Population fluctuations of two Haplothrips species (Thysanoptera: Phlaeothripidae) in rice fields of Ilam province in various climate regions

The study was conducted to determine population fluctuation of two Haplothrips species in rice fields with two different climates. Samples were collected from different growth stages of rice in four fields located at Chardavol (cold climate) and Darreh-Shahr (Tropical climate) cities, in Ilam province (western Iran), during 2017-2018. Totally, eight thrips species belonging to six genera and three families were collected and identified. Amongst them, Haplothripsganglbaueri Schmutz and H. aculeatus (Fabricius) were the dominant species accounting for 73.16% and 17.83 (in Darreh-Shahr) and 61.19% and 27.25% (in Chardavol) in abundance. According to the results, both Haplothrips species in both cold and tropical regions were observed from the stem stage of rice. The highest density of adult for both Haplothrips species in Darreh-Shahr was related to dough stage of rice (0.8 and 0.33 thrips), but for both adult and larval stages was related to flowering stage of rice (0.9 and 1.40 for H. ganglbaueri, 0.33 and 0.6 for H. aculeatus). In addition, the highest density of adult for H. ganglbaueri in Chardavol was related to flowering stage of rice (0.73 thrips) and for larval stage and (adult+larva) was related to heading stage of rice (0.93 and 1.40 thrips). The above information for H. aculeatus for adult and (adult+larva) was related to dough stage (0.26 and 0.43 thrips) and for larval stages related to flowering stage of rice (0.23 thrips). The results of the T-test for two Haplothrips species between Darreh-shahr and Chardavol showed that there was no significant difference between the two regions. In general, population fluctuation for the immature stages of thrips in both regions showed the low density in beginning of rice growth and there was a decreasing in the flowering stage of rice. Adult thrips were also observed in the early stages of rice growth, so that the density of adults was low at the beginning of the season and then, after a gradual increase, the density of thrips decreased during the dough stage.