scholarly journals The Role of Weed Hosts and Tobacco Thrips, Frankliniella fusca, in the Epidemiology of Tomato spotted wilt virus

Plant Disease ◽  
2002 ◽  
Vol 86 (6) ◽  
pp. 573-582 ◽  
Author(s):  
R. L. Groves ◽  
J. F. Walgenbach ◽  
J. W. Moyer ◽  
G. G. Kennedy

Wild plant species were systematically sampled to characterize reproduction of thrips, the vector of Tomato spotted wilt virus (TSWV), and natural sources TSWV infection. Thrips populations were monitored on 28 common perennial, biennial, and annual plant species over two noncrop seasons at six field locations across North Carolina. Sonchus asper, Stellaria media, and Taraxacum officianale consistently supported the largest populations of immature TSWV vector species. The tobacco thrips, Frankliniella fusca, was the most abundant TSWV vector species collected, comprising over 95% of vector species in each survey season. Perennial plant species (i.e., Plantago rugelii and Taraxacum officianale) were often only locally abundant, and many annual species (Cerastium vulgatum, Sonchus asper, and Stellaria media) were more widely distributed. Perennial species, including P. rugelii and Rumex crispus, remained TSWV infected for 2 years in a small-plot field test. Where these perennial species are locally abundant, they may serve as important and long-lasting TSWV inoculum sources. In random surveys across 12 locations in North Carolina, TSWV infection was documented by double antibody sandwich enzyme-linked immunosorbent assay in 35 of 72 (49%) common perennial (N = 10), biennial (N = 4), and annual (N = 21) plant species across 18 plant families. Estimated rates of TSWV infection were highest in Cerastium vulgatum (4.2%), Lactuca scariola (1.3%), Molluga verticillata (4.3%), Plantago rugelii (3.4%), Ranunculus sardous (3.6%), Sonchus asper (5.1%), Stellaria media (1.4%), and Taraxacum officianale (5.8%). Nine plant species were determined to be new host recordings for TSWV infection, including Cardamine hirsuta, Eupatorium capillifolium, Geranium carolinianum, Gnaphalium purpureum, Linaria canadense, Molluga verticillata, Pyrrhopappus carolinianus, Raphanus raphanistrum, and Triodanis perfoliata. Our findings document the relative potential of a number of common annual, biennial, and perennial plant species to act as important reproductive sites for F. fusca and as acquisition sources of TSWV for spread to susceptible crops.

2001 ◽  
Vol 91 (9) ◽  
pp. 891-899 ◽  
Author(s):  
R. L. Groves ◽  
J. F. Walgenbach ◽  
J. W. Moyer ◽  
G. G. Kennedy

Overwintering of tobacco thrips, Frankliniella fusca, was investigated on common winter annual host plants infected with Tomato spotted wilt virus (TSWV). Populations of tobacco thrips produced on TSWV-infected plants did not differ from those produced on healthy plants, whereas populations varied greatly among host plant species. The mean per plant populations of F. fusca averaged 401, 162, and 10 thrips per plant on Stellaria media, Scleranthus annuus, and Sonchus asper, respectively, during peak abundance in May. Adult F. fusca collected from plant hosts were predominately brachypterous throughout the winter and early spring, but macropterous forms predominated in late spring. Weed hosts varied in their ability to serve as overwintering sources of TSWV inoculum. Following the initial infection by TSWV in October 1997, 75% of Scleranthus annuus and Stellaria media retained infection over the winter and spring season, whereas only 17% of Sonchus asper plants remained infected throughout the same interval. Mortality of TSWV-infected Sonchus asper plants exceeded 25%, but mortality of infected Stellaria media and Scleranthus annuus did not exceed 8%. TSWV transmission by thrips produced on infected plants was greatest on Stellaria media (18%), intermediate on Scleranthus annuus (6%), and lowest on Sonchus asper (2%). Very few viruliferous F. fusca were recovered from soil samples collected below infected wild host plants. Vegetative growth stages of Stellaria media, Sonchus asper, and Ranunculus sardous were more susceptible to F. fusca transmission of TSWV than flowering growth stages, whereas both growth stages of Scleranthus annuus were equally susceptible. In a field study to monitor the spatial and temporal patterns of virus movement from a central source of TSWV-infected Stellaria media to adjacent plots of R. sardous, the incidence of infection in R. sardous plots increased from <1% in March to >42% in June 1999. Infection levels in the Stellaria media inoculum source remained high throughout the experiment, averaging nearly 80% until June 1999 when all Stellaria media plants had senesced. Dispersal of TSWV from the inoculum source extended to the limits of the experimental plot (>37 m). Significant directional patterns of TSWV spread to the R. sardous plots were detected in April and May but not in June. R. sardous infections were detected as early as March and April, suggesting that overwintering inoculum levels in an area can increase rapidly during the spring in susceptible weed hosts prior to planting of susceptible crops. This increase in the abundance of TSWV inoculum sources occurs at a time when vector populations are increasing rapidly. The spread of TSWV among weeds in the spring serves to bridge the period when overwintered inoculum sources decline and susceptible crops are planted.


