corm rot of giant swamp taro ( cyrtosperma merkusii ... · corm rot of giant swamp taro (...
TRANSCRIPT
Nematology 2005 Vol 7(4) 631-636
Corm rot of giant swamp taro (Cyrtosperma merkusii) caused bythe burrowing nematode Radopholus similis (Nematoda
Pratylenchidae) in the Pacific
Vazhaveli K MURUKESAN 1 Esther VAN DEN BERG 2 Laurens R TIEDT 3Puthiyaparambil C JOSEKUTTY 4 and Dirk DE WAELE 5lowast
1 College of Micronesia Yap State Campus PO Box 1226 Colonia YAP FM 96943 Federated States of Micronesia2 National Collection of Nematodes Biosystematics Division Plant Protection Research Institute Private Bag X134
Queenswood 0121 South Africa3 Laboratory for Electron Microscopy North West University Potchefstroom Campus Potchefstroom 2520 South Africa
4 Cellular and Molecular Biology Laboratory School of Biological Sciences University of CanterburyPrivate Bag 4800 Christchurch New Zealand
5 Laboratory of Tropical Crop Improvement Catholic University Leuven (KULeuven)Kasteelpark Arenberg 13 3001 Leuven Belgium
Received 28 February 2005 revised 5 July 2005Accepted for publication 6 July 2005
Summary ndash The association between the burrowing nematode Radopholus similis and giant swamp taro is studied in detail for thefirst time in corms collected from swampy taro patches in Yap one of the states of the Federated States of Micronesia The R similispopulation from Yap displays similar variation in morphometrics and morphology as reported in the literature The rot caused by thenematodes is wet with a loose mass of brown dead tissues and a deep brown necrotic centre housing nematodes inside Usually theinfected tissues spread a disgusting odour typical of this disease The dead tissues progress into shallow to deep cavities that advancetowards the edible central portion of the corm giving a perforated appearance on the outside of the otherwise smooth corm Thedisease becomes more severe as the age of the plant increases Nematode-infected plants seldom show any above-ground symptomsThe market quality of the corm is greatly reduced by the nematode damage The widespread occurrence of the disease and the typeof damage R similis causes to the corms pose a serious threat to giant swamp taro production food security and the continuation oftraditional customs on those islands where R similis occurs
Keywords ndash Federated States of Micronesia plant-parasitic nematode symptomatology Yap
Giant swamp taro Cyrtosperma merkusii (Hassk)Schott is an important crop on many Pacific islands whereit is grown in flooded swamp land for its large ediblecorms It is an important source of starch is rich in naturalfibres and carbohydrates and is low in fat In Yap oneof the states of the Federated States of Micronesia anadult consumes about 800 g fresh weight of corm daily(Nakano 1999) Some of the yellow cultivars are reportedto be high in carotenoids making them an ideal localresource to fight vitamin A deficiency among the peopleof the Pacific islands (Englberger et al 2003) The cropis not seasonal and withstands strong winds the cormhaving the potential to remain in the ground for 10 years
lowast Corresponding author e-mail DirkDeWaelebiwkuleuvenbe
or more and thereby provide food security Moreovergiant swamp taro also plays a significant role in thetraditional life of the islanders especially in Yap wherefor many centuries it has been considered a cultivatedplant of status and where a healthy corm has a significantvalue in funerals and traditional ceremonies Corms fromplants 10 or more years old are among the most highlyprized gifts that a person can give to chiefs during thesefunerals and ceremonies Also a number of strong taboosand restrictions surround the cultivation of giant swamptaro and its preparation for food
In 1987 a corm rot of Cyrtosperma caused by Radopho-lus similis (Cobb 1893) Thorne 1949 was reported from
copy Koninklijke Brill NV Leiden 2005 631Also available online - wwwbrillnl
VK Murukesan et al
the Pacific islands of Yap Palau and Guam (Jackson1987) Infected corms had small shallow holes as if theyhad been bored by insects the holes being 05-2 cm indiam and 1-2 cm deep Beneath this tissue was a brownrot mostly superficial but occasionally extending as nar-row channels deep into the centre of the corm Becauseof the rot a considerable amount of decayed tissue hadto be pared away before corms became fit for humanconsumption Infected plants showed little above-groundsymptoms Large numbers of R similis were found in thecorms but relatively few in the roots (Jackson 1987)As R similis had not previously been reported from Cyr-tosperma and an anaerobic flooded swamp was thoughtan unlikely habitat for this nematode species specimenswere sent to the Institute of Parasitology in St AlbansEngland where the identification was confirmed by tax-onomists Grandison (1990) reported that in Yap andPalau the incidence of corm rot of giant swamp tarocaused by R similis was at least 80 and that there wereindications that the disease had become more important inrecent years In a recent study in Yap (Onjo et al 2001)the validity of R similis being the causal agent of drycorm rot of giant swamp taro was questioned as the au-thors failed to extract R similis from diseased corms Asno detailed study of this interesting and important plant-nematode interaction had ever been made samples wereonce again collected in Yap for further study
In the present study the identity and the role of Rsimilis in corm rot of giant swamp taro is confirmedInformation is given on the morphology of R similisisolated from Cyrtosperma and the symptoms caused bythis nematode species documented Implications for thepractical management of R similis on giant swamp taroare discussed
Materials and methods
Infected corms were collected from a knee-deep swam-py taro patch at Gagil Municipality Yap and brought tothe laboratory in an ice chest Main and feeder roots werecut off and the corms gently washed to remove the mudand soil particles Small pieces of infected corms togetherwith encircling healthy portions were wrapped in tissuepaper and sent to the Plant Protection Research Institutein Pretoria South Africa for isolation of the nematodesand identification
