Population ecology of Thrips palmi (Thysanoptera:Thripidae) in orchid farms in Thailand

Abstract

The population dynamics and in-farm distribution of Thrips palmi Karny were evaluated in two orchid farms, one in the Bangkok metropolitan area and the other in Ratchaburi Province, Thailand. Yellow sticky traps were hung above the orchid canopy (three traps/220 m2), and the trapped adults were counted weekly from November 2009 to October 2010 at the first location and from January to December of 2012 at the second location. T. palmi nymphs and adults were both counted weekly on 300 orchid panicles in an area of 2,200 m2 at both locations. We found that the T. palmi population dynamics at the first location was represented by a W-shaped curve, with the distribution clumped throughout the year, whereas the curve was J-shaped at the second location, with the distribution mostly clumped. Qualitative surveys of thrips species were conducted on ten different orchid genera in ten locations and on 20 different Dendrobium hybrids in 20 locations. Five random sampling plots (1 × 4 m2) were examined on each farm. The results indicated that only T. palmi was found on every farm. Moreover, quantitative comparison among five orchid types revealed that Dendrobium flowers with darker color are more attractive to T. palmi. However, this phenomenon does not coincide with Oncidium sp. and Mokara sp. because of their unfavorable morphology for thrips behavior.