Hiding the Target Audience field in New Forms

I am trying to hide the Target Audience field in the New Item form in a list using something similar to that found below;

SPField audienceField = newsItems.Fields[new Guid("61cbb965-1e04-4273-b658-eedaa662f48d")];
audienceField.ShowInNewForm = false;

This method works perfectly for any other field but not the Target Audience field. Has anyone experienced this issue or found a workaround?

Cheers

Josh