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Tomato Spotted Wilt Virus: Thrips Identification

Pre-season Risk Assessment of Thrips Vectors of Tomato Spotted Wilt Virus in Solanaceous Crops

Introduction:

Tomato spotted wilt (TSW) prediction in the southeastern U.S. has come a long way from the original weed surveys to try to estimate risk. Since the virus that causes this disease is vectored by two main species of thrips in Georgia: Frankliniella fusca and F. occidentalis, the models are linked to temperature models that predict thrips generations responsible for the main virus movement in the spring (see forecasting page at www.tswvramp.org). The old weed survey results are still posted here for informational purposes, but the forecasting page should be viewed for a more complete description of what is involved in TSW risk assessment and risk prediction.

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Old Survey Methods:

Monthly sampling to determine the presence of thrips populations surrounding and within two fields are conducted in Brooks, Colquitt, Decatur, and Tift counties, GA.

Method 1. Six sticky traps are placed along a transect outside the field and six parallel traps are run within the field. The outside traps serve as the center point of plots for weed collection. Each of the sticky traps consists of one yellow card and one blue card stapled to opposite sides of a 12" garden stake. The traps are left in the field for one week before returning them to the lab for counting.

Method 2. Sampling for TSW virus in weeds consists of harvesting host weeds in six plots adjacent to each production field. Florida pusley, purslane, morning glory, beggarweed, wild radish, and spiny sowthistle are targeted during the summer/fall season and chickweed, cudweed, sowthistle, Virginia pepperweed, swinecress, and Carolina geranium during the winter/spring season. Samples of each of the weeds present are collected and sent to the Virology Lab on the Tifton campus for ELISA to determine the level of TSW virus infection.

  • Photo: Samples being analyzedSamples from the weeds are collected in gallon ziplock bags and returned to the lab. The weeds are placed in Berlese funnels for three days which desiccate the weeds and force the thrips into alcohol vials. Thrips are counted and sorted into appropriate categories.
  • Crop leaf samples are taken during the growing season to estimate the percentage of TSW virus in the fields. One leaf sample is selected from the top 1/3 of 90 randomly chosen plants in the field. These samples are sent to the Virology Lab for analysis using ELISA.
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Former Project Results:

You will need Adobe Acrobat Reader to download or open the PDF files on this page.

 

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