If your site organic traffic is dropped off significantly and remains almost similar till a week, this post will let you identify and recover Google Panda effect
Google Panda : It is a domain based penalty, if you have created low quality content/thin content or duplicate content on your site earlier and it is still hosted under your domain name so not only those pages but whole of your domain will be penalized, it is not always the content is user created sometimes it may be created by CMS like Wordpress itself, removing these thin content can act as a quick fix for recovering from Google Panda penalty
Google Panda : It is a domain based penalty, if you have created low quality content/thin content or duplicate content on your site earlier and it is still hosted under your domain name so not only those pages but whole of your domain will be penalized, it is not always the content is user created sometimes it may be created by CMS like Wordpress itself, removing these thin content can act as a quick fix for recovering from Google Panda penalty