Rose Chafer Control (II)

Thanks very much for the information on rose chafer control. They seem to have done their damage and disappeared for this year. Should I spray with Scanmask now, in the fall or in the spring?

Spray now. They will have layed their eggs right after disappearing and you want the nematodes to get them either before they hatch or before they finish pupating. In the spring would probably work as well, but I shudder to think what their larvae will eat while invisible under the soil.