There have been numerous reports of dying or dead arborvitae in Iowa in 2012 and 2013.  The staff at the ISU Plant Diagnostic Clinic have not see any signs of insect or disease problems on arborvitae specimens submitted to the clinic in 2012 and 2013.  Weather was likely the main factor in the decline and death of the arborvitae.  The weather conditions over the last 3 to 4 years have been difficult for many evergreens (including arborvitae).  The main problems have been the excessive rainfall in 2009 and 2010 and the extreme heat and drought of 2012.  As a result, some arborvitae and other evergreens have died over the last 8 to 12 months.   

Arborvitae perform best in moist, well-drained, fertile soils. They can successfully be grown in full sun to partial shade.  Poorly drained soils can be problematic (especially in wet years).