If the additional damage was significant enough the heads will continue to look bad for a while though the product worked. I suggest you spray the foliage with an insecticidal soap product very early or very late in the day. This will help wash off the sooty material and will also do a fair job of controlling any remaining thrips or whiteflies. Check the hedge for whiteflies periodically and if need be treated again making sure to get good coverage throughout the hedge. In the meantime continue to water and fertilize the hedge regularly in order to encourage good regrowth and vigor.
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