That's up to you. Some believe you can knock down a generation or two of the thrips by removing the flowers (where they live) and spraying. What they don't realize is, they come in on the wind, birds, animals, YOU... I live in the Central Coast of California. A century and a half ago when farmers moved into the coastal valley they complained of the endless sand, endless wind and endless spider mites (add thrips!). NOTHING has changed. You can spray and treat all you want and they STILL blow in on the wind and come in on any creature which wanders through your yard. The horrible Chilli Thrips do precisely the same thing. (as do the fungal spores which germinate on your roses and other plants, causing diseases) They all blow in on the breezes and literally fall out of the winds once they lessen to the point where they can no longer support the weight of the insects. So, if it makes you FEEL better to remove all of the flowers, as if it is actually accomplishing anything, remove them. If you don't want to, for whatever reason, I'd vote not to. Do I honestly think you're going to reduce the thrips or mites by removing them? Not really. If you have them, so does EVERYONE else around you. What makes anyone think they can eliminate them from their garden when the whole world around them is infested? You can possibly reduce their numbers a little, temporarily, but like any pest, when you remove one, it leaves a vacuum which is rapidly filled by another one.