For mounting the nematodes were transferred to for-malin-propionic acid-glycerin (FPG) and mounted in an-hydrous glycerin (Netscher amp Seinhorst 1969 Hooper amp
Evans 1993) For scanning electron microscopy speci-mens were killed and fixed in TAF after which they weredehydrated in increasing concentrations of amyl acetatein pure alcohol and finally in pure amyl acetate Follow-ing conventional critical point drying and goldpalladiumcoating (15 nm) specimens were viewed with a PhilipsXL30 DX41 stereoscan microscope at 10Kv For in situstudies corm tissue was placed in a concentration of 30acetone overnight and then for 30 min each in concentra-tions of 75 95 and then left in 100 acetone Thecorm tissue was then critical point dried and coated andviewed as described above for the nematode specimens
Results and discussion
MEASUREMENTS
See Table 1 for morphometrics of female and malenematodes
MORPHOLOGICAL OBSERVATIONS
The R similis specimens from Yap compare very wellwith various descriptions of this species (Koshy et al1991 Ryss amp Wouts 1997 Valette et al 1998 Elbadriet al 1999a b) (Fig 1) These authors made detailedstudies of the morphology and morphometrics of Rsimilis populations from many different countries and hostplants They found a substantial variation in all cuticularand morphometrical characters of both females and malesThe population from Yap displays similar variation asrecorded by these authors
DISEASE SYMPTOMS
The nematode-infected plants seldom show any above-ground symptoms Giant swamp taro is a perennial cropand the disease becomes more severe as the age of theplant increases The disease has in the past been namedlsquodry corm rotrsquo to distinguish it from soft rots caused bybacteria and fungi and in analogy with dry rots caused byRadopholus and Pratylenchus spp in other root and tubercrops such as yam Our observations however show thatthe infected necrotic tissues are not dry as the originalname of the disease suggests On the corms from Yapexamined in the present study the rot is wet with a loosemass of brown dead tissues and a deep brown necroticcentre housing nematodes inside (Fig 2A B) Usuallythe infected tissues produce a disgusting odour which isso typical of this disease Corms are ready for harvest
632 Nematology
Corm rot of giant swamp taro
Table 1 Morphometrics of adult Radopholus similis from Yap Island All measurements are in microm and in the form mean plusmn standarddeviation (range)
Female Male
n 23 11L 604 plusmn 54 (503-726) 586 plusmn 542 (454-646)a 26 plusmn 34 (21-311) 328 plusmn 46 (235-40)b 74 plusmn 07 (59-88) 73 plusmn 07 (61-84)b1 45 plusmn 03 (38-5) 54 plusmn 03 (49-59)c 87 plusmn 07 (78-108) 8 plusmn 06 (65-84)c1 41 plusmn 04 (34-46) 52 plusmn 02 (49-57)o 201 plusmn 36 (13-267) ndashV 57 plusmn 16 (53-595) ndashDGO 3 plusmn 05 (2-4) ndashOV1 23 plusmn 51 (19-43) ndashOV2 21 plusmn 29 (17-29) ndashStylet length 165 plusmn 05 (15-17) ndashMetenchium length 8 plusmn 04 (8-85) ndashTelenchium length 85 plusmn 05 (8-9) ndashStylet knob height 2 plusmn 03 (15-25) ndashStylet knob width 35 plusmn 03 (3-45) ndashMedian bulb length 125 plusmn 11 (11-14) 11 plusmn 14 (8-13)Median bulb diam 95 plusmn 11 (8-125) 5 plusmn 05 (45-6)Lip region diam 95 plusmn 06 (8-10) 75 plusmn 06 (65-9)Lip region height 35 plusmn 04 (25-4) 55 plusmn 04 (5-6)Pharynx length 135 plusmn 88 (119-156) 1095 plusmn 116 (94-1285)Pharynx gland length 53 plusmn 9 (37-66) 305 plusmn 83 (165-42)Excretory pore from anterior end 875 plusmn 65 (69-99) 92 plusmn 84 (80-120)Diam at midbody 235 plusmn 49 (16-33) 18 plusmn 2 (155-205)Diam at excretory pore 21 plusmn 22 (175-26) 16 plusmn 06 (55-17)Diam at anus 165 plusmn 22 (13-22) 14 plusmn 03 (135-15)Diam at start of hyaline part 6 plusmn 05 (5-75) 5 plusmn 08 (45-65)Annulus width 15 plusmn 02 (1-2) 13 plusmn 02 (1-15)Lateral field width 65 plusmn 1 (55-9) 5 plusmn 07 (4-6)Tail length 68 plusmn 6 (53-77) 73 plusmn 3 (695-79)Number of tail annuli 52 plusmn 45 (44-60) ndashh 10 plusmn 18 (7-14) 9 plusmn 17 (65-115)Spiculum length ndash 215 plusmn 09 (20-23)Gubernaculum length ndash 11 plusmn 04 (10-12)
from 3 years after planting thus giving ample time forthe nematodes to become established in large populationdensities inside the corms The end result of nematodeinfection is the formation of shallow to deep cavitiesof dead tissues that advance towards the edible centralportion of the corm (Fig 2C) Infection is visible on theexternal surface of the corm as a perforated appearance ofthe otherwise smooth corm (Fig 2D) This damage highlyreduces the market quality of the corm
The widespread occurrence of the disease and the typeof damage R similis causes to the corms pose a serious
threat to giant swamp taro production food security andthe continuation of traditional customs on those islandswhere R similis occurs
Up to 50 000 R similis juveniles females and maleswere extracted from 10 g of fresh corm A stereoscanmicroscopy study revealed the high population densitiesof R similis inside the corm tissues Interestingly inaddition to R similis several specimens of a largeunidentified dorylaimid were also observed It is possiblethat this nematode species is a predator feeding on thenumerous juvenile and adult R similis The occurrence
Vol 7(4) 2005 633
VK Murukesan et al
Fig 1 Radopholus similis A Anterior part of female body B Anterior part of male body C Female vulval area with twospermathecae of equal size D Male tail E Female tail F-H Tail tip variations in female I Male lateral field at midbody J-LTail tip variations in male M Female lateral field at midbody (Scale bar A-M = 20 microm)
of concentrations of R similis eggs indicates that thisnematode species can reproduce inside the corm and maysuggest that R similis spends its entire life cycle insidethe giant swamp taro plant tissue thereby avoiding theanaerobic conditions of the flooded swamp AlthoughR similis has a been reported from many islands inthe Pacific and from many host plants including taro(Colocasia esculenta (L) Schott) and yam (Dioscoreaspp ie see Bridge 1988) the occurrence of thisnematode species in a swamp environment is uncommonand has not been reported previously If our hypothesisthat R similis does not occur in the rhizosphere ofthe plants is correct planting nematode-free cormlets
