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FLOWER THRIPS (THYSANOPTERA: THRIPIDAE) COLLECTED FROM VEGETABLES, ORNAMENTALS
AND ASSOCIATED WEEDS IN SOUTH FLORIDA ABSTRACT
Galen Frantz & H. Charles Mellinger Following the outbreak of Western Flower Thrips, Frankliniella occidentalis (Pergande), in north Florida in 1985, collections of thrips were made from various crops and weeds in south Florida in an effort to detect this potentially damaging pest. Between 1986 and 1990 them collections contained primarily F. bispinosa (Morgan) among 25 species collected. Collections made in May 1990 indicated Western Flower Thrips were displacing F. bispinosa on the east coast of Florida and had moved into the Belle Glade and west coast areas as well. Although the 2 main vector of Tomato Spotted Wilt Virus in Florida were detected, this disease was only found in a situation which suggests that Tobacco Thrips, Frankliniella fusca (Hinds), may be the more important vector. Thrips are a diverse group of insects, inhabiting a variety of plants from cultivated crops to woodlands, and from flowers to fungi. Most are plant feeders but a few are predaceous. Thrips cause economic damage, either by feeding and egg laying activity, or as vectors of Tomato Spotted Wilt Virus (TSWV), which threatens numerous crops worldwide (5,7). Thrips damage has been recorded in Florida for nearly 100 years. Quaintance (4) noted the incidence of 2 species, Thrips tritici, Osborn (Fitch) on strawberries and fruit crops, and Thrips tabaci Lindeman on onions and cole crops. In 1912 Watson (8) reported heavy damage to tomato blossoms by Frankliniella (= Euthrips) tritici. Ten years later Watson (9) presented details of Frankliniella bispinosa Morgan, which he equated to Quaintance's T. tritici based on an illustration in Quaintance's report (4). Watson described damage caused by F. bispinosa on citrus, strawberries, and tomatoes, among other crops. The tomato damage consisted of a blackening, withering and eventual shedding of blossoms when infested by high numbers of thrips. In May 1985, an unusual blemish was observed on tomato fruits grown in Gadsden County, Florida. This consisted of a small puncture, surrounded by a slightly raised white area, 3-7 mm in diameter. Most blemishes disappeared as the fruit turned red, but economic losses were reported. Similar damage was observed in Collier County, Florida in the winter and spring of 1985-86 (Glades Crop Care, Inc. unpublished data). At the time different theories of the cause were offered, e.g., disease, environmental stress or insect activity. However, in 1989, Funderburk and Salguero (2) determined the blemishes resulted from oviposition by the Western Flower Thrips (WFT), Frankliniella occidentalis (Pergande). A commonly occurring blemish in Collier County, consists of a simple puncture, without the surrounding white tissue. This damage appears after high numbers of thrips have been in the field. Another type of thrips damage was observed in May 1990, when pepper fruits were found infested with high numbers of thrips. The thrips congregated in large numbers where fruits or leaves were in contact with each other. The feeding resulted in patches of scar tissue 1-3 cm in diameter. In May 1986, the authors discovered TSWV infecting tomatoes in the Gadsden County area and this was published by the Florida Division of Plant Industry (DPI) (3). The level of TSWV infection was between 0.1 and 1 % for most fields and at least three fields had over 10% infected plants at harvest. At that time Glades Crop Care, Inc. (GCC) determined that to apprise vegetable growers of the risk of TSWV incidence, a survey of thrips in and around the fields serviced should be undertaken. Denmark (1) indicated WFT had been collected in Florida since 1982, citing ornamental plants as commonly infested hosts. He also reported the collection of WFT from field crops in 1985 from the panhandle area. Subsequent collections of WFT by the DPI continue to show this association with ornamentals; and, most collections occur in the Orlando, Tampa and Florida East Coast growing areas, and at Miami by way of California (H. Denmark, FL Div. of Plant Industry, personal communication). The immediate objective of this study was to survey the species composition of thrips populations in the vegetable growing areas of south and southwest Florida populations, in order to determine when WFT or other TSWV vectors would be present. The overriding goal was to prepare vegetable and ornamental growers and their pest management programs for the potential of TSWV in south Florida. The east coast production area was first represented in the survey in the spring of 1990, when collections were submitted by GCC personnel in Dade County and by Kenneth Schuler, Palm Beach County Extension Agent. |