Can new wife's income be garnished or taxes intercepted for child support arrears from ex-wife.

The answer to your question is no. You are obligated to support your children, not your soon to be new wife.  Her income and assets cannot be used in any way to pay support under your divorce decree. There can be an inquiry as to whether she works and what her income is, but at the same time, under Wisconsin law, her income cannot be considered or used for what are your support obligations.