I have noticed a large drop in the number of BMSB at our house this fall. I did call the Clackamas Co Master Gardener line and the person I talked to had made the same observation at her house. Are there less BMSB or is the rainy weather keeping them hidden for now.
The following comments are not based on any sort of official comments, but reflect reports the Master Gardeners have received at the Washington County and Clackamas County offices. BMSB populations have been quite variable at the various sites where they congregate for the winter. And it seems that folks who live adjacent to wooded areas tend to have larger numbers from one year to the next than do people who live elsewhere.
In general, BMSB aggregate on the west- or south-facing exterior walls of structures on sunny warm days. They “disappear” on cooler days, but that’s only because they have migrated into the wall void. Rainy days will also encourage them to find shelter.
If you’re interested in obtaining detailed information, go to www.stopbmsb.org.