Frankliniella occidentalis

The majority of thrips species are so small and cryptic that, except when present in very large numbers, many inspectors and commercial operators may fail to see them. Adults and larvae are able to hide in concealed places on plants such as beneath plant hairs, within tight buds, enclosed in developing leaves, or underneath the calyx of fruits. Eggs are laid concealed within plant tissues. Casual inspection may thus not reveal the presence of thrips, and even insecticide treatment may be ineffective because the chemical fails to contact the hidden thrips. Effective detection methods have yet to be deployed by most quarantine inspection systems, reliance usually being placed on inspection for feeding damage and simple beating to reveal thrips. However, adult and larval thrips can be extracted from plant material within two or three minutes if a sample is placed in a small Tullgren Funnel using turpentine as an irritant rather than light;the living thrips then run down into a glass tube at the bottom of the funnel where they are readily observed and counted.
Infestation levels in glasshouse crops are usually monitored by means of blue or yellow sticky traps. One shade of blue is particularly attractive to flying adult thrips and is widely used for monitoring the species (Brødsgaard, 1989a). Pheromone lures that attract males and females are now available to increase the sensitivity of monitoring at low levels of infestation or in easily damaged crops (Hamilton et al., 2005). Thrips can also be monitored by extracting thrips from flowers and recording their numbers or the percentage occupancy of flowers (Navas et al., 1994;Steiner and Goodwin, 2005). Western flower thrips adults are easily carried into glasshouses by wind, as well as on the clothes or in the hair of working personnel, thus making re-infestation from surrounding weeds a constant probability. Indeed, weed control around a crop, whether inside a glasshouse or on surrounding land, is the first measure to be adopted in any control strategy. Thrips are also easily carried on equipment and containers that have not been properly cleaned, and infestations in sterile laboratories with filtered air are usually due to thrips being carried in on the clothes and hair of workers. Nationally and internationally, F. occidentalis is readily transported to new areas on all types of planting material as well as on cut flowers, both commercial and domestic (Vierbergen, 1995).