New Horizons in Insect Science Towards Sustainable Pest Management

160 N. Nagaraju et al.

important and major viral diseases can be identi-

fied through the visual symptoms (Fig. 1 ).

Plant viruses cause severe yield losses to the

cereal, vegetable, fruit, floral industries and sub-

stantially lessen the quality of crop products. Due

to virus infection, losses of over US$1.5 billion

are reported in rice in Southeast Asia (Hull 2002 ),

and estimates of losses have been calculated at

US$63 million in apple in the USA (Cembali

et al. 2003 ), and over US$20 million in potato

in the UK (Hull 2002 ). Tomato spotted wilt virus

(TSWV) alone is responsible for losses of over

US$1 billion in vegetable and ornamental crops.

TSWV is transmitted by thrips and has the larg-

est host range of any plant virus infecting more

than a thousand plant species from 84 families

(Parella et al. 2003 ).

Most plant viruses are absolutely dependent

on a vector for plant-to-plant spread. Although a

number of different types of organisms are vec-

tor for different plant viruses, phloem-feeding

hemipterans are the most common and transmit

Table 1 Vectors and plant viruses in relation to transmission. (Hogenhout et al. 2008 ; referred to the International Com-

mittee on Taxonomy of Viruses (ICTV), http://phene.cpmc.Columbia.edu/Ictv/index.htm)

Vector taxa Vector groups Virus groups

Icosahedral

particles RNA

genome

Rod-shaped

particles RNA

genome

DNA

genome

Enveloped

particles RNA

genome

Total %

Hemiptera Aphids 26 153 a 13 5 197 28

Whiteflies – 13 115 b – 128 18

Leaf hoppers 8 – 15 3 26 4

Plant hoppers 10 4 c – 4 18 3

Other Hemiptera – 8 5 – 13 2

Thysanoptera Thrips 2 – – 14 16 2

Coleoptera Beetles 50 1 – – 51 7

Acari Mites 10 9 – – 10 1

Nematoda Nematodes 45 3 – – 48 7

Mycota Fungi 8 16 – – 24 3

No identified

vectors

84 60 19 3 d 166 24

Total 233 268 167 30 697

% 33 39 24

a Includes 110 virus species of the genus Potyvirus, family Potyviridae

b Virus species of the genus Begomovirus, family Geminiviridae; these are all tenuiviruses that have multiple shapes

c Tenuiviruses that have multiple shapes

d These viruses probably have insect vectors

Table 2 Transmission characteristics and timing of plant viruses transmitted by hemipteran insects. (Hogenhout et al.
2008 ; referred to the International Committee on Taxonomy of Viruses (ICTV), http://phene.cpmc.Columbia.edu/Ictv/
index.htm)
Biological
characteristics

Nonpersistent

stylet borne

Semipersistent

foregut—borne

Persistent

circulative

Persistent

propagative

AAP and IAP Seconds, minutes Minutes, hours Hours, days Hours, days

Latent period None None Hours, days Days, weeks

Retention time in the

vector

Minutes, lost after

moulting

Hours, lost after moulting Days, weeks Lifespan of the vector

Presence in vector’s

hemolymph

No No Ye s Ye s

Multiplication in vector No No No Ye s

Transovarial

transmission

No No No Often

AAP acquisition access period, IAP inoculation access period