Lethal Palm Yellowing Disease
Lethal yellows (LY) is a deadly disease of coconut palms and 34 other palm species. The causal agent is a phytoplasma, which is vectored by the homopteran cixiid (insect) Myndus crudus V.D. in the Caribbean, and another cixiid, M. adiopodoumeensis in West Africa. The disease is pandemic in the Caribbean, West Central America, and Central Africa, and has caused major losses in these areas. From the 1930s to the mid 1960s, 75% of the coconut palms succumbed to LY in Key West, Florida. It is also found in Texas on date palms. Symptoms include premature fruit drop, blackening of inflorescences, yellowing of leaves, death of spear leaf, and toppling of crown, leaving a bare trunk. Infected trees die within three to seven months after symptoms appear. Although tetracycline has some effect, it does not control the disease under field conditions. The use of resistant varieties is recommended. Insecticides have had mixed results. The most highly susceptible coconut variety is the Jamaica Tall (=Atlantic Tall). Tolerant coconut varieties are the Malayan dwarfs, while some resistant palms areRoystonea regia (royal palm), and Sabal palmetto (cabbage palmetto). Susceptible palms include, Caryota mitis (fishtail palm),Caryota rumphiana (giant fishtail palm), Livistona chinensis(Chinese fan palm), Livistona rotundifolia (footstool palm), Phoenix canariensis (Canary island date palm), Phoenix dactylifera (date palm), Pritchardia affinis (loulu palm), Pritchardia pacifica (fan palm), Pritchardia thurstonii (Thurston palm), Veitchia arecina, andVeitchia merrilii. Pandanas utilis Bory (Pandanaceae) or screwpine is also a host of LY.
Most of the coconut trees in Hawaii are believed to be susceptible to LY. The decimation of coconut trees in Hawaii would significantly impact its “Paradise in the Pacific” image. This could have a devastating impact on tourism, Hawaii’s primary economic industry. The disease would also impact palm nurseries.