Epiblema otiosana - Hodges#3202 (Bidens Borer).
Size: approx. 5-10 mm. Photo: 04/07/15, 9 pm.

This moth has a striking white patch. It is Bidens Borer (Epiblema otiosana). The common name refers to the fact that the larvae bore into the stems of plants including ragweed. Go E. otiosana! The genus has 39 species. The small photos were taken on 09/10/11. 

bug guide (this photo):
moth photographers group: