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Tomato Spotted Wilt Virus: TSWV in Vegetable Crops: Tospoviruses

Tospoviruses In Solanaceae and Other Crops in The Coastal Plain of Georgia

Epidemiology

Weed Hosts
Natalia Martinez

Noncrop plant hosts will likely contribute to pathogen spread by serving as reservoirs for the virus and reproductive hosts for thrips that transmit the virus. Several studies worldwide report finding diverse plant hosts for tospoviruses. A survey of weeds around agricultural fields in Georgia from 2002-2004 revealed a large number of plant species naturally infected with TSWV. The type of plants that did not test positive for TSWV during the entire survey was very small and included species such as field pansy (Viola rafinesquii Greene), fumitory (Fumaria officinallis officinalis L.), hairy bittercress (Cardamine hirsute hirsuta L.), poorjoe (Diodia teres Walt), common pokeweed (Phylotacca americana L.), American burnweed (Erechtites hieraciifloia (L.) Raf. ex DC.), alyceclover (Alysicarpus vaginalis (L.) DC.), castorbean (Ricinus communis L.) and corn speedwell (Veronica arvensis L.).

The most common weeds found infected with TSWV are outlined in Tables 1 and 2, some of which we believe are new hosts recordings. Most weeds testing positive for TSWV were nonsymptomatic. Many of these weeds occur abundantly in the southeastern United States and are cause of major losses in agricultural crops such as peanut, cotton, tobacco and vegetables. The incidence of TSWV in weeds varied from year to year (Figs. 6, 7, 8) and also among seasons. The proportion of TSWV found in weeds seems to relate< with spotted wilt levels recorded in the crops affected those years. We believe the role of winter weeds is a key factor in understanding the epidemiology of TSWV, and perhaps virus levels detected prior to the cropping season might be an indicator of the spotted wilt to be expected. Other tospoviruses such as Impatiens necrotic spot virus (INSV) and Iris yellow spot virus (IYSV) have been found in weeds in Georgia and many overlapping hosts indicate that mixed infections are very likely to occur, increasing the complexity of the damage they can cause. The potential for survival and dispersal of tospoviruses is significant because the composition and amount of weed hosts found in Georgia year-round is very large.

Table 1. Survey of winter and spring weed species most commonly infected with Tomato spotted wilt virus (TSWV) at nine farms in Georgia from 2002 through 2004.
Plant species (common name)
Total TSWV incidence
Oenothera laciniata Hill (cutleaf evening primrose)
2.9% (42/1429)
Gnaphalium pensylvanicum Willd.
   (wandering cudweed)*
2.6% (32/1233)
G. purpureum L. (purple cudweed)
25.8% (23/89)
Lepidium virginicum L. (Virginia pepperweed)*
15.3% (23/150)
Eupatorium capillifollium (Lam.) Small (dogfennel)
11.2% (18/161)
Geranium carolinianum L. (Carolina geranium)
4.4% (17/383)
Verbena regida Spreng. (stiff verbena))*
6.3% (15/238)
Gnaphalium falcatum Lam. (narrowleaf cudweed)
26.4% (14/53)
Raphanus raphanistrum L. (wild radish)
3.5% (14/402)
Ambrosia artemisiifolia L. (common ragweed)
7.2% (12/167)
Solidago canadensis L. (Canada goldenrod)
4.9% (12/242)
Stellaria media (L.) Cyrillo (common chickweed)
17.9% (12/67)
Spergula arvensis L. (corn spurry)
3.7% (12/326)

*New TSWV host report
 


Table 2. Survey of summer and fall weed species most commonly infected with Tomato spotted wilt virus (TSWV) at nine farms in Georgia from 2002 through 2004.


Plant species (common name)
Total TSWV incidence
Jacquemontia tamnifolia (L.) (smallflower morningglory)
11.4% (129/1134)
Richardia scabra L. (Florida pusley)
5.7% (73/1282)
Portulaca pilosa L. (broadleaf pink purslane)
4.7% (47/1004)
Desmodium tortuosum (Sw.) DC. (Florida beggarweed)*
8.2% (40/490)
Amaranthus retroflexus L. (redroot pigweed)
14.8% (26/176)
Wahlenbergia marginata (Thumb.) A. DC.
   (southern rockbell)
14.2% (25/176)
Mollugo verticillata L. (carpetweed)
11.3% (24/213)
Ipomoea hederacea Jacq. var. integriuscula Gray
   (entireleaf morningglory)
8.4% (23/273)
Sida rhombifolia L. (arrowleaf sida)
5.5% (15/273)
Senna obtusifolia (L.) Irwin and Barneby (sicklepod)
6.2% (15/242)
Acanthospermum hispidum DC. (bristly starbur)
4.9% (10/203)
Croton glandulosus var. septentrionalis Muell (tropic croton)
6.8% (9/133)
Eclipta prostrata (L.) L. (eclipta)*
13.1% (8/61)

*New TSWV host report

 

Figure 6. Seasonal incidence of TSWV in weeds

Figure 6. Seasonal incidence of TSWV in weeds

Figure 7. Overall incidence of TSWV in weeds

Figure 7. Overall incidence of TSWV in weeds

Figure 8. Overall incidence of weeds

Figure 8. Overall incidence of weeds


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