(Thysanoptera: Thripidae) in Central and South Texas"
Tomato Spotted wilt virus (TSWV) is a cosmopolitan virus with a wide host range, and is vectored exclusively by thrips. Only nine of the more than 5000 described thrips species are proven vectors. Three of these, Frankliniella fusca (tobacco thrips), F. occidentalis (western flower thrips) and Thrips tabaci (onion thrips) occur in the southern United States.
In a typical scenario, TSWV will appear sporadically in an area, perhaps for years, then suddenly surge to epidemic proportions in agriculturally important host plants. Plant hosts and perhaps the thrips themselves act as reservoir sites for the virus. Wherever TSWV incidence has increased enough to cause economic losses, it has remained a chronic problem. This pattern has been repeated in India, Australia, Hawaii, and other parts of the world. Such a situation has now developed in the southern United States. TSWV incidence is on the rise in tomato, tobacco, pepper, peanut and in greenhouse and ornamental crops. Epidemics have occurred in peanut in Texas, Mississippi, Alabama, Georgia and Florida. Damage is severe. In south Texas, losses in peanut have been estimated in excess of $15 million over a two year period in a three county area. Epidemics in tomato have occurred in Texas, Louisiana, Arkansas and Florida. In some areas of California and Hawaii, tomato can no longer be grown due to TSWV infection, a situation which is also occurring in Louisiana.
In 1986, research was initiated by scientists from the Texas Agricultural Experiment Station on the TSWV epidemic occurring in peanut fields of south Texas. Extensive field data were collected by the entomology program through 1996 and document: thrips species composition in wild and cultivated host plants, thrips seasonal density and abundance in peanut fields, thrips movement, TSWV incidence and prevalence in peanut fields, effect of TSWV on individual plant growth parameters, number of TSWV contaminated thrips in the agroecosystem, number of thrips by species and developmental stage on infected and non-infected peanut that are contaminated by TSWV, and wild host species infected by TSWV. Similar data have also been collected for thrips populations in a similar non-epidemic agroecosystem.
Read more about this project in papers written by Dr. Mitchell and others:
"Flowering Weed Hosts Harboring Tobacco
Thrips, Frankliniella fusca (Hinds),
(Thysanoptera: Thripidae) in Central and South
Texas"
"Control of Thrips with Insecticides in North-Central and South Texas
Peanut Fields"
"Implementation of the IPM planting window for management of tomato
spotted wilt virus
and avoidance of peanut yellowing death"
**Note: This paper is in PDF format; in order to view it you must have Adobe Acrobat Reader 3.0. You can download a free copy of Adobe Acrobat Reader by clicking on the Get Adobe Acrobat Reader icon.
Other papers available for reprint order:
"Influence of Verbesina encelioides (Asterales: Asteraceae) on Thrips (Thysanoptera: Terebrantia) Populations and Tomato Spotted Wilt Virus Epidemics in South Texas Peanut Fields"
Forrest L. Mitchell and J. W. Smith, Jr.
Texas Agricultural Experiment Station, Route 2 Box 00, Stephenville,
TX 76401
ABSTRACT From October 1991 to November 1992, thrips (13,350), adults (12, 986) and larvae (364), were collected from the composite weed Verbesina encelioides. Of these, 5,229 adults were mounted on slides and identified to species. Four thrips-- Frankliniella minuta Moulton, F. tritici (Fitch), F. occidentalis (Pergande), and Microcephalothrips abdominalis (D. L. Crawford)--predominated in the routine sample counts. Supplemental samples of thrips were collected on 11 dates and 835 thrips were identified to species and assayed for tomato spotted wilt virus contamination by ELISA. Only 3 individual adult thrips (1 F. occidentalis, 1 F. fusca, and 1 F. tritici) were positive for tomato spotted wilt virus contamination by Double Antibody Sandwich (DAS) ELISA. Laboratory life tables demonstrated that both F. fusca and F. occidentalis developed from 1st instar to adult on foliage of V. encelioides. A paired sample test conducted in grower peanut fields infected with tomato spotted wilt virus rejected the hypothesis that peanut plants adjacent to V. encelioides were more likely to be infected with tomato spotted wilt virus than more distant plants. Thus, the hypotheses that V. encelioides was serving as a reservoir for primary spread of tomato spotted wilt virus in peanut and as foci for within field secondary spread of tomato spotted wilt virus by either recruiting competent thrips vectors into the fields or infecting the progeny of recruits with tomato spotted wilt virus was rejected.
"Survey by ELISA of Thrips (Thysanoptera: Thripidae) Vectored Tomato Spotted Wilt Virus Distribution in Foliage and Flowers of Field-Infected Peanut
Kenya K. Kresta, Forrest L. Mitchell, and J. W. Smith,
Jr.
Texas Agricultural Experiment Station, Route 2 Box 00, Stephenville,
TX 76401
ABSTRACT The foliage of individual field-infected peanut plants (Arachis hypogaea L.) was examined by enzyme-linked immunosorbent assay (ELISA) for the presence of tomato spotted wilt virus (TSWV). TSWV was detected commonly in terminals (folded quadrifoliates) and flowers, the vector's feeding and breeding niches. Reconstructions of the assayed plants demonstrated that the virus concentration varied from plant to plant and symptoms were significantly correlated to virus concentration in individual leaves and terminals. The virus was not distributed uniformly throughout individual plants but was concentrated in young, developing terminal tissue. The presence of symptoms was indicative of detectable virus 95% of the time.
"Insecticidal Management of Thrips in Texas Peanut Fields"
Forrest L. Mitchell, J. W. Smith, Jr., and H. B.
Highland
Texas Agricultural Experiment Station, Route 2 Box 00, Stephenville,
TX 76401
ABSTRACT Studies testing insecticidal compounds against thrips feeding in peanut were conducted at two sites in Texas--Stephenville (Erath County) in the northern region and Pearsall (Frio County) in the southern region. Products tested were aldicarb, acephate and disulfoton in at-plant, sidedress and split applications, and sulfur in split applications. Thrips populations were sampled weekly in terminals and flowers. A weekly census of both the number of terminals and flowers was used to establish absolute population densities of thrips. Control was obtained with all compounds tested except sulfur. However, control in northern Texas was reduced compared to studies conducted in previous years.