Renate and welcome! I live in south Florida and thrips can be a spring time problem here. Martin Motes is a local expert who sends out a very helpful monthly newsletter (this mainly is for growing outside in South Florida) but here is his advice from the April newsletter:
"The warmth of April, alas, stimulates the growth of bugs as well as plants. Both thrips and mites thrive in the dry heat of April. Liquid dishwashing soap (at 2 oz per gal) will control both but be mindful that soap should not be applied to plants that are suffering from drought stress. Be sure that your plants are well hydrated before you apply soap. Water them extra hard the day before. To be effective soap must be used profusely. The plants should be washed in the solution to the point of wetting every nook and cranny of both the plant and its container. Only such thorough treatment can reach the reclusive thrips and be sure to touch all of the ever prolific mites. A second treatment at 7-10 days is necessary to control mites and a miticide such as Kelthane might be advised. Orthene which is the insecticide of choice for thrips (because of its residual action) is compatible with many miticides. Check with your county agent if in doubt." Hope that helps!