Evaluation of monitoring methods for thrips and the effect of trap colour and semiochemicals on sticky trap capture of thrips (Thysanoptera) and beneficial insects (Syrphidae, Hemerobiidae) in deciduous fruit trees in Western Australia

Abstract

Western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), plague thrips (Thrips imaginis Bagnall), and onion thrips (Thrips tabaci Lindeman) are pests of deciduous fruit trees in Australia. Yellow sticky traps and tapping buds and flowers for thrips are currently recommended for monitoring, but it is not known whether one method is more efficient than the other, or if selectivity could be optimised by trap colour, or addition of semiochemicals Thriplineams® or Lurem-TR lures to traps. The number and species of thrips caught by trapping and tapping of flowers and leaves, on different trap colours (black, blue, green, red, yellow, white), including a control (clear) and thrips semiochemicals, were evaluated in a series of trials in commercial deciduous fruit orchards in the Perth Hills, Western Australia. There was poor correlation between thrips caught on traps and tapping samples (R2 = 0.00–0.05), with tapping less likely to trigger the action threshold and yielding less than 1% of the number of thrips caught on sticky traps. More thrips (F. occidentalis, T. imaginis and T. tabaci) were caught on blue, yellow and white bases, than on clear, red, green or black bases. On commercially available sticky traps, seven times more F. occidentalis were caught on ‘Seabright blue’ traps than yellow. The addition of semiochemicals increased capture of F. occidentalis by three times on baited compared to unbaited traps, on yellow and ‘Seabright’ blue traps. Thriplineams® attracted F. occidentalis, but had no effect on the capture of T. imaginis or T. tabaci, whilst Lurem-TR attracted more F. occidentalis and also increased the capture of T. imaginis. More beneficial insects including brown lacewings (Micromus tasmaniae (Walker)) and hoverflies (Melangyna viridiceps (Macquart)) were caught on blue trap bases (1.6 times more) than other trap base colours. No beneficial insects were present during the Thriplineams® experiment, whilst Lurem-TR increased trap capture of brown lacewings by 1.3 times. A monitoring system incorporating blue sticky traps in conjunction with Thriplineams® would be more selective at detecting and monitoring F. occidentalis in deciduous fruit in Australia.