Evaluation of monitoring methods for western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), during the blossom period of 'Granny Smith' apples


  • S. J. Bradley Department of Entomology Washington State University Prosser, WA 99350
  • D. F. Mayer Department of Entomology Washington State University Prosser, WA 99350


Commercial sticky board traps (150 x 100 mm) of three different colors (blue, white or yellow) were treated with one of two chemical attractants (p-anisaldehyde and ethyl nicotinate) and with the solvent ethanol. Blue and white traps caught four and three times more thrips respectively than yellow traps. Attractants improved catches by only about 20% and were not considered economical. If traps are used, a plain blue trap is recommended. Trapping, beating tray and flower cluster flicking monitoring methods were compared. Trapping gave a time-averaged indication of thrips numbers, but numbers are probably affected by location of the trap and flowering stage of the apple. The beating tray method was the most versatile. It could be used regardless of flower condition and produced instant results. The currently recommended flower cluster flicking method produced few thrips and is affected by condition and age of the flowers, as well as time of day. We conclude that it is an ineffective method. Monitoring thrips numbers after blossom using a beating tray may give more practical economic thresholds for treatment.

Key words: thrips; apples; Frankliniella occidentalis