Survey, Seasonal Abundance of Thrips Species and First Record of Two Thrips Species Associated With Soybean and Weed Plants in Egypt

Abstract

Several thrips species are known to feed on soybean (Glycine max Merr.) and can cause yield reduction. Beside, the other important reason for thrips survey is to determine its role as vectors of Tospovirus in soybean. There is little information available about thrips species present on soybean crop, and their abundance in Egypt. Field survey took place at the farm of Agricultural Experiment Station, Faculty of Agriculture, Cairo University, Giza Governorate, Egypt (season 2014) to survey the different thrips species. Soybean cv. Giza 111 was sown in late May. The experimental area received all the usual agricultural practices except for any pest control measures. Thrips species associated with soybean were collected and differentiated to species. A total of 16 different thrips species was surveyed. These included 14 phytophagous and 2 predator thrips species. The most abundant species was Thrips tabaci with an average No. 226.2individual/plant, it had two major peaks on soybean, the first peak was at late June (21.9 individual/ plant), while the second one was occurred on mid-August (38 individual/plant). Frankliniella occidentalis occupied the second rank (107.02 individual/plant, Neohydatothrips variabilis came third in that order (57.5 individual/plant) followed by, Caliothrips phaseoli, F. tritici and F. Schultzei ( 42.1 & 43.2, 56.5individual/plant respectively). N. variabilis, Caliothrips phaseoli and F. schultzei werereached their highest numbers (13.2, 19.4 & 16.3 individual/plant) by the end of the season, respectively.Generally speaking, both soybean thrips, N. variabilis and bean thrips, Caliothrips phaseoli, were recorded for the first time in the present study. Characterization and identification of both two species are presented. There were 27 weed plant species collected from soybean field. Both of T. tabaci and F. occidentalis were the most common species of soybeanand associated weeds.The highest average No. of thrips species was recorded on Ammi majus L. (70.7 individual/plant) followed by Medicago intertexta L.,Convolvulus arvensis L., Melilotus indicus L., and Malva parviflora L., which harboured (52.3, 48.8, 44.3 & 44.5 individual/plant, respectively), while the lowest average no. (3.3 individual/plant) was occurred on Urtica urens L. Seasonal abundance of the thrips species associated with weeds, proved that both T. tabaci and F. occidentalis were the most dominant species (36.7 & 17.4 individual/ weed plant, respectively). In conclusion, weeds can serve as reservoir alternative hosts for plant viruses and thrips vectors, therefore should be considered when endeavoring to manage and control plant viruses of cultivated soybean plants.