1. ROLE OF INSECT VECTORS IN VIRUS DISEASE EPIDEMIOLOGY: Case from Nepalk
WEL-COME
workshop on the seed borne virus diseases of vegetable crops by IPM-IL
April 7-9, 2014
Himalaya Hotel, Lalitpur, Nepal.
Presented by:
RP Mainali, N Dangi, AR Ansari

2. Introduction
An organism capable of transmitting pathogens (viruses, bacteria, phytoplasma and fungi) from one host to another
Insect – by feeding on diseased plants by contact-acquire disease causing agents-transmit them to healthy plants (by contact, by contamination through soil or other biological agencies)
Both piercing and sucking mouthparts and chewing mouthparts are associated with virus transmission

3. Introduction contd…
Insect orders responsible for transmitting viruses comprises
Hemiptera (Aphids, leafhoppers, whiteflies, mealybugs etc.)- transmit 90% of plant diseases
Thysanoptera (Thrips)
Coleoptera (beetles)
Orthoptera (Grasshopper)
Dermaptera (earwigs)
Among, 850 described plant viruses
About half are transmitted by aphids (Main vectors are Myzus persicae, Aphis gossypii and A. cracivora)
About one third by leafhoppers
Some by mealybugs, whiteflies and thrips (Atwal and Dhaliwal, 2008)

4. Plant virus diseases, more prevalent and destructive in recent years
Introduction contd…
Plant virus diseases, more prevalent and destructive in recent years
Due to better recognition of virus diseases - lab, capacity building
Exchange of plant material from one place to another
Distribution of many insect vectors
For transmission of viruses – activity of vector and persistence of virus have vital role

5. Review of Research on Insect Vectors of Plant virus Diseases in Nepal

6. Virus and virus-like diseases are prevalent in the agricultural importance crop (Dahal 1984, Amatya & Manandhar 1986, Shrestha & Albrechtsen 1989, Dahal 1990, Regmi, 1994).
Crop productivity depleted by viruses and virus-like diseases (Dahal et al. 1988, Shrestha & Albrechtsen 1989, Dahal 1990).
Insect vector management work started (NARC annual report, ).

7. Aphids (Hemiptera: Homoptera: Aphidoidea)
More than 150 species of aphids are reported in Nepal (Thapa, 2000, Joshi & Manandhar 2000, Das and Raychaudhury 1983, Sharma 1981/82, Miyazaki, 1977)
Aphids on potato (Solanum tuberosum) transfer six important virus diseases in terai and midhill
Potato Virus A (PVA)
Potato Virus M (PVM)
Potato Carlavirus S (PVS)
Potato Potevirus X (PVX)
Potato Potyvirus Y (PVY)
Potato Leafroll Luteovirus (PLRV) (Akius & Kloos 1990)

8. Myzus persicae Sulzer ASSOCIATED WITH DIFFERENT PLANT VIRUSES IN NEPAL
Vector
Transmitted virus diseases
References
Myzus persicae Sulzer
Potato Potyvirus Y (PVY)
Ranjit et al. 1998
Potato Leaf Roll Luteovirus (PLRV)
Joshi 1979
PRSV-W, ZYMV, CMV, CABYV in cucurbits
Joshi and Manandhar 2000; Dahal et al. 1997; Joshi & Manandhar 2000
Bean Common Mosaic Virus (BCMV)
Joshi et al. 1993
Pea Seed-borne Mosaic Potyvirus (PSBMV)
Shrestha & Acbreehtsen 1989
Turnip Mosaic Virus in Rayo
Pradhanang & Ghimire 1993