could prevent the spread of the disease In giant swamptaro new cormlets develop from the outer surface ofthe mother corms as side shoots approximately 1-2years after planting At harvest the cormlets are cut offclose to the point of attachment with the mother cormsCurrently excised cormlets are the only type of plantingmaterial used in Yap Nematode-free cormlets could beproduced via in vitro micropropagation and nematode-infected cormlets could be disinfected via heat treatmentThermotherapy has proven effective in eliminating Rsimilis from infected palms and Anthurium (Tsang et al2003 Arcinas et al 2004)
634 Nematology
Corm rot of giant swamp taro
Fig 2 A 9-year-old infected corm with wet loose mass of brown dead tissue (scale bar = 3 cm) B 2-year-old infected corm cutsuperficial diagonally showing the deep brown necrotic centre (arrow) (scale bar = 1 cm) C 8-year-old infected corm cut in halfshowing cavities of dead tissues that advance towards the edible central portion of the corm (arrows) (scale bar = 2 cm) D Entireinfected corms showing the perforated appearance of the otherwise smooth corm (scale bar = 2 cm)
Acknowledgements
Dr Singeru Singeo Executive Director College ofMicronesia-Land Grant Program and Mrs Kenye Killin
CES Assistant Director College of Micronesia-FSMKosrae Campus are gratefully acknowledged for thefinancial assistance provided from ADAP and USDA-IPM grants respectively Mrs NH Buckley of the PlantProtection Research Institute is thanked for technicalassistance
Vol 7(4) 2005 635
VK Murukesan et al
References
ARCINAS AC SIPES BS HARA AH amp TSANGMMC (2004) Hot water drench treatments for the con-trol of Radopholus similis in Rhapis and fishtail palmsHortScience 39 578-579
BRIDGE J (1988) Plant-parasitic nematode problems in thePacific Islands Journal of Nematology 20 173-183
ELBADRI GAA GERAERT E amp MOENS M (1999a)Morphological differences among Radopholus populations(Nematoda Tylenchida) from banana in Africa Journal ofNematode Morphology and Systematics 2 7-16
ELBADRI GAA GERAERT E amp MOENS M (1999b)Morphological differences among Radopholus similis (Cobb1893) Thorne 1949 populations Russian Journal of Nemato-logy 7 139-153
ENGLBERGER L SCHIERLE J MARKS JC amp FITZGER-ALD MH (2003) Micronesian banana taro and otherfoods newly recognized sources of provitamin A and othercarotenoids Journal of Food Composition and Analysis 163-19
GRANDISON GS (1990) Investigation of a nematode disorderof giant swamp taro (Cyrtosperma chamissonis) Report ona visit to State of Yap (Federated States of Micronesia) andRepublic of Palau 3-8 June 1990 Department of Scientificand Industrial Research Auckland New Zealand 14 pp
HOOPER DJ amp EVANS K (1993) Extraction identificationand control of plant nematodes In Evans K TrudgillDL amp Webster JM (Eds) Plant parasitic nematodes intemperate agriculture Wallingford UK CABI Publishingpp 31-59
JACKSON GVH (1987) Corm rot of Cyrtosperma in GuamReport to Federated States of Micronesia and Palau
KOSHY PK JASY T MATHEW J amp NAMPOOTHIRICK (1991) Morphometric variability in Radopholus similisIndian Journal of Nematology 21 24-38
NAKANO K (1999) The supply of energy-source foodstuffs inthe Yap Islands a preliminary report Kagoshima UniversityResearch Center for the Pacific Islands 13 pp
NETSCHER C amp SEINHORST JW (1969) Propionic acidbetter than acetic acid for killing nematodes Nematologica15 286
ONJO M TAURA S amp SAKAMAKI Y (2001) The presentsituation of agriculture in Yap In Aoyama T (Ed) Progressreport of the 1999 survey of the research project lsquoSocialhomeostasis of small islands in an island-zonersquo KagoshimaUniversity Center for the Pacific Islands Occasional PapersNo 34 pp 91-93
RYSS AY amp WOUTS WM (1997) The genus Radopholus(Nematoda Pratylenchidae) from native vegetation in NewZealand with descriptions of two new species InternationalJournal of Nematology 7 1-17
TSANG MMC HARA AH amp SIPES BS (2003) Hot-water treatments of potted palms to control the burrowingnematode Radopholus similis Crop Protection 22 589-593
VALETTE C MOUNPORT D NICOLE M SARAH J-L ampBAUJARD P (1998) Scanning electron microscope study oftwo African populations of Radopholus similis (NematodaPratylenchidae) and proposal of R citrophilus as a juniorsynonym of R similis Fundamental and Applied Nematology21 139-146
636 Nematology
VK Murukesan et al
the Pacific islands of Yap Palau and Guam (Jackson1987) Infected corms had small shallow holes as if theyhad been bored by insects the holes being 05-2 cm indiam and 1-2 cm deep Beneath this tissue was a brownrot mostly superficial but occasionally extending as nar-row channels deep into the centre of the corm Becauseof the rot a considerable amount of decayed tissue hadto be pared away before corms became fit for humanconsumption Infected plants showed little above-groundsymptoms Large numbers of R similis were found in thecorms but relatively few in the roots (Jackson 1987)As R similis had not previously been reported from Cyr-tosperma and an anaerobic flooded swamp was thoughtan unlikely habitat for this nematode species specimenswere sent to the Institute of Parasitology in St AlbansEngland where the identification was confirmed by tax-onomists Grandison (1990) reported that in Yap andPalau the incidence of corm rot of giant swamp tarocaused by R similis was at least 80 and that there wereindications that the disease had become more important inrecent years In a recent study in Yap (Onjo et al 2001)the validity of R similis being the causal agent of drycorm rot of giant swamp taro was questioned as the au-thors failed to extract R similis from diseased corms Asno detailed study of this interesting and important plant-nematode interaction had ever been made samples wereonce again collected in Yap for further study
In the present study the identity and the role of Rsimilis in corm rot of giant swamp taro is confirmedInformation is given on the morphology of R similisisolated from Cyrtosperma and the symptoms caused bythis nematode species documented Implications for thepractical management of R similis on giant swamp taroare discussed
Materials and methods
