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whitefly as vector

whitefly as vector,whitefly species, biotypes of whitefly, types of virus, virus-vector relationship,insect act as vector, major crop disease, transmission of virus by whitefly and management of whitefly.

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whitefly as vector

  1. 1. Presented by Bharat S Borude M.Sc(Agri)Entomology PG15-ENT1587 Seminar Incharge Dr. D. B. Undirwade Head Department of Entomology Dr. P.D.K.V. Akola Chairman : Dr. S.K. Bhalkare Assistant professor Department of Entomology Dr.PDKV Akola
  2. 2. Whitefly  The whitefly was first reported in Greece 125 years ago.  It became a major pest on cotton in India only after 1984.  Whitefly feeds on more than 500 plant species and transmits a range of viral diseases in plants. Taxonomic position Kingdom : Animalia Phylum : Arthropoda Class : Insecta Order : Hemiptera Family : Aleyrodidae Genus : Bemisia Species : tabaci  1550 species recorded Source : Wikipedia
  3. 3.  Insect vectors of plant viruses are found in 7 orders of the class Insecta.  The majority of vectors are found in the two orders of insects with pierce-sucking mouthparts (number of species in parenthesis): Hemiptera (300) and Thysanoptera (6).  Other vector species are found in five orders of chewing insects: Coleoptera (30), Orthoptera (10), Lepidoptera (4), Diptera (2) and Dermaptera (1).  Over 1300 whitefly species in over 120 genera have been described with only the Bemisia and Trialeurodes genera being virus vectors.  There are 3 important species. About 114 viruses are transmitted by these 3 spp.  Bemisia tabaci -108 viruses  Trialeurodes vaporariorum -3 viruses  Trialeurodes abutilonea -3 viruses (Mound and Halsey, 1978)and )(Fereres and Raccah, 2015)
  4. 4. 1) Greenhouse whitefly - Trialeurodes vaporariorum 2) Sweet potato whitefly - Bemisia tabaci 3) Bandedwing whitefly - Trialeurodes abutilonea Common whitefly species Source : Wikipedia
  5. 5. Whitefly species identification species egg nymphs adult T. vaporariorum GHWF SPWF B. tabaci Source : Google Image (Wikipedia)
  6. 6. Biotypes of B. tabaci. host associations, and virus transmission UYV, = lettuce infectious yellows virus; AGMV, Asystasia golden mosaic virus; TYLCV·Ye, tomato yellowleaf curl virus, Yemen; JMV, Jatropha mosaic virus; ACMV, African cassava mosaic virus. Brown et.al.1995.
  7. 7. LIFE CYCLE OF WHITEFLY yellowish white Source : Wikipedia
  8. 8.  Under surface of the leaves  Both nymphs and adults  Needle like mouthparts - vascular tissue / phloem  Suck the plant sap.  Excreting honey dew on which sooty mould grows. NATURE OF DAMAGE Whitefly adults Whitefly nymphs
  9. 9. •During 2015-16 an epidemic of whitefly incidence was noticed during August in the cotton growing areas of Haryana, Punjab and Rajasthan. •In 2015-16, Punjab had 4.50 lakh hectares under cotton crop. The drop in acreage is a massive 43.11% in just one year with wary farmers shifting to other crops. •The crop loss due to this is estimated at 40-50 per cent of the total or 1.5 to two million bales (a bale is 170 kg). (http://timesofindia.indiatimes.com/city/chandigarh/WhiteflyfearCottonacreagedrops- to61yearlow/articleshowprint/53135445.cms?null) ECONOMIC LOSSES DUE TO WHITEFLIES
  10. 10. (The Hindu,October 18,2015)
  11. 11. Vector  Definition: A vector is any agent (microorganism) that carries and transmits an infectious pathogen into another living organism. FACTS of Transmission of Plant Viruses  Plant viruses do not penetrate the intact plant cuticle.  Not disseminated as such by wind or water, and even when they are carried in plant sap or debris  Generally do not cause infections unless they come in contact with the contents of wounded living cell 1. Mechanical contact 2. Grafting 3. Vegetative propagation 4. Botanical (sexual) seed 5. Pollen Source: (Fereres and Raccah, 2015)
  12. 12. The Importance of Insect Vectors Most plant viruses depend on vectors for their survival for two principal reasons:  An impermeable cuticle coats the plant epidermis preventing entry of virus particles (animal viruses enter readily through natural openings). Most vectors are insects. Several plant viruses may spread by contact or vegetative reproduction. Many insects such as hemipterans are well adapted to their role as vectors by their capacity to pierce the epidermis and delicately deposit the virus in the cytoplasm without risking the integrity of the plant cell. Recent findings propose that viruses have adapted to their vectors modifying their behaviour to maximise their own spread.  Plants are rooted and lack independent mobility. Therefore, many viruses depend on insects for transport among hosts (unlike animals that, by their own mobility, transport the virus to new niches). Sorce: (Fereres and Raccah, 2015)
