Onion thrips (thrips tabaci) are the most important insect pest of onion in Australia. It is a tiny, slender, free-moving insect that is often found in large numbers in onion. Both adults and nymphs feed by piercing and rasping the leaf surface and drinking the liquid. When feeding areas are large, the plant’s ability to photosynthesise and maintain water balance is greatly reduced, resulting in yield loss or reduced bulb size. Onion thrips may also enter harvested bulbs and breed there, thus reducing marketability of bulbs.