Infected corms were collected from a knee-deep swam-py taro patch at Gagil Municipality Yap and brought tothe laboratory in an ice chest Main and feeder roots werecut off and the corms gently washed to remove the mudand soil particles Small pieces of infected corms togetherwith encircling healthy portions were wrapped in tissuepaper and sent to the Plant Protection Research Institutein Pretoria South Africa for isolation of the nematodesand identification
For mounting the nematodes were transferred to for-malin-propionic acid-glycerin (FPG) and mounted in an-hydrous glycerin (Netscher amp Seinhorst 1969 Hooper amp
Evans 1993) For scanning electron microscopy speci-mens were killed and fixed in TAF after which they weredehydrated in increasing concentrations of amyl acetatein pure alcohol and finally in pure amyl acetate Follow-ing conventional critical point drying and goldpalladiumcoating (15 nm) specimens were viewed with a PhilipsXL30 DX41 stereoscan microscope at 10Kv For in situstudies corm tissue was placed in a concentration of 30acetone overnight and then for 30 min each in concentra-tions of 75 95 and then left in 100 acetone Thecorm tissue was then critical point dried and coated andviewed as described above for the nematode specimens
Results and discussion
MEASUREMENTS
See Table 1 for morphometrics of female and malenematodes
MORPHOLOGICAL OBSERVATIONS
The R similis specimens from Yap compare very wellwith various descriptions of this species (Koshy et al1991 Ryss amp Wouts 1997 Valette et al 1998 Elbadriet al 1999a b) (Fig 1) These authors made detailedstudies of the morphology and morphometrics of Rsimilis populations from many different countries and hostplants They found a substantial variation in all cuticularand morphometrical characters of both females and malesThe population from Yap displays similar variation asrecorded by these authors
DISEASE SYMPTOMS
The nematode-infected plants seldom show any above-ground symptoms Giant swamp taro is a perennial cropand the disease becomes more severe as the age of theplant increases The disease has in the past been namedlsquodry corm rotrsquo to distinguish it from soft rots caused bybacteria and fungi and in analogy with dry rots caused byRadopholus and Pratylenchus spp in other root and tubercrops such as yam Our observations however show thatthe infected necrotic tissues are not dry as the originalname of the disease suggests On the corms from Yapexamined in the present study the rot is wet with a loosemass of brown dead tissues and a deep brown necroticcentre housing nematodes inside (Fig 2A B) Usuallythe infected tissues produce a disgusting odour which isso typical of this disease Corms are ready for harvest
632 Nematology
Corm rot of giant swamp taro
Table 1 Morphometrics of adult Radopholus similis from Yap Island All measurements are in microm and in the form mean plusmn standarddeviation (range)
Female Male
n 23 11L 604 plusmn 54 (503-726) 586 plusmn 542 (454-646)a 26 plusmn 34 (21-311) 328 plusmn 46 (235-40)b 74 plusmn 07 (59-88) 73 plusmn 07 (61-84)b1 45 plusmn 03 (38-5) 54 plusmn 03 (49-59)c 87 plusmn 07 (78-108) 8 plusmn 06 (65-84)c1 41 plusmn 04 (34-46) 52 plusmn 02 (49-57)o 201 plusmn 36 (13-267) ndashV 57 plusmn 16 (53-595) ndashDGO 3 plusmn 05 (2-4) ndashOV1 23 plusmn 51 (19-43) ndashOV2 21 plusmn 29 (17-29) ndashStylet length 165 plusmn 05 (15-17) ndashMetenchium length 8 plusmn 04 (8-85) ndashTelenchium length 85 plusmn 05 (8-9) ndashStylet knob height 2 plusmn 03 (15-25) ndashStylet knob width 35 plusmn 03 (3-45) ndashMedian bulb length 125 plusmn 11 (11-14) 11 plusmn 14 (8-13)Median bulb diam 95 plusmn 11 (8-125) 5 plusmn 05 (45-6)Lip region diam 95 plusmn 06 (8-10) 75 plusmn 06 (65-9)Lip region height 35 plusmn 04 (25-4) 55 plusmn 04 (5-6)Pharynx length 135 plusmn 88 (119-156) 1095 plusmn 116 (94-1285)Pharynx gland length 53 plusmn 9 (37-66) 305 plusmn 83 (165-42)Excretory pore from anterior end 875 plusmn 65 (69-99) 92 plusmn 84 (80-120)Diam at midbody 235 plusmn 49 (16-33) 18 plusmn 2 (155-205)Diam at excretory pore 21 plusmn 22 (175-26) 16 plusmn 06 (55-17)Diam at anus 165 plusmn 22 (13-22) 14 plusmn 03 (135-15)Diam at start of hyaline part 6 plusmn 05 (5-75) 5 plusmn 08 (45-65)Annulus width 15 plusmn 02 (1-2) 13 plusmn 02 (1-15)Lateral field width 65 plusmn 1 (55-9) 5 plusmn 07 (4-6)Tail length 68 plusmn 6 (53-77) 73 plusmn 3 (695-79)Number of tail annuli 52 plusmn 45 (44-60) ndashh 10 plusmn 18 (7-14) 9 plusmn 17 (65-115)Spiculum length ndash 215 plusmn 09 (20-23)Gubernaculum length ndash 11 plusmn 04 (10-12)
from 3 years after planting thus giving ample time forthe nematodes to become established in large populationdensities inside the corms The end result of nematodeinfection is the formation of shallow to deep cavitiesof dead tissues that advance towards the edible centralportion of the corm (Fig 2C) Infection is visible on theexternal surface of the corm as a perforated appearance ofthe otherwise smooth corm (Fig 2D) This damage highlyreduces the market quality of the corm
The widespread occurrence of the disease and the typeof damage R similis causes to the corms pose a serious
threat to giant swamp taro production food security andthe continuation of traditional customs on those islandswhere R similis occurs
Up to 50 000 R similis juveniles females and maleswere extracted from 10 g of fresh corm A stereoscanmicroscopy study revealed the high population densitiesof R similis inside the corm tissues Interestingly inaddition to R similis several specimens of a largeunidentified dorylaimid were also observed It is possiblethat this nematode species is a predator feeding on thenumerous juvenile and adult R similis The occurrence
Vol 7(4) 2005 633
VK Murukesan et al
Fig 1 Radopholus similis A Anterior part of female body B Anterior part of male body C Female vulval area with twospermathecae of equal size D Male tail E Female tail F-H Tail tip variations in female I Male lateral field at midbody J-LTail tip variations in male M Female lateral field at midbody (Scale bar A-M = 20 microm)
