@SuppressFBWarnings on a field only suppresses findbugs warnings reported for that field declaration, not every warning associated with that field.
For example, this suppresses the “Field only ever set to null” warning:
@SuppressFBWarnings("UWF_NULL_FIELD")
String s = null;
I think the best you can do is isolate the code with the warning into the smallest method you can, then suppress the warning on the whole method.
Note: @SuppressWarnings was marked deprecated in favor of @SuppressFBWarnings