Lethal Palm Diseases Common in the United States

Abstract

Palms (Arecaceae) are affected by a variety of pathogens, most of which are fungi. We detail pathogens, host ranges, disease description, diagnosis and epidemiology as well as management for the significant, usually fatal, diseases affecting palms grown in the continental United States and Hawaii. These include fusarium wilt (Fusarium oxysporum f.sp. canariensis) of canary island date palm (Phoenix canariensis), diamond scale (Phaeochoropsis neowashingtoniae), ganoderma butt rot (Ganoderma zonatum), lethal yellowing (Candidatus Phytoplasma palmae subgroup 16SrIV-A), and diseases caused by Nalanthamala (Gliocladium), Phytophthora, and Thielaviopsis. We have omitted the leaf spot and minor blight diseases that often affect palms but pose no long-term consequence to their health and survival. Visual symptoms of lethal palm diseases are often similar, necessitating the isolation or detection of the pathogen with cultural, microscopic, or molecular methods. Management of palm diseases is varied, often requiring in-depth knowledge of the biology of the pathogen and its' infection process. Quarantine, eradication, sanitation, and proper species selection and culture are necessary practices to limit the spread of new and existing diseases of palms in landscapes and nurseries.