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Thrips biology, economic importance and control strategies

Economic importance - thrips as pest

Thrips are a major constraint to a wide array of crops produced in Sub-Saharan Africa. Among the staple food crops, grain legumes such as cowpea, beans, dolichos are severly infested by thrips with yield losses ranging from 20 - 100% (Jackai and Daoust 1986; Timko and Singh 2008; Dugje et al. 2009). The bean flower thrips, Megalurothrips sjostedti is rated as one of the most important constraint to production of cowpea in Sub-Saharan Africa (Dugje et al. 2009). Among the high value vegetable crops produced for the domestic markets in Africa, onion, tomato, chillies, cabbage, kale are seriously constrained by thrips damage.

Figure 1. Some economically important thrips species observed in Eastern Africa key

Pest thrips
For eg. Yield losses due to thrips infestation can be up to 60% in onions (Waiganjo et al. 2008) and 24% in tomato (Kagezi et al, 2000). Similarly vegetables produced for the export markets such as French bean, capsicum, broccoli are severely infested by thrips. For eg. Yield losses due to thrips infestation in French beans can be as high as 68-70% (Nyasani et al. 2012). Among the fruits and plantation crops produced in Sub-Saharan Africa, crops such as avocado, citrus, coffee, tea, banana, cocoa are damaged by thrips (infonet-Biovision). Thrips especially western flower thrips are also a major biotic constraint to floriculture industry, affecting the quality of flower produced due to their feeding. Thrips like onion thrips and Western Flower thrips also transmit the tospoviruses like Iris yellow spot virus (IYSV) in onion and Tomato Spotted Wilt Virus (TSWV) in Tomato, respectively. TSWV can inflict up to 20 - 80% yield loss (Wangai et al. 2001; Ramkat et al. 2008; Rapando et al. 2009), while IYSV causes up to 75% leaf damage (Birithia et al. 2011). Thrips infestation also affects the quality of the produce especially in vegetables, fruits and flowers grown for export market. Due to their high relevance as quarantine pests their very presence in the produce also results in rejection at export destination countries.

Symptoms of thrips damage

Fig. 1

Figure 1

 Fig. 2

Figure 2

 Fig. 3

Figure 3

 Fig. 4

Figure 4

Fig. 5

Figure 5

 Fig. 6

Figure 6

 Fig. 7

Figure 7

 Fig. 8

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Fig. 9

Figure 9

 Fig. 10

Figure 10

 Fig. 11

Figure 11

 Fig. 12

Figure 12

Figures

White silvery specks on the leaves
Fig. 1: Onion
Fig. 2: Tomato
Fig. 3: Kale
Tip drying
Fig. 4: Onion
Brown rusty spots on leaves and fruit scarring
Fig. 5: French bean pods
Fig. 6: French bean leaves
Fig. 7: Cabbage leaves
Fig. 8: Banana fruits
Flower shedding and reduced pod set
Fig. 9: French bean pods
Discoloration/Deformation of flowers and leaves
Fig. 10: Healthy Chrysanthemum flower
Fig. 11: Damaged Chrysanthemum flower (Frankliniella occidentalis)
Fig. 12: Damaged Ficus benjamina leaf (Parthenothrips dracaenae)

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Bibliography and important links to thrips and tospoviruses

Amin PW, Reddy DVR, Ghanekar AM & Reddy MS (1981). Transmission of Tomato Spotted Wilt Virus, the causal agent of bud necrosis of peanut, by Scirtothrips dorsalis and Frankliniella schultzei. Plant Disease 65 (8): 663-665

Birithia R, Subramanian S, Pappu HR, Sseruwagi P, Muthomi JW & Narla RD (2011). First report of Iris Yellow spot virus infecting onion in Kenya and Uganda. Plant Disease 95: 1195

Birithia R, Subramanian S, Villinger J, Muthomi JW, Narla RD & Pappu HR (2012). First report of Tomato yellow ring virus (Tospovirus, Bunyaviridae) infecting tomato in Kenya. Plant Disease 96: 1384

Brittlebank, CC (1919). Tomato diseases. J Agric Vicotria 17: 231-235

Dugje IY, Omoigui LO, Ekeleme F, Kamara AY & Ajeigbe H (2009). Farmers- Guide to Cowpea Production in West Africa. IITA, Ibadan, Nigeria. 20 pp

German TL, Ullman DE, Moyer JW (1992). Tospoviruses: Diagnosis, molecular biology, phylogeny, and vector relationships. Annu Rev Phytopathol 30: 315–348

Jackai LEN & Daoust RA (1986). Insect Pests of Cowpeas. Annual Review of Entomology 31:95-119.