2000 ◽  
Vol 27 (2) ◽  
pp. 49-52 ◽  
Author(s):  
L. E. Garcia ◽  
G. G. Kennedy ◽  
R. L. Brandenburg

Abstract A comparison of the survival and reproductive success of Frankliniella fusca (Hinds) (Thysanoptera: Thripidae) on tomato spotted wilt virus (Bunyviridae: Tospovirus) (TSWV) infected and uninfected peanut plants was conducted under greenhouse conditions in North Carolina. Three cultivars—NC 9, NC-V11, and NC 12C—adapted to North Carolina production practices were evaluated. A total of 180 individually caged plants, in three replicates, were infested with 20 female F. fusca each. Adult and larval thrips were collected after 30 d on the plants. Final counts were square root transformed and a mixed model analysis of variance conducted. Effects of cultivar and the virus-by-cultivar interaction were not statistically significant. TSWV-infected plants had significantly fewer adult and larval F. fusca than did uninfected plants for adults (P = 0.04) and for larvae (P = 0.01). This study reports on an alternative method of assessing TSWV resistance among peanut cultivars and the trend appears to support the conclusions of a previous field study, which found NC 9 more susceptible to TSWV than either NC-V11 or NC 12C.


Plant Disease ◽  
1998 ◽  
Vol 82 (11) ◽  
pp. 1282-1282 ◽  
Author(s):  
H. R. Pappu ◽  
J. W. Todd ◽  
A. K. Culbreath ◽  
M. D. Bandla ◽  
J. L. Sherwood

In Georgia, tomato spotted wilt tospovirus (TSWV) causes significant losses in peanut, tobacco, tomato, and pepper. Transmission of TSWV in Georgia primarily is by tobacco thrips (TT), Frankliniella fusca (Hinds), and western flower thrips, F. occidentalis (Pergande), with TT being the predominant vector species in peanut (2). TSWV must be acquired at the larval stage for the adult to transmit the virus. Detection of NSs (a non-structural TSWV protein present only following virus replication) in thrips by enzyme-linked immunosorbent assay (ELISA) is a reliable indicator that the virus had multiplied in the vector and thus the vector is competent to transmit TSWV. While this has been accomplished with F. occidentalis (1), information is lacking for F. fusca, the predominant vector in Georgia and other states in the Southeast. Thus, the nature of the TSWV-TT association was investigated and the proportion of transmitters in a field population determined in 1,436 individual adult TT collected from sticky cards positioned in selected peanut fields in south Georgia. Additionally, 650 larvae collected from volunteer peanut plants were reared to adults in the laboratory and the resulting 295 adult TT were individually evaluated by ELISA. Of those collected from the sticky cards, NSs was detected in 8% of the adult insects, indicating that the virus had multiplied in TT. NSs was not detected in control TT that had no access to the virus. Of the adult TT that emerged from larvae collected from volunteer peanuts, 6.1% were positive for NSs. Our study provides the first immunological evidence that TSWV multiplies in TT. References: (1) M. D. Bandla et al. Phytopathology 84:1427, 1994. (2) J. R. Chamberlin et al. J. Econ. Entomol. 86:40, 1993.