9. Contd…
OTHER APHID SPECIES ASSOCIATED WITH DIFFERENT PLANT VIRUSES IN NEPAL
Vectors
Transmitted diseases
References
Aphids (Hemiptera: Aphidoidae)
Remarks
Aphis gossypii Glover
Cucumber Mosaic Cucumovirus (CMV)
Joshi 2003
Papaya Ringspot Potyvirus – watermelon strain (PRSV-W)
Dahal 1992
Zuchhini Yellow Mosaic Potyvirus (ZYMV)
Joshi & Manandhar 2000
Cucurbit Aphid-borne Yellow Luteovirus (CABYV)
Regmi et al. 1997
Citrus Tristeza Virus (CTV)
Rymi et al. 2000
Aphis craccivora Koch
CMV
Cowpea Aphid Borne Mosaic Potyvirus (CABMV)
Joshi and Manandhar 2000
Pea seed Borne Mosaic Potyvirus (PSBMV)
Joshi et al. 1993
Bean Cammon Mosaic Virus (BCMV)
Aulacorthum solani (Kalt.)
PVY (Potato virus Y), PLRV, CMV
Joshi 1979 Joshi & Manandhar 2000
Acyrthosiphon pisum (Harris)
PVY, CMV in cucumber
Aphis fabae (Scolopi)
PVY, CMV in tomato

10. Contd… Vectors Transmitted diseases References
Brachycaudus helichrysi (Kalt.)
PVY, CMV and tomato
Joshi 2003
Rhopalosiphum padi (Linn.)
PVY, PLRV in potato
Joshi 1979
Schizaphis graminum (Rondani)
PVY, CMV
Joshi & Manandhar 2000
Brevicoryne brassicae (Linn.)
CMV, PVY
Lipaphis erysimi (Kalt.)
TUMV in Rayo
Shreshta & Albrecalt Sen 1989
Toxoptera citricidus (Kirkaldy)
CTV
Knorr and Shah 1971
Toxoptera aurantii (Boyer de Fonscolombe)
Pentalonia nigronervosa Coq.
Chhirke and Furke diseases in Cardamom
Castop 1977
Banana Bunchy Top Virus (BBTV)
Ojha 1978, Dahal 1990
Rhopolosiphum maidis Fitch
PRS-W, ZYMV
Dahal 1992
Barley Yellow Hwert Luteo Virus (BYDR)
Sitobion avenae (Fab.)
BYDV in Gramminae
Thapa 2000

11. Whiteflies (Hemiptera: Homoptera: Aleyrodidae)
Whiteflies, Bemisia tabaci) is reported from Nepal (Vidal et al. 1997, Mainali 2012)
WHITEFLIES ASSOCIATED WITH DIFFERENT PLANT VIRUSES IN NEPAL
Vector
Transmitted virus disease
References
Remarks
Bemisia tabaci (Genn.)
Tomato Yellow Leaf Curl Geminivirus (TYLCV)
Joshi et al. 1997
Incidence in tomato and chilli
Okra Yellow Vein Mosaic Virus
Shrestha and Albrechtsen 1989
Common in terai and inner terai
Tobacco Leaf Curl Geminivirus (TobLCV)
NARSC 1989 ; Karna & Chaudhary 1999
Mung Bean Yellow Mosaic Geminivirus (MYMV)
Joshi et al. 2000

12. Leafhopper (Hemiptera: Homoptera: Cicadellidae
LEAFHOPPER ASSOCIATED WITH DIFFERENT PLANT VIRUSES IN NEPAL
Vectors
Transmitted diseases
References
Remarks
Leafhoppers – Cicadellidae
Nephotettix nigropictus (Stal)
Rice Dwarf Phytoreovirus (RDV)
Omura et al. 1982; John et al. 1979
Pest of rice (Dahal et al. 1997).
Nephotettix virescens (Distant)
Rice Tungro Bacilliform Badnavirus (RTBV)
Dahal et al. 1996
N. virescens associated with tungro disease at Parwanipur (John et al. 1979)
Rice Tungro Spherical Waikavirus (RTSV)

13. Thrips (Thysanoptera: Thripidae)
THRIPS SPECIES ASSOCIATED WITH DIFFERENT PLANT VIRUSES IN NEPAL
Vectors
Transmitted diseases
References
Remarks
Thysonaptera: Thripidae (Thrips)
Scirtothrips dorsalis Hood
Tomato Spotted Wilt Tospovirus (TSWV) known as bud necrosis disease (BND) in groundnut
Rao & Waliyar 1988; Shrestha & Albrechtsen 1989; Rao & Rao 1992; Thapa 1997
These Virus transmitting vectors associated with different crops in Nepal (Thapa 1997, Joshi & Manandhar 2000).
Thrips tabaci Linderman
TSWV known as BND in groundnut
Thapa 1997
Thrips palmi Karny

14. Thank You