of concentrations of R similis eggs indicates that thisnematode species can reproduce inside the corm and maysuggest that R similis spends its entire life cycle insidethe giant swamp taro plant tissue thereby avoiding theanaerobic conditions of the flooded swamp AlthoughR similis has a been reported from many islands inthe Pacific and from many host plants including taro(Colocasia esculenta (L) Schott) and yam (Dioscoreaspp ie see Bridge 1988) the occurrence of thisnematode species in a swamp environment is uncommonand has not been reported previously If our hypothesisthat R similis does not occur in the rhizosphere ofthe plants is correct planting nematode-free cormlets
could prevent the spread of the disease In giant swamptaro new cormlets develop from the outer surface ofthe mother corms as side shoots approximately 1-2years after planting At harvest the cormlets are cut offclose to the point of attachment with the mother cormsCurrently excised cormlets are the only type of plantingmaterial used in Yap Nematode-free cormlets could beproduced via in vitro micropropagation and nematode-infected cormlets could be disinfected via heat treatmentThermotherapy has proven effective in eliminating Rsimilis from infected palms and Anthurium (Tsang et al2003 Arcinas et al 2004)
634 Nematology
Corm rot of giant swamp taro
Fig 2 A 9-year-old infected corm with wet loose mass of brown dead tissue (scale bar = 3 cm) B 2-year-old infected corm cutsuperficial diagonally showing the deep brown necrotic centre (arrow) (scale bar = 1 cm) C 8-year-old infected corm cut in halfshowing cavities of dead tissues that advance towards the edible central portion of the corm (arrows) (scale bar = 2 cm) D Entireinfected corms showing the perforated appearance of the otherwise smooth corm (scale bar = 2 cm)
Acknowledgements
Dr Singeru Singeo Executive Director College ofMicronesia-Land Grant Program and Mrs Kenye Killin
CES Assistant Director College of Micronesia-FSMKosrae Campus are gratefully acknowledged for thefinancial assistance provided from ADAP and USDA-IPM grants respectively Mrs NH Buckley of the PlantProtection Research Institute is thanked for technicalassistance
Vol 7(4) 2005 635
VK Murukesan et al
References
ARCINAS AC SIPES BS HARA AH amp TSANGMMC (2004) Hot water drench treatments for the con-trol of Radopholus similis in Rhapis and fishtail palmsHortScience 39 578-579
BRIDGE J (1988) Plant-parasitic nematode problems in thePacific Islands Journal of Nematology 20 173-183
ELBADRI GAA GERAERT E amp MOENS M (1999a)Morphological differences among Radopholus populations(Nematoda Tylenchida) from banana in Africa Journal ofNematode Morphology and Systematics 2 7-16
ELBADRI GAA GERAERT E amp MOENS M (1999b)Morphological differences among Radopholus similis (Cobb1893) Thorne 1949 populations Russian Journal of Nemato-logy 7 139-153
ENGLBERGER L SCHIERLE J MARKS JC amp FITZGER-ALD MH (2003) Micronesian banana taro and otherfoods newly recognized sources of provitamin A and othercarotenoids Journal of Food Composition and Analysis 163-19
GRANDISON GS (1990) Investigation of a nematode disorderof giant swamp taro (Cyrtosperma chamissonis) Report ona visit to State of Yap (Federated States of Micronesia) andRepublic of Palau 3-8 June 1990 Department of Scientificand Industrial Research Auckland New Zealand 14 pp
HOOPER DJ amp EVANS K (1993) Extraction identificationand control of plant nematodes In Evans K TrudgillDL amp Webster JM (Eds) Plant parasitic nematodes intemperate agriculture Wallingford UK CABI Publishingpp 31-59
JACKSON GVH (1987) Corm rot of Cyrtosperma in GuamReport to Federated States of Micronesia and Palau
KOSHY PK JASY T MATHEW J amp NAMPOOTHIRICK (1991) Morphometric variability in Radopholus similisIndian Journal of Nematology 21 24-38
NAKANO K (1999) The supply of energy-source foodstuffs inthe Yap Islands a preliminary report Kagoshima UniversityResearch Center for the Pacific Islands 13 pp
NETSCHER C amp SEINHORST JW (1969) Propionic acidbetter than acetic acid for killing nematodes Nematologica15 286
ONJO M TAURA S amp SAKAMAKI Y (2001) The presentsituation of agriculture in Yap In Aoyama T (Ed) Progressreport of the 1999 survey of the research project lsquoSocialhomeostasis of small islands in an island-zonersquo KagoshimaUniversity Center for the Pacific Islands Occasional PapersNo 34 pp 91-93
RYSS AY amp WOUTS WM (1997) The genus Radopholus(Nematoda Pratylenchidae) from native vegetation in NewZealand with descriptions of two new species InternationalJournal of Nematology 7 1-17
TSANG MMC HARA AH amp SIPES BS (2003) Hot-water treatments of potted palms to control the burrowingnematode Radopholus similis Crop Protection 22 589-593
VALETTE C MOUNPORT D NICOLE M SARAH J-L ampBAUJARD P (1998) Scanning electron microscope study oftwo African populations of Radopholus similis (NematodaPratylenchidae) and proposal of R citrophilus as a juniorsynonym of R similis Fundamental and Applied Nematology21 139-146
636 Nematology
Corm rot of giant swamp taro
Table 1 Morphometrics of adult Radopholus similis from Yap Island All measurements are in microm and in the form mean plusmn standarddeviation (range)
Female Male
n 23 11L 604 plusmn 54 (503-726) 586 plusmn 542 (454-646)a 26 plusmn 34 (21-311) 328 plusmn 46 (235-40)b 74 plusmn 07 (59-88) 73 plusmn 07 (61-84)b1 45 plusmn 03 (38-5) 54 plusmn 03 (49-59)c 87 plusmn 07 (78-108) 8 plusmn 06 (65-84)c1 41 plusmn 04 (34-46) 52 plusmn 02 (49-57)o 201 plusmn 36 (13-267) ndashV 57 plusmn 16 (53-595) ndashDGO 3 plusmn 05 (2-4) ndashOV1 23 plusmn 51 (19-43) ndashOV2 21 plusmn 29 (17-29) ndashStylet length 165 plusmn 05 (15-17) ndashMetenchium length 8 plusmn 04 (8-85) ndashTelenchium length 85 plusmn 05 (8-9) ndashStylet knob height 2 plusmn 03 (15-25) ndashStylet knob width 35 plusmn 03 (3-45) ndashMedian bulb length 125 plusmn 11 (11-14) 11 plusmn 14 (8-13)Median bulb diam 95 plusmn 11 (8-125) 5 plusmn 05 (45-6)Lip region diam 95 plusmn 06 (8-10) 75 plusmn 06 (65-9)Lip region height 35 plusmn 04 (25-4) 55 plusmn 04 (5-6)Pharynx length 135 plusmn 88 (119-156) 1095 plusmn 116 (94-1285)Pharynx gland length 53 plusmn 9 (37-66) 305 plusmn 83 (165-42)Excretory pore from anterior end 875 plusmn 65 (69-99) 92 plusmn 84 (80-120)Diam at midbody 235 plusmn 49 (16-33) 18 plusmn 2 (155-205)Diam at excretory pore 21 plusmn 22 (175-26) 16 plusmn 06 (55-17)Diam at anus 165 plusmn 22 (13-22) 14 plusmn 03 (135-15)Diam at start of hyaline part 6 plusmn 05 (5-75) 5 plusmn 08 (45-65)Annulus width 15 plusmn 02 (1-2) 13 plusmn 02 (1-15)Lateral field width 65 plusmn 1 (55-9) 5 plusmn 07 (4-6)Tail length 68 plusmn 6 (53-77) 73 plusmn 3 (695-79)Number of tail annuli 52 plusmn 45 (44-60) ndashh 10 plusmn 18 (7-14) 9 plusmn 17 (65-115)Spiculum length ndash 215 plusmn 09 (20-23)Gubernaculum length ndash 11 plusmn 04 (10-12)