2003 ◽  
Vol 30 (1) ◽  
pp. 38-42
Author(s):  
L. E. Garcia ◽  
R. L. Brandenburg ◽  
G. G. Kennedy ◽  
J. E. Bailey ◽  
J. R. Bradley

Abstract Overwintering of Frankliniella fusca (Hinds), tobacco thrips, in North Carolina and their subsequent spring movement into peanut fields were evaluated using two winter sampling techniques and three spring sampling techniques at the Peanut Belt Res. Sta., Lewiston, NC. In the spring of 1992 and 1993, for 14 d following peanut planting, the aerial movement of tobacco thrips was monitored using cylindrical sticky traps, trap plants, and exclusion cages. Frankliniellafusca were trapped significantly more often at 0.2 m and 0.9 m than at 1.8 m and during the afternoons. Thrips catch was significantly influenced by prevailing wind direction. No thrips were caught on sticky traps on days when maximum temperatures did not exceed 18.7 C. Frankliniella fusca began to colonize emerging peanut plants as they cracked the soil surface on days when there were temperatures above 18.7 C and times when there was no precipitation. Aerial F. fusca movement was monitored with sticky traps for three consecutive winters during 1993–96. Tobacco thrips were collected on sticky traps throughout the winter; however, counts were lower in months and years with lower temperatures. Tobacco thrips, caged throughout the winter with peanut plants infected with tomato spotted wilt virus (TSWV), were analyzed for the presence of a nonstructural protein (NSs) encoded for by the small RNA of TSWV and infectivity by ELISA. A total of eight tobacco thrips were collected, of which one tested positive.


Plant Disease ◽  
1998 ◽  
Vol 82 (8) ◽  
pp. 959-959 ◽  
Author(s):  
R. L. Groves ◽  
G. G. Kennedy ◽  
J. F. Walgenbach ◽  
J. W. Moyer

Tomato spotted wilt virus (TSWV) is an economically important virus of many crops throughout the world. Cotton, Gossypium hirsutum L., has previously been demonstrated to be susceptible to TSWV (1). During the fall of 1996, cotton was assayed as a potential host of TSWV, as it is an important early season host of thrips vectors of TSWV. Four commercial cotton varieties (DP 20, DP 52, DP 5409, and HS 46) were screened for susceptibility to four isolates of TSWV: two from tobacco, one from pineapple, and one from dahlia. Greenhouse-grown plants in the first true leaf stage were inoculated mechanically. Mean percent infection ranged from 20 to 33% (x = 27%) across all cotton varieties screened against all virus isolates 21 days post-inoculation. TSWV was recovered through mechanical inoculation from double antibody sandwich-enzyme-linked immunosorbent assay (DAS ELISA) positive cotton leaves in 83% of indicator plants, Emilia sonchifolia (L.) DC. ex Wight. Individual cotton plants testing TSWV ELISA positive were held for an additional 28 days with 4% of these again testing virus positive. The four cotton varieties were tested in the cotyledon, one-leaf, and four-leaf stages for susceptibility to tobacco thrips, Frankliniella fusca Hinds, transmission of one TSWV isolate from tobacco. First instar thrips were obtained from an avirulent colony. Mean percent infection among all varieties assayed was 10, 63, and 5%, respectively, for the three developmental stages. Cotton appears to be most susceptible in the one-leaf developmental stage with potential to serve as a source for TSWV spread to other crops. Reference: (1) G. L. Schuster and R. S. Haliwell. Plant Dis. 78:100, 1994.


Plant Disease ◽  
2000 ◽  
Vol 84 (4) ◽  
pp. 459-464 ◽  
Author(s):  
L. E. Garcia ◽  
R. L. Brandenburg ◽  
J. E. Bailey

Virginia-type peanut (Arachis hypogaea) cultivars were monitored for incidence of Tomato spotted wilt virus (TSWV) and abundance of Frankliniella fusca, the tobacco thrips, in North Carolina during 1995 and 1996. A preliminary evaluation of 225 peanut genotypes for TSWV-resistant or -tolerant genotypes was conducted in 1995. The incidence of TSWV in cultivar NC-9 was twice that of cultivar NC-V11. In 1996, field trials designed to evaluate TSWV susceptibility were conducted with three widely grown commercial peanut cultivars in North Carolina. They were NC-9, NC-V11, and NC-12C, a newly released cultivar. A randomized complete block design was utilized at three locations. Disease incidence was evaluated weekly from 2 weeks postplanting until 2 weeks prior to harvest. Mechanical inoculation of the three cultivars resulted in no difference in relative leaf virus titer as determined from optical density readings following DAS-ELISA for 4 successive weeks beginning at 13 days postinoculation. NC-9 ranked highest in incidence of disease (7%), followed by NC-12C (6%) and NC-V11 (5%). Thrips counts were greatest on NC-V11, followed by NC-9 and NC-12C. Disease incidence overall was 5.96%, but ranged from 3.08 to 11.15% among the three sites. Yield was affected by the temporal occurrence of symptoms beginning at the fifth week postplanting. Greatest yield losses occurred in those plants with the earliest visible foliar symptoms.


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