Tomato spotted wilt tospovirus (TSWV), a thrips-borne plant virus, occurs globally in economically damaging levels in agricultural, ornamental, and greenhouse crops. In North Carolina, TSWV is vectored primarily by the tobacco thrips, Frankliniella fusca (Hinds), and the Western flower thrips, F. occidentalis Pergande, both of which can acquire and subsequently transmit TSWV only by feeding on infected foliage as young larvae. Females oviposit in suitable plant tissues; therefore, only those plant species susceptible to systemic infection and with the ability to support reproduction by vector species have the potential to be important sources of virus inoculum. We conducted systematic plant surveys to determine the incidence of TSWV and the relative abundance of thrips vector species on summer annual and perennial plants commonly associated with susceptible crops in North Carolina. Frankliniella occidentalis was the most abundant vector and comprised >75% of vector species collected from 18 wild plant species during the summer and fall of 2002. The number of F. occidentalis and F. fusca larvae collected from plant samples, whose presence indicates a plant?s suitability for reproduction, varied significantly among the species sampled. The plant species yielding the largest collections of immature F. occidentalis were tall morningglory (Ipomoea purpurea), carpetweed (Mollugo verticillata), sicklepod (Cassia obtusifolia), and Palmer?s pigweed (Amaranthus palmeri). Plant species most suitable for F. fusca reproduction included Florida pusley (Richardia scabra), M. verticillata, and ivyleaf morningglory (I. hederacea). During surveys of wild plant species in or adjacent to highly TSWV-infected crop fields, TSWV was documented at 16 of 17 locations (94.1%) and in 14 of 30 weed species (46.7%). Estimated rates of infection were highest in I purpurea (6.8%) and I. hederacea (1.9%). Mollugo verticillata returned an unusually high proportion of marginally TSWV-positive samples and conservative estimates of infection rate were 0.5%. However, the actual importance of this species as a TSWV reservoir may be much greater, as liberal estimates (assuming marginal samples were indeed TSWV-infected) indicate an infection rate of 5.4%. These findings document that only a limited number of summer annual or perennial weed species are potentially important TSWV reservoirs or support high levels of vector reproduction in North Carolina. The temporal characteristics of vector abundance and dispersal were documented in the summer and fall of 2002 using aerial sticky traps surrounding 9 agricultural fields. Of vector species captured, 83.3% were F. occidentalis, 11.9% were F. fusca, and the remaining 4.8% were Thrips tabaci Lindeman. The timing of F. occidentalis dispersal, as indicated by mean cumulative proportions of F. occidentalis caught on traps, varied significantly among locations. Patterns of fall dispersal were unrelated to senescence of summer annual weeds, cultivation practices, or the first freeze date. Temporal patterns of TSWV movement were monitored with sentinel tomato plants (Lycopersicon esculentum var. ?mountain fresh?) at the same locations where aerial sticky traps occurred. TSWV-infected sentinel plants were recovered, sporadically and unpredictably, over a 3-month span in the fall of 2002. TSWV movement was not related to thrips dispersal, cultivation date, or summer weed maturation.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-02272004-101929 |
| Date | 18 March 2004 |
| Creators | Kahn, Noah D. |
| Contributors | George G. Kennedy |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-02272004-101929/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
Page generated in 0.0054 seconds