from 3 years after planting thus giving ample time forthe nematodes to become established in large populationdensities inside the corms The end result of nematodeinfection is the formation of shallow to deep cavitiesof dead tissues that advance towards the edible centralportion of the corm (Fig 2C) Infection is visible on theexternal surface of the corm as a perforated appearance ofthe otherwise smooth corm (Fig 2D) This damage highlyreduces the market quality of the corm
The widespread occurrence of the disease and the typeof damage R similis causes to the corms pose a serious
threat to giant swamp taro production food security andthe continuation of traditional customs on those islandswhere R similis occurs
Up to 50 000 R similis juveniles females and maleswere extracted from 10 g of fresh corm A stereoscanmicroscopy study revealed the high population densitiesof R similis inside the corm tissues Interestingly inaddition to R similis several specimens of a largeunidentified dorylaimid were also observed It is possiblethat this nematode species is a predator feeding on thenumerous juvenile and adult R similis The occurrence
Vol 7(4) 2005 633
VK Murukesan et al
Fig 1 Radopholus similis A Anterior part of female body B Anterior part of male body C Female vulval area with twospermathecae of equal size D Male tail E Female tail F-H Tail tip variations in female I Male lateral field at midbody J-LTail tip variations in male M Female lateral field at midbody (Scale bar A-M = 20 microm)
of concentrations of R similis eggs indicates that thisnematode species can reproduce inside the corm and maysuggest that R similis spends its entire life cycle insidethe giant swamp taro plant tissue thereby avoiding theanaerobic conditions of the flooded swamp AlthoughR similis has a been reported from many islands inthe Pacific and from many host plants including taro(Colocasia esculenta (L) Schott) and yam (Dioscoreaspp ie see Bridge 1988) the occurrence of thisnematode species in a swamp environment is uncommonand has not been reported previously If our hypothesisthat R similis does not occur in the rhizosphere ofthe plants is correct planting nematode-free cormlets
could prevent the spread of the disease In giant swamptaro new cormlets develop from the outer surface ofthe mother corms as side shoots approximately 1-2years after planting At harvest the cormlets are cut offclose to the point of attachment with the mother cormsCurrently excised cormlets are the only type of plantingmaterial used in Yap Nematode-free cormlets could beproduced via in vitro micropropagation and nematode-infected cormlets could be disinfected via heat treatmentThermotherapy has proven effective in eliminating Rsimilis from infected palms and Anthurium (Tsang et al2003 Arcinas et al 2004)
634 Nematology
Corm rot of giant swamp taro
Fig 2 A 9-year-old infected corm with wet loose mass of brown dead tissue (scale bar = 3 cm) B 2-year-old infected corm cutsuperficial diagonally showing the deep brown necrotic centre (arrow) (scale bar = 1 cm) C 8-year-old infected corm cut in halfshowing cavities of dead tissues that advance towards the edible central portion of the corm (arrows) (scale bar = 2 cm) D Entireinfected corms showing the perforated appearance of the otherwise smooth corm (scale bar = 2 cm)
Acknowledgements
Dr Singeru Singeo Executive Director College ofMicronesia-Land Grant Program and Mrs Kenye Killin
CES Assistant Director College of Micronesia-FSMKosrae Campus are gratefully acknowledged for thefinancial assistance provided from ADAP and USDA-IPM grants respectively Mrs NH Buckley of the PlantProtection Research Institute is thanked for technicalassistance
Vol 7(4) 2005 635
VK Murukesan et al
References
ARCINAS AC SIPES BS HARA AH amp TSANGMMC (2004) Hot water drench treatments for the con-trol of Radopholus similis in Rhapis and fishtail palmsHortScience 39 578-579
BRIDGE J (1988) Plant-parasitic nematode problems in thePacific Islands Journal of Nematology 20 173-183
ELBADRI GAA GERAERT E amp MOENS M (1999a)Morphological differences among Radopholus populations(Nematoda Tylenchida) from banana in Africa Journal ofNematode Morphology and Systematics 2 7-16
ELBADRI GAA GERAERT E amp MOENS M (1999b)Morphological differences among Radopholus similis (Cobb1893) Thorne 1949 populations Russian Journal of Nemato-logy 7 139-153
ENGLBERGER L SCHIERLE J MARKS JC amp FITZGER-ALD MH (2003) Micronesian banana taro and otherfoods newly recognized sources of provitamin A and othercarotenoids Journal of Food Composition and Analysis 163-19
GRANDISON GS (1990) Investigation of a nematode disorderof giant swamp taro (Cyrtosperma chamissonis) Report ona visit to State of Yap (Federated States of Micronesia) andRepublic of Palau 3-8 June 1990 Department of Scientificand Industrial Research Auckland New Zealand 14 pp
HOOPER DJ amp EVANS K (1993) Extraction identificationand control of plant nematodes In Evans K TrudgillDL amp Webster JM (Eds) Plant parasitic nematodes intemperate agriculture Wallingford UK CABI Publishingpp 31-59
JACKSON GVH (1987) Corm rot of Cyrtosperma in GuamReport to Federated States of Micronesia and Palau
KOSHY PK JASY T MATHEW J amp NAMPOOTHIRICK (1991) Morphometric variability in Radopholus similisIndian Journal of Nematology 21 24-38
NAKANO K (1999) The supply of energy-source foodstuffs inthe Yap Islands a preliminary report Kagoshima UniversityResearch Center for the Pacific Islands 13 pp
NETSCHER C amp SEINHORST JW (1969) Propionic acidbetter than acetic acid for killing nematodes Nematologica15 286
ONJO M TAURA S amp SAKAMAKI Y (2001) The presentsituation of agriculture in Yap In Aoyama T (Ed) Progressreport of the 1999 survey of the research project lsquoSocialhomeostasis of small islands in an island-zonersquo KagoshimaUniversity Center for the Pacific Islands Occasional PapersNo 34 pp 91-93
