Significant damage on vegetable crops by tospoviruses had occurred sporadically in Argentina in the past but since 1994, severe outbreaks have been recorded every year. The crops that have been most affected, tomato, lettuce, and pepper, were surveyed in the provinces of Mendoza and Buenos Aires in 1994–95 and 1995–96. A few weeds and miscellaneous crops were also collected. A total of 543 samples showing symptoms typical for tospoviruses were analysed by double‐antibody sandwich‐enzyme‐linked immunosorbent assay with polyclonal antibodies to groundnut ringspot tospovirus (GRSV), impatiens necrotic spot tospovirus (INSV) and tomato spotted wilt tospovirus (TSWV). The 339 samples collected in 1995–96 were also assayed for tomato chlorotic spot tospovirus (TCSV). In addition, the incidence of tospoviruses in tomato crops was assessed in 41 farms representing 310 ha and 10 cultivars. GRSV was identified in 222 samples (40.8%), TSWV in 194 samples (32.7%), TCSV in 50 samples (14.7%), INSV was not detected and 77 samples did not react with the antisera used. TSWV was found to prevail in Buenos Aires and GRSV in Mendoza. Mixed infections were not found in this survey. In tomato crops the mean incidence of tospoviruses was 33%. These results show that the disease formerly assigned to TSWV, is caused by at least three tospoviruses.

The objectives of this work were to estimate the capability of local populations of thrips as vectors of groundnut ringspot virus (GRSV) and tomato spotted wilt virus (TSWV), and to determine the species composition of vectors in tomato crops. Transmission assays were performed. Incidence of tospoviruses was estimated in commercial crops. Random samples of flowers were taken from tomato for identification of thrips. Of the five species of thrips tested, Frankliniella gemina (first record), F. occidentalis and F. schultzei transmitted GRSV and TSWV. F. schultzei was a significantly more efficient vector of GRSV than F. occidentalis under controlled assay conditions. The thrips were identified on flowers from six surveyed tomato crops. F. occidentalis was the most frequently identified species (43.0%), followed by F. schultzei (35.6%) and Thrips tabaci (10.1%). The incidence of tospoviruses was low (1.1-2.8%) in crops planted during August-September and greater (9.5-61.1%) in crops planted in December. GRSV was prevalent (85%) over TSWV (11%).www.blackwell-synergy.com

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In August 1996, a severe viral disease occurred in squash produced in the subtropical Province of Salta, Argentina. Plants of Cucurbita pepo L. (zucchini) and Cucurbita maxima L. ‘Any’ were affected. Approximately 50% of the plants showed prominent yellow mosaic, necrosis, and foliar distortion. Most of the fruits on infected plants were small, with scattered glossy yellow knobs over a green background, and some showed additional fruit malformation. A potyvirus was isolated from infected plants by mechanical transmission. Filamentous particles were associated with symptomatic inoculated squash and cucumber plants in leaf-dip preparations with an electron microscope (Elmisckop I, Siemens, Germany). The particles were flexuous rods ≈755 nm long. The host range of the isolated virus was mostly limited to the cucurbits (systemic infection) but also included Gomphrena globosa (local and systemic symptoms) and Chenopodium quinoa and Chenopodium amaranticolor, which showed only local chlorotic lesions. Twenty species in the Compositae, Leguminosae, and Solanaceae were not infected (2). In agar double-diffusion tests with sodium dodecyl sulfate (SDS)-degraded virus particles, no reactions were observed with Papaya ringspot virus, Watermelon mosaic virus (WMV), and WMV-Mo antisera, but a strong precipitin line was obtained with the antiserum prepared by Purcifull (1) for isolate 1119 of Zucchini yellow mosaic virus (ZYMV). Isolate 1119 and our isolate appeared serologically indistinguishable in SDS immunodiffusion tests. Both gave fused precipitin bands without spur formation. The results (field symptoms, transmissibility, host range, particle morphology, and serology) lead to the conclusion that ZYMV is present in Argentina. Since 1996, outbreaks have occurred every year in Salta, devastating squash crops. In 1998, ZYMV also was found in the provinces of Mendoza and San Juan, infecting zucchini squash and melons (Cucumis melo L.). A survey of crops indicates that disease incidence and severity were lower than in Salta. References: (1) D. E. Purcifull et al. Plant Dis. 68:230, 1984. (2) H. L. Wang. Plant Dis. 76:530, 1992.

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