  13. 13. Types of viruses based upon the action of vector  Stylet-borne viruses(non-persistent)  The association occurs within the feeding apparatus of the insect, where the virus can be rapidly adsorbed and then released into a different plant cell. The feeding insect looses the virus rapidly when feeding on a non- infected plant.  Cucumoviruses, carlaviruses and potyviruses  Circulative viruses(semi-persistent)  Circulate through the tissues of the vectors. Not transmitted immediately after the acquisition but the vectors have to wait several hours  Maize chlorotic dwarf virus,rice tungro virus,potato leaf-roll virus.  Propagative viruses(persistent)  Viruses start multiplying within their vectors and establish a biological relationship viruses possess an incubation period. Almost all leafhopper transmitted viruses are propagative. Vector remain viruliferous throughout their life.  Wheat streak mosaic virus. Source: (Whitfield and Rotenberg (2015)
  14. 14. Virus-Vector Relationship  Non-circulative viruses are retained in the insect stylet (A) or foregut (B).  Non-propagative circulative (yellow circles) viruses are generally phloem limited and penetrate the insect body via the midgut or hindgut.  Circulative viruses use a hemolymph route to reach the salivary glands.  In contrast, circulative propagative viruses (red ovals) enter the insect at the anterior region of the midgut and/or filter chamber region.  Propagative viruses may use a hemolymph route and others such as the Rhabdoviruses also use a neurotropic route to reach the salivary glands.  Propagative viruses replicate in the midgut cells and other insect tissues. Source: (Whitfield and Rotenberg (2015)
  15. 15.  The salivary glands are the final destination for circulative transmission, and viruses reach the salivary glands via the hemolymph or other routes such as the nervous tissue (neurotropic route) or through connective tissues.  Reoviruses use tubules to move cell to cell in the midgut and another uses the tubular structure to traverse the basal lamina (C).  Insets: Magnification of an insect stylet showing the proposed site of virion attachment at the tip of the stylet in the common duct region (A).  Numbers designate the different strategies for virion binding and retention in the stylet: capsid strategy, direct binding of capsid protein to the stylet (1), helper component strategies for caulimoviruses, two virus proteins serve as a “bridge” between the virion and the stylet (2) and potyviruses, one virus protein (HC-Pro) binds to the aphid stylet and to the virus (3). Source: (Whitfield and Rotenberg (2015)
  16. 16.  Inset B: Magnification of the foregut retention site and proposed capsid binding strategy used by Criniviruses. The minor capsid protein (CPm) is the viral attachment protein.  Inset C: The steps in the reovirus infection cycle and spread to adjacent cells modeled on Rice dwarf virus. Rice dwarf virus enters cells using the endocytic pathway and after virion release from the vesicle the replication cycle begins.  Progeny virions move cell-to-cell via tubule structures composed of virus nonstructural protein. This enables virions to move directly from one cell to another without an extracellular phase. (Whitfield and Rotenberg (2015)
  17. 17. Insects act as vector are………  Aphid  Whitefly  Hopper  Thrips  Mites (non insect)  Others (psylla, leaf miner )
  18. 18. • Leaf curl of chilli • Bud necrossis of groundnut • Wheat streak mosaic • Sterility mosaic of tur • Rice tungro virus (Nephotatix viruscens) • Maize streak virus • Bunchy top of banana (Apentelus sp) • Papaya mosaic • Potato leaf roll virus • Citrus tristeza virus Source: Applied Entomology (book) and wikipedia
  19. 19. Citrus psylla (Diphorina citri) Citrus greening (Mycoplasma) Leaf miner (Phyllocnistis citrella) Citrus canker (Bacteria) Source: Applied Entomology (book) and wikipedia
  20. 20. Whitefly transmitting viruses Geminivirus (Begamovirus) Crinivirus Closterovirus (www.planthealthaustralia.com.au/go/p hau/biosecurity/general-biosecurity- information).