RYSS AY amp WOUTS WM (1997) The genus Radopholus(Nematoda Pratylenchidae) from native vegetation in NewZealand with descriptions of two new species InternationalJournal of Nematology 7 1-17
TSANG MMC HARA AH amp SIPES BS (2003) Hot-water treatments of potted palms to control the burrowingnematode Radopholus similis Crop Protection 22 589-593
VALETTE C MOUNPORT D NICOLE M SARAH J-L ampBAUJARD P (1998) Scanning electron microscope study oftwo African populations of Radopholus similis (NematodaPratylenchidae) and proposal of R citrophilus as a juniorsynonym of R similis Fundamental and Applied Nematology21 139-146
636 Nematology
VK Murukesan et al
Fig 1 Radopholus similis A Anterior part of female body B Anterior part of male body C Female vulval area with twospermathecae of equal size D Male tail E Female tail F-H Tail tip variations in female I Male lateral field at midbody J-LTail tip variations in male M Female lateral field at midbody (Scale bar A-M = 20 microm)
of concentrations of R similis eggs indicates that thisnematode species can reproduce inside the corm and maysuggest that R similis spends its entire life cycle insidethe giant swamp taro plant tissue thereby avoiding theanaerobic conditions of the flooded swamp AlthoughR similis has a been reported from many islands inthe Pacific and from many host plants including taro(Colocasia esculenta (L) Schott) and yam (Dioscoreaspp ie see Bridge 1988) the occurrence of thisnematode species in a swamp environment is uncommonand has not been reported previously If our hypothesisthat R similis does not occur in the rhizosphere ofthe plants is correct planting nematode-free cormlets
could prevent the spread of the disease In giant swamptaro new cormlets develop from the outer surface ofthe mother corms as side shoots approximately 1-2years after planting At harvest the cormlets are cut offclose to the point of attachment with the mother cormsCurrently excised cormlets are the only type of plantingmaterial used in Yap Nematode-free cormlets could beproduced via in vitro micropropagation and nematode-infected cormlets could be disinfected via heat treatmentThermotherapy has proven effective in eliminating Rsimilis from infected palms and Anthurium (Tsang et al2003 Arcinas et al 2004)
634 Nematology
Corm rot of giant swamp taro
Fig 2 A 9-year-old infected corm with wet loose mass of brown dead tissue (scale bar = 3 cm) B 2-year-old infected corm cutsuperficial diagonally showing the deep brown necrotic centre (arrow) (scale bar = 1 cm) C 8-year-old infected corm cut in halfshowing cavities of dead tissues that advance towards the edible central portion of the corm (arrows) (scale bar = 2 cm) D Entireinfected corms showing the perforated appearance of the otherwise smooth corm (scale bar = 2 cm)
Acknowledgements
Dr Singeru Singeo Executive Director College ofMicronesia-Land Grant Program and Mrs Kenye Killin
CES Assistant Director College of Micronesia-FSMKosrae Campus are gratefully acknowledged for thefinancial assistance provided from ADAP and USDA-IPM grants respectively Mrs NH Buckley of the PlantProtection Research Institute is thanked for technicalassistance
Vol 7(4) 2005 635
VK Murukesan et al
References
ARCINAS AC SIPES BS HARA AH amp TSANGMMC (2004) Hot water drench treatments for the con-trol of Radopholus similis in Rhapis and fishtail palmsHortScience 39 578-579
BRIDGE J (1988) Plant-parasitic nematode problems in thePacific Islands Journal of Nematology 20 173-183
ELBADRI GAA GERAERT E amp MOENS M (1999a)Morphological differences among Radopholus populations(Nematoda Tylenchida) from banana in Africa Journal ofNematode Morphology and Systematics 2 7-16
ELBADRI GAA GERAERT E amp MOENS M (1999b)Morphological differences among Radopholus similis (Cobb1893) Thorne 1949 populations Russian Journal of Nemato-logy 7 139-153
ENGLBERGER L SCHIERLE J MARKS JC amp FITZGER-ALD MH (2003) Micronesian banana taro and otherfoods newly recognized sources of provitamin A and othercarotenoids Journal of Food Composition and Analysis 163-19
GRANDISON GS (1990) Investigation of a nematode disorderof giant swamp taro (Cyrtosperma chamissonis) Report ona visit to State of Yap (Federated States of Micronesia) andRepublic of Palau 3-8 June 1990 Department of Scientificand Industrial Research Auckland New Zealand 14 pp
HOOPER DJ amp EVANS K (1993) Extraction identificationand control of plant nematodes In Evans K TrudgillDL amp Webster JM (Eds) Plant parasitic nematodes intemperate agriculture Wallingford UK CABI Publishingpp 31-59
JACKSON GVH (1987) Corm rot of Cyrtosperma in GuamReport to Federated States of Micronesia and Palau
KOSHY PK JASY T MATHEW J amp NAMPOOTHIRICK (1991) Morphometric variability in Radopholus similisIndian Journal of Nematology 21 24-38
NAKANO K (1999) The supply of energy-source foodstuffs inthe Yap Islands a preliminary report Kagoshima UniversityResearch Center for the Pacific Islands 13 pp
NETSCHER C amp SEINHORST JW (1969) Propionic acidbetter than acetic acid for killing nematodes Nematologica15 286
ONJO M TAURA S amp SAKAMAKI Y (2001) The presentsituation of agriculture in Yap In Aoyama T (Ed) Progressreport of the 1999 survey of the research project lsquoSocialhomeostasis of small islands in an island-zonersquo KagoshimaUniversity Center for the Pacific Islands Occasional PapersNo 34 pp 91-93
RYSS AY amp WOUTS WM (1997) The genus Radopholus(Nematoda Pratylenchidae) from native vegetation in NewZealand with descriptions of two new species InternationalJournal of Nematology 7 1-17
TSANG MMC HARA AH amp SIPES BS (2003) Hot-water treatments of potted palms to control the burrowingnematode Radopholus similis Crop Protection 22 589-593
VALETTE C MOUNPORT D NICOLE M SARAH J-L ampBAUJARD P (1998) Scanning electron microscope study oftwo African populations of Radopholus similis (NematodaPratylenchidae) and proposal of R citrophilus as a juniorsynonym of R similis Fundamental and Applied Nematology21 139-146
636 Nematology
Corm rot of giant swamp taro