Jones DR (2005). Plant viruses transmitted by thrips. European Journal of Plant Pathology 113: 119-157

Milne, RG, Francki RI (1984). Should tomato spotted wilt virus be considered as a possible member of the family Bunyaviridae? Intervirology 22: 72-76

Moritz G, Kumm S, Mound LA (2004). Tospovirus transmission depends on thrips ontogeny. Virus Research 100: 143-149

Mound LA (1996). The Thysanoptera vector species of Tospoviruses. Acta Horticulturae 431: 298-309

Nagata T, Inoue-Nagata AK, Smid HM, Goldbach R, Peters D (1999). Tissue tropism related to vector competence of Frankliniella occidentalis for tomato spotted wilt tospovirus. J Gen Virol 80 (Pt 2): 507-515

Nyasani JO, Meyhöfer R, Subramanian S & Poehling H-M (2012). Effect of intercrops on thrips species composition and population abundance on French beans in Kenya. Entomologia Experimentalis et Applicata 142: 236 - 246

Pittman, HA (1927). Spotted wilt of tomatoes. Prelimary note concerning the transmission of the "spotted wilt" of tomatoes by an insect vector (Thrips tabaci Lind.). Aust J Counc Sci Ind Res 1: 74-77

Ramkat RC, Wangai AW, Rapando PN & Lelgut DK (2008). Cropping system influences Tomato spotted wilt virus disease development, thrips population and yield of tomato (Lycoperscion escullentum). Journal of Applied Biology, 153, 373-380

Rapando P, Wangai AW, Tabu I & Ramkat R (2009). Variety, mulch and stage of inoculation effects on incidence of tomato spotted wilt virus disease in cucumber (Cucumis sativus L.) Archives of Phytopathology and Plant Protection 42: 579 - 586

Riley DG, Joseph SV, Srinivasan R & Diffe S (2011). Thrips vectors of tospoviruses. Journal of Integrated Pest Management 1(2): DOI:10.1603/IPM10020

Samuel G, Bald JG, Pittman HA (1930). Investigations on "spotted wilt" of tomatoes. Australia Commonw Counc Sci Ind Res Bull No. 44

Schreiter G, Butt TM, Beckett A, Vestergaard S, Moritz G (1994). Invasion and development of Verticillium lecanii in the western flower thrips Frankliniella occidentalis. Mycol. Res. 98(9): 1025-1034

Sin S-H, McNulty B, Kennedy GG, Moyer, JW (2005). Viral genetic determinants for thrips transmission of Tomato spotted wilt virus. PNAS 102, 5168-5173

Ullman DE (1996). Thrips and Tospoviruses: Advances and future directions. Acta Horticulturae 431: 310-323

Ullman DE, Cho JJ, Mau RFL, Hunter WB, Westcot DM, Custer DM (1992): Thrips-Tomato Spotted Wilt Virus interactions: Morphological, behavioral and cellular components influencing thrips transmission. Advances in Disease Vector Research 9: 195-240

Ullman DE, Meideros R, Campbell LR, Whitfield AE, Sherwood JL, German TL (2002). Thrips as vectors of tospoviruses. Advances in Botanical Research 36:113-140

Ullman DE, Whitfield AE, German TL (2005). Thrips and tospoviruses come of age: Mapping determinants of insect transmission. PNAS 102: 4931-4932

Van de Wetering F, Goldbach R, Peters D (1996). Tomato spotted wilt tospovirus ingestion by first instar larvae of Frankliniella occidentalis is a prerequisite for transmission. Phytopathology 86: 900-905

Wangi AW, Mandal B, Pappu HR & Kilonzo S (2001). Outbreak of tomatoes spotted wilt virus in tomato in Kenya. Plant Diseases, 85: 1123

Whitfield AE, Ullmann DE, German TL (2005). Tospovirus-Thrips interactions. Anny Rev Phytopathol 43: 459-489

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Web links
Tomato spotted wilt virus
Mound´s Thysanoptera pages
Thysanoptera Checklist
ICIPE Thrips survey sites
UNI Halle & Thrips sites
Thrips of California

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