Plant parsley chives or garlic at the base of rose bushes to repel them. They move very quickly. Thrips like a dry environment keep your rose beds moist. Lace wings and lady bugs are predators of thrips. Spray with insecticidal soap or Neem Oil from the time blooms are in tight bud, through full bloom.
Thrips hide within the petals.
To see them, fold back the petals, exposing the flower base. The bottom leaves on the plant appear to be covered with fine dots of yellow on the top and undersides of leaf surfaces. Leaves turn yellow and fall off. Microscopic in size, these insects may be visible to the unaided eye as reddish specks. They can spread very quickly, and favor the hottest days in midsummer.