Fig 2 A 9-year-old infected corm with wet loose mass of brown dead tissue (scale bar = 3 cm) B 2-year-old infected corm cutsuperficial diagonally showing the deep brown necrotic centre (arrow) (scale bar = 1 cm) C 8-year-old infected corm cut in halfshowing cavities of dead tissues that advance towards the edible central portion of the corm (arrows) (scale bar = 2 cm) D Entireinfected corms showing the perforated appearance of the otherwise smooth corm (scale bar = 2 cm)
Acknowledgements
Dr Singeru Singeo Executive Director College ofMicronesia-Land Grant Program and Mrs Kenye Killin
CES Assistant Director College of Micronesia-FSMKosrae Campus are gratefully acknowledged for thefinancial assistance provided from ADAP and USDA-IPM grants respectively Mrs NH Buckley of the PlantProtection Research Institute is thanked for technicalassistance
Vol 7(4) 2005 635
VK Murukesan et al
References
ARCINAS AC SIPES BS HARA AH amp TSANGMMC (2004) Hot water drench treatments for the con-trol of Radopholus similis in Rhapis and fishtail palmsHortScience 39 578-579
BRIDGE J (1988) Plant-parasitic nematode problems in thePacific Islands Journal of Nematology 20 173-183
ELBADRI GAA GERAERT E amp MOENS M (1999a)Morphological differences among Radopholus populations(Nematoda Tylenchida) from banana in Africa Journal ofNematode Morphology and Systematics 2 7-16
ELBADRI GAA GERAERT E amp MOENS M (1999b)Morphological differences among Radopholus similis (Cobb1893) Thorne 1949 populations Russian Journal of Nemato-logy 7 139-153
ENGLBERGER L SCHIERLE J MARKS JC amp FITZGER-ALD MH (2003) Micronesian banana taro and otherfoods newly recognized sources of provitamin A and othercarotenoids Journal of Food Composition and Analysis 163-19
GRANDISON GS (1990) Investigation of a nematode disorderof giant swamp taro (Cyrtosperma chamissonis) Report ona visit to State of Yap (Federated States of Micronesia) andRepublic of Palau 3-8 June 1990 Department of Scientificand Industrial Research Auckland New Zealand 14 pp
HOOPER DJ amp EVANS K (1993) Extraction identificationand control of plant nematodes In Evans K TrudgillDL amp Webster JM (Eds) Plant parasitic nematodes intemperate agriculture Wallingford UK CABI Publishingpp 31-59
JACKSON GVH (1987) Corm rot of Cyrtosperma in GuamReport to Federated States of Micronesia and Palau
KOSHY PK JASY T MATHEW J amp NAMPOOTHIRICK (1991) Morphometric variability in Radopholus similisIndian Journal of Nematology 21 24-38
NAKANO K (1999) The supply of energy-source foodstuffs inthe Yap Islands a preliminary report Kagoshima UniversityResearch Center for the Pacific Islands 13 pp
NETSCHER C amp SEINHORST JW (1969) Propionic acidbetter than acetic acid for killing nematodes Nematologica15 286
ONJO M TAURA S amp SAKAMAKI Y (2001) The presentsituation of agriculture in Yap In Aoyama T (Ed) Progressreport of the 1999 survey of the research project lsquoSocialhomeostasis of small islands in an island-zonersquo KagoshimaUniversity Center for the Pacific Islands Occasional PapersNo 34 pp 91-93
RYSS AY amp WOUTS WM (1997) The genus Radopholus(Nematoda Pratylenchidae) from native vegetation in NewZealand with descriptions of two new species InternationalJournal of Nematology 7 1-17
TSANG MMC HARA AH amp SIPES BS (2003) Hot-water treatments of potted palms to control the burrowingnematode Radopholus similis Crop Protection 22 589-593
VALETTE C MOUNPORT D NICOLE M SARAH J-L ampBAUJARD P (1998) Scanning electron microscope study oftwo African populations of Radopholus similis (NematodaPratylenchidae) and proposal of R citrophilus as a juniorsynonym of R similis Fundamental and Applied Nematology21 139-146
636 Nematology
VK Murukesan et al
References
ARCINAS AC SIPES BS HARA AH amp TSANGMMC (2004) Hot water drench treatments for the con-trol of Radopholus similis in Rhapis and fishtail palmsHortScience 39 578-579
BRIDGE J (1988) Plant-parasitic nematode problems in thePacific Islands Journal of Nematology 20 173-183
ELBADRI GAA GERAERT E amp MOENS M (1999a)Morphological differences among Radopholus populations(Nematoda Tylenchida) from banana in Africa Journal ofNematode Morphology and Systematics 2 7-16
ELBADRI GAA GERAERT E amp MOENS M (1999b)Morphological differences among Radopholus similis (Cobb1893) Thorne 1949 populations Russian Journal of Nemato-logy 7 139-153
ENGLBERGER L SCHIERLE J MARKS JC amp FITZGER-ALD MH (2003) Micronesian banana taro and otherfoods newly recognized sources of provitamin A and othercarotenoids Journal of Food Composition and Analysis 163-19
GRANDISON GS (1990) Investigation of a nematode disorderof giant swamp taro (Cyrtosperma chamissonis) Report ona visit to State of Yap (Federated States of Micronesia) andRepublic of Palau 3-8 June 1990 Department of Scientificand Industrial Research Auckland New Zealand 14 pp
HOOPER DJ amp EVANS K (1993) Extraction identificationand control of plant nematodes In Evans K TrudgillDL amp Webster JM (Eds) Plant parasitic nematodes intemperate agriculture Wallingford UK CABI Publishingpp 31-59
JACKSON GVH (1987) Corm rot of Cyrtosperma in GuamReport to Federated States of Micronesia and Palau
KOSHY PK JASY T MATHEW J amp NAMPOOTHIRICK (1991) Morphometric variability in Radopholus similisIndian Journal of Nematology 21 24-38
NAKANO K (1999) The supply of energy-source foodstuffs inthe Yap Islands a preliminary report Kagoshima UniversityResearch Center for the Pacific Islands 13 pp
NETSCHER C amp SEINHORST JW (1969) Propionic acidbetter than acetic acid for killing nematodes Nematologica15 286
ONJO M TAURA S amp SAKAMAKI Y (2001) The presentsituation of agriculture in Yap In Aoyama T (Ed) Progressreport of the 1999 survey of the research project lsquoSocialhomeostasis of small islands in an island-zonersquo KagoshimaUniversity Center for the Pacific Islands Occasional PapersNo 34 pp 91-93
RYSS AY amp WOUTS WM (1997) The genus Radopholus(Nematoda Pratylenchidae) from native vegetation in NewZealand with descriptions of two new species InternationalJournal of Nematology 7 1-17
TSANG MMC HARA AH amp SIPES BS (2003) Hot-water treatments of potted palms to control the burrowingnematode Radopholus similis Crop Protection 22 589-593
VALETTE C MOUNPORT D NICOLE M SARAH J-L ampBAUJARD P (1998) Scanning electron microscope study oftwo African populations of Radopholus similis (NematodaPratylenchidae) and proposal of R citrophilus as a juniorsynonym of R similis Fundamental and Applied Nematology21 139-146
636 Nematology