Cotton Root Rot

Cotton root rot is a serious soilborne fungal disease of cotton and numerous dicot plants in the south- western United States and northern Mexico. The disease is also known as Texas root rot, Phymatotrichopsis or Phymatotrichum root rot, and Ozonium root rot. Ozonium root rot was first described in cotton in Texas in the late 1800s and is now geographically confined in a region that stretches from eastern Texas and southern Oklahoma west through Arizona and south into Mexico (Lyda, 1978). In the US, cotton root rot is an economically important disease that causes approximately $ 100 million in annual losses to the cotton crop and severe economic losses to alfalfa, fruit and nut orchards and grapes. In Arizona, cotton root rot is found across the southern portion of the state. Highly prone areas include the flood plains and certain tributaries of the Gila, Santa Cruz, San Pedro, Colorado and Salt Rivers. The average loss of raw cotton fiber yield is estimated at 2.2 %, with losses of 8-13% in heavily infested fields. Cotton root rot is a major limitation to cotton production in Arizona and is often difficult to manage, even with conventional strategies and fungicide flutriafol (Topguard Terra).