Commercial-Scale Thermotherapy for Combating Citrus Greening (Huanglongbing)

Abstract. Citrus greening disease (Huanglongbing, HLB) is a destructive bacterial infection of citrus which clogs vascular tissues and results in the death of the tree. Lacking any clear biological cure, citrus growers have begun to explore the use of thermotherapy as a method of impeding the spread and diminishing the effects of citrus greening in commercial groves. Thermotherapy, also called heat treatment, is the use of heat to eliminate disease from plants and produce and has been used at smaller scales for pathogen elimination since the early 20th century. The goal of the thermotherapy process for treating HLB is to heat a citrus tree to a temperature at which the citrus greening bacteria is killed, but the tree itself is left unharmed. However, the practical and technological challenges of using thermotherapy on mature citrus trees are unique and unperfected, especially considering that to-date only a handful of commercial-scale citrus thermotherapy machines exist, all of which are located in Florida. Using practical experiences from researchers and citrus growers in Florida, current thermotherapy methods and technologies are detailed, and initial lessons learned from application of thermotherapy to over 5000 trees in Central Florida are discussed.