Seasonal abundance of the western flower thripsFrankliniella occidentalis in the arava valley of Israel |
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Authors: | Raisa Chyzik Orna Ucko |
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Institution: | (1) Dept. of Entomology, ARO, The Volcani Center, 50250 Bet Dagan, Israel;(2) Plant Protection Dept., Extension Service, Ministry of Agriculture and Rural Development, 84100 Be’er Sheva, Israel |
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Abstract: | Flowers of 22 plant species grown in the Arava region of Israel were sampled at periodic intervals to study the seasonal abundance
ofFrankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). Samples were collected from the most common cut-flower and vegetable plant species
in this area during 1997 and from pepper in 1996–1998. Western flower thrips (WFT) was detected on 19 of the plant species
surveyed, and it reproduced on numerous plant species. WFT counts peaked in late February–April and in October–December. The
peak density of WFT during March in our survey corresponded to the peak flowering of cut-flower plants (during spring) and
sweet pepper (during autumn). Thrips population was less abundant during autumn than in spring and was very low during summer.
The possible reasons for fluctuations in thrips densities are abiotic factors (temperature and relative humidity), and availability
of flowering plants. The high temperature (>40°C) and low humidity (∼20%) in summer caused a drastic reduction in WFT populations,
although some flowering plant species were available in this season. WFT population remained low until October, when adults
appeared in large numbers on flowering pepper. We assume that the thrips had survived the hottest months by aestivation and
migrated to the plants when air temperature decreased. In most samples from the cut-flower fields, 84.8% were adult WFT; only
during the period from the end of January to March, did the proportion of immature stages in the thrips population increase
to 31.6%. Females always outnumbered males (71% females). In pepper fields during the first cropping month the thrips population
included 96% adults; from November onwards, the proportions of adults and immatures were almost equal; and females outnumbered
males. Organic pepper fields were not infested with thrips because of the presence of the predatory bugOrius albidipennis (Fieber).
Contribution from the Agricultural Research Organization. No. 534/00, 2000 series.
http://www.phytoparasitica.org posting July 16, 2002. |
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Keywords: | Frankliniella occidentalis western flower thrips seasonal abundance cutflower plants sweet pepper |
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