This is the easiest and perhaps the most cost effective method. Thrips hide in weeds and those weeds also carry viruses, so it is important to keep weeds out of the greenhouse, and also to controlling the weeds surrounding the greenhouse. Use 200-400 mesh screens on the out side of vents and doors, even if the screens are a little bigger it will still deter most from entering. Some of the most efficient ways are to only buy in healthy stock plants that have been thoroughly inspected for thrips and grow seeds when ever possible. Thrips are difficult to manage because they feed deeply in the flowers and buds where they are sheltered from chemicals.
Thrips also develop tolerances to chemicals very easily.
Some factors to take into account when applying insecticides, is that you will want small spray particles, around 100 microns, so smokes and aerosol fogs work well. It is also important that you rotate the chemicals being used every three weeks. Another hint to good application is the addition of sugar to the pesticide to enhance thrips activity. The other thing you need to do is to try and time your spraying so that you avoid spraying the pupal thrips since this is when they are least affected by chemical controls. On the next page is a list of 10 multiple choice questions for you to answer.