I decided to experiment last night by pinning up an old white bedsheet behind the trap. The results, though not conclusive suggest this was successful, my numbers going from mid-sixties to 114. I will continue to monitor this innovation.
Also new for the garden was a handsome pinkish noctuid. It reminded me a bit of a plain golden Y without the metallic elements. I knew I hadn't had it before, but a look at the book indicated a Rosy Rustic, not rare, but nice.