Of the many species of thrips commonly found in greenhouses, flower thrips (Frankliniella tritici), western flower thrips (Frankliniella occidentalis) and chilli thrips (Scirtothrips dorsalis) are most problematic. Chilli thrips is the fastest spreading thrips and is found throughout North America, but mainly in Florida and Texas. Adults of these three species are about 1 - 2 mm long, slender and just visible to the naked eye. Adult thrips are hard to notice flying in the greenhouse, but both nymphs and adults can often be detected in the open blossoms of your greenhouse crops.