Characteristics of the migratory flight of the onion thrips (Thrips tabaci) and their relevance for pest management

The migratory flight of the onion thrips (OT) is expected to affect the invasion of new crops by this pest. We used 3.0 m high poles with blue sticky traps to study the daily and annual characteristics of OT migratory flight. About 70% of the thrips were caught at a height of less than 1.0 m above ground. About 90% of the thrips were caught when the wind speed was below 10 km/h. Most thrips were caught on the leeward side of the poles (50%) and the fewest on the windward side (15%). When we used similar traps that were mounted on wind vane, 75% of the thrips were caught on the leeward side. The risk of thrips entering greenhouses from the leeward side was twice as high as from the windward side. It appears that OT fly upwind during periods of light wind. In Israel, the highest numbers of OT were caught from April to July and from September to November. There were significant regional variations in OT migratory flight that were mainly related to the availability of host plants. Solutions of various proteins have been used for external marking in studies of thrips migration. This knowledge may be used to reduce the risk of OT invasion of new crops.