Temporal and spatial distribution of thrips in Israel
Ben-Yakir D, Jasrotia P, Chen M
Entomology Department, Institute of Plant Protection, ARO, The Volcani Center, P.O. Box 6, Bet-Dagan, Israel 50250.
Correspondence: benyak@volcani.agri.gov.il
We used pole traps to determine the annual and daily variations in the migration activity of Thrips tabaci and Frankliniella occidentalis. The pole traps were 3m high and were placed near walk-in tunnels and in open fields at 4 different geographical locations in Israel. Thrips populations were peaked between April and June depending on the environmental conditions at each location. Twice as many thrips were caught on the pole at the eastern entrance of the tunnels than at the western entrance. At almost all sits, the highest numbers of thrips were caught on the eastern side of the poles (40每50%) and the lowest numbers were caught on the western side (10每20%). Annually, about 75% of the thrips were caught before noon time, and about 50% were caught below the height of 70 cm. In preliminary trials in which the eastern entrance of the tunnel was covered, it reduced thrips entry significantly with only a slight effect on ventilation efficacy. This information can be used to reduce the risk of thrips entry into greenhouses. Rabbit immunoglobulin G (R-IgG) was used successfully as an external mark for thrips. Females of both Thrips tabaci and Frankliniella occidentalis were marked with R-IgG solution (1 mg/ml water with 1% Tween 20) by the contact exposure method. Determining the retention of the mark was done by running the rinsing solutions of individual thrips in an enzyme每linked immunosorbant assay (ELISA). The sandwich ELISA method was used with an additional biotin-avidin step that increased the assay＊s sensitivity by 3每5 folds. When marked thrips were kept in the laboratory on bean pods they all scored positive 6 days after marking (DAM). All marked thrips scored positive 2 DAM when kept in the laboratory on detached marigold flowers. When marked and unmarked thrips were placed together on these flowers some mark had transferred and 10每20% of the unmarked thrips turned positive. Under field conditions, a gradual decrease in the mean optical density levels of the marked thrips was observed over time. On sticky pole traps, 100%, 85% and 15% of the marked T. tabaci scored positive by the 3rd, 6th and 9th DAM, respectively. Under the same conditions 100% and 15% of the marked F. occidentalis scored positive by the 6th and 9th DAM, respectively. Similar rates of positive scores were recorded for marked T. tabaci kept on chive plants for 6 DAM. The retention of the R-IgG mark decreased significantly under conditions of wetness and high humidity. The suitability of this marking method for dispersal studies of these important pests need to be evaluated now.
