I believe I made a mistake when I wrote that Anna was still living during the 1930 census with her son Fred, etc. This seems to be the wrong Anna with a son Fred, as this Fred and mother Anna was also in the 1920 census in Grover, whereas Julius and Anna were in the 1920 census in Enterprise.
So, Julius' Anna most likely died in 1925 as stated at findagrave.com, but I did not find an obit for her in the Oshkosh paper.
1930 United States Federal Census
Home in 1930: Grover, Marinette, Wisconsin
Household Members: Name Age
Fred Kushman 40
Martha Kushman 32
Adeline Kushman 10
Glen Kushman 8
George Kushman 6
Marion Kushman 4 3/12
Anna Kushman 67, mother, widow