Because of potential contamination of mulches from pesticides, mulch use is being called into question and testing may be required for mulches applied to organic orchards.  This is a recent ruling.  As always, anything applied to a certified organic operation should be cleared with the certifier first.

http://www.prnewswire.com/news-releases/beyond-pesticides-federal-court-finds-usda-process-for-allowing-pesticide-contaminated-compost-improper-and-stops-use-300288112.html