While not necessarily connected with predatory publishing, citing retracted papers can decrease the reliability and credibility of your own papers. While some databases and journal publishers do a good job of flagging retracted articles, others do not. Below are some tools to help you identify retracted articles.
Screenshot of notice of retracted paper in Zotero.
Journal publishers will often include the retraction notice along with the paper. See the example from a retraction in IEEE.
This example from Computational Intelligence and Neuroscience shows another way that a retraction might be flagged by a publisher. In this example, a red box appears at the top of the page for the article with a warning of it's retracted status. See screenshot below.