  21. 21. Whitefly Tomato leaf curl virus Cotton leaf curl virus Bhendi yellow vein mosaic virus A) Geminivirus (Begamovirus) Source: Plant health Australia PHA & NGIA | Contingency Plan – Whitefly transmitted viruses oct. 2010
  22. 22. Mung bean yellow mosaic virus Soybean crinkle leaf virus Cabbage leaf curl virus A) Geminivirus (Begamovirus) Source: Plant health Australia PHA & NGIA | Contingency Plan – Whitefly transmitted viruses oct. 2010
  23. 23. Cucumber yellows virus Lettuce chlorosis virus Tomato chlorosis virus B)Crinivirus Source: Plant health Australia PHA & NGIA | Contingency Plan – Whitefly transmitted viruses oct. 2010
  24. 24. Grapevine corky bark-associated virus Little cherry virus 1 Sugarcane mild mosaic virus C)Closterovirus Source: Plant health Australia PHA & NGIA | Contingency Plan – Whitefly transmitted viruses oct. 2010
  25. 25. Leaf Curl of Cotton  Leaves of infected cotton curl upward and bear leaf-like enations on the underside along with vein thickening.  Leaves curl upwards and the plant vigour reduces. Leaves become shiny with honeydew or darkened by sooty mould growing on honeydew.  Lint contamination with honeydew and associated fungi occur during heavy infestations after boll opening. Source: www.cicr.in
  26. 26. Yellow Vein Mosaic of okra Yellowing of the entire network of veins in the leaf blade is the characteristic symptom. In severe infections the younger leaves turn yellow, become reduced in size and the plant is highly stunted. Infection may start at any stage of plant growth. Source: Wikipedia
  27. 27.  The most common indicator of the disease is the yellowing and upward curling of the leaves, which may also appear crumply.  Plant growth soon becomes stunted and may even take on a bush-like growth habit.  Flowers usually will not develop and those that do simply drop off. In addition, fruit production will be significantly reduced.  TYLCV is transmitted exclusively by the whitefly Bemisia tabaci. Soruce: Castillo et.al.2011
  28. 28. Management of whitefly  Judicious application of N fertilizers  Grow inter crops and trap crops like BG, GG, soybean cluster bean cowpea and groundnut with cotton and grow castor and tomato as trap crops as border crops  Destroy the infested plants and weeds surrounding the field  Erect the yellow sticky traps 10-12/ha or keeping yellow empty tins smeared with grease as trap. Wipe out trapped whiteflies every day and apply grease again  Destroy the different stages of the insect by collecting the infested leaves and affected parts of the plant by polythene covers to avoid contact with other plants  Natural enemies like mirid bug and spiders
  29. 29.  Seed treatment -Carbosulfan - 40 g/kg, Imidacloprid 70 WS - 5 g/kg and Thiamethoxam 70 WS - 4 g/kg  Soil application- Carbofuran 3G 12 – 14 kg/ac or Phorate 10G 4 – 5 kg/ac nearer to the base of seedlings when the soil is moist  Stem application-Monocrotophos or methyl demeton 1:4 with water Imidacloprid 200 SL 1: 20 with water 20 – 25, 30 – 35 and 40 – 45 DAS  Foliar spray: Azadirachtin 0.15% W/W 2.5l-5.0l Azadirachtin 5% W/W 750 ml/ha Difenthiauron 50SC 300gm/ha Buprofezin 25% SC 1000ml/ha Carbaryl 85% W.P. 1411 ml/ha Dimethoate 30% EC 990 ml/ha Monocrotophos 36% SL 375 ml/ha Oxydemeton – methyl 25% EC 1000 ml Phosphamidon 40% SL 625-750 ml/ha Spiromesifen 22.9% SC 600ml/ha Thiacloprid 21.7% SC 500-600 ml/ha Imidacloprid 17.8% SL 100-125 Source: Applied Entomology
  30. 30. NBRI developed whitefly resistant transgenic Cotton  The team of scientists isolated an anti-whitefly gene named TMA12 from an edible fern Tectaria sp.. This fern has been maintained in NBRI garden for the past 50 years.  One of the proteins was isolated from an edible fern Tectaria sp, which is lethal to Whitefly and interferes in its reproductive process.  This fern’s anti - whitefly protein was introduced in cotton to translate the potential of protein into a technology.  The selected transgenic cotton lines shows remarkable control of whitefly population through several generation. Pradhymna Singh with whitefly resistant transgenic cotton plants. Source: www.nbri.res.in
  31. 31. CONCLUSION Whitefly is a polyphagous, migratory and highly resistant pest. Synthetic organic pesticides caused resurgence of the pest leading to the death of the farmers recently occurred in Punjab and Haryana in India. Considering the economic importance of the pest, scientists and farmers have been taking profound practices to manage the whitefly including cultural, host plant resistance, biological and least importance to the older molecules which already developed resistance to the whitefly and including the newer molecules in a need based application. NBRI developed white fly resistant transgenic cotton. This gives farmers the hope that an overdose of fertilisers and pesticides would save the plant. But there is a need to develop transgenic crops which resist the sucking pest complex of different crops.
  32. 32. Reference  http://timesofindia.indiatimes.com/city/chandigarh/WhiteflyfearCottonacreage dropsto61yearlow/articleshowprint/53135445.cms?null.  http://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-leaves-curling.htm  Kranthi K. R.2015. Whitefly-the black story cotton statistic and news cotton association of India, no.15 www.cici.org.in.  Mound LA, Hasley SH (1978) Whitefly of the World, a systemic catalogue of the Aleyrodidae(Homoptera) with host plant and natural enemy data. British Museum (Natural History), London and John Wiley and Sons, Chichester UK.  Ng, J.C., Falk, B.W., 2006. Virus–vector interactions mediating nonpersistent and semipersistent transmission of plant viruses. Annu. Rev. Phytopathol. 44, 183–212.  Raccah B. and Fereres A. 2009.plant virus transmission by insects Encyclopedia of life science (ELS), Jhon Willey and sons, ltd. chichester .  Whitfield, A.E., Rotenberg, D., 2015. Disruption of insect transmission of plant viruses. Curr. Opin. Insect Sci.  www.nbri.res.in  www.wikipedia.com

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