phoenix dactylifera L, cultivar Barhee. Current Science, 65: 887-888.

Sudhersan, C., M.M. AboEl-Nil and A. Al-Baiz, 1993b. Direct somatic embryogenesis and plantlet formation from the leaf explants of Phoenix dactylifera L. cultivar Barhi. J. Swamy Bot. Cl. 10: 37-43.

Sudhersan, C., and M. AboEl-Nil. 2004. Axillary shoot production in micropropagated date palm. Current Science, 86: 771-773.

Sudhersan, C. and Y. Al-Shayji, 2007. A study on physiological disorders of tissue cultured date palms in Kuwait. Technical Report, KISR No. 8800, KISR, Kuwait.

Biotechnology Program, Environment and Life Science Centre Kuwait Institute for Scientific Research, P.O.Box 24885, Safat 13109, Kuwait

C. Sudhersan: Date Palm Cultivar Specific Susceptibility To Grater Date Moth Infestation

Corresponding Author: C. Sudhersan, Biotechnology Program, Environment and Life Science Centre Kuwait Institute for Scientific Research,

P.O. Box 24885, Safat 13109, Kuwait; E-mail: schellan@kisr.edu.kw

Table 1: Date palm cultivar susceptibility to Arenepsis sabella

Date Palm Cultivar   Total No.   Total No. of     % of
                     of Palms    Palms Infected   Infection

1. Anbara            12          0                0
2. Ashgar            12          0                0
3. Awaidhi           12          0                0
4. Barhi             12          0                0
5. Fersi             12          0                0
6. Hilali            12          0                0
7. Jouzi             12          0                0
8. Khlas             12          0                0
9. Khasab            12          0                0
10. Kyarah           12          0                0
11. Lolwi            12          0                0
12. Majdhool         12          0                0
13. Makdoomy         12          0                0
14. Qantat           12          0                0
15. Sagar            12          0                0
16. Shishi           12          0                0
17. Succari          12          7                58
18. Sultana          12          6                50
19. Siwi             12          0                0
20. Seik Ali         12          0
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Article Details
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Title Annotation:Original Article
Author:Sudhersan, C.
Publication:American-Eurasian Journal of Sustainable Agriculture
Article Type:Report
Geographic Code:7KUWA
Date:Jan 1, 2013
Words:2666
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