Also known as: Awka Disease, Cape St. Paul Wilt, Kaincope Disease, Kribi Disease, and Pudricion Del Cogollo
Lethal Yellowing* (LY) is a plant disease that infects and kills coconut palms as well as many other ornamental palm species.
Researchers have found that the causal agent of LY is a phytoplasma. Phytoplasmas are very small, not much larger than viruses, and lacking a true cell wall (unlike most bacteria), variable shaped, that posess a tri-laminar unit membrane, ribosomes, DNA, but no organized nucleus. It's commonly referred to as a mycoplasma-like organism or MLO**. MLO's represent a unique genetic cohesive group of plant pathogens.
Mode of Spread
Research has shown that LY is spread by planthopper type insects, one of which is called Myndus crudus.
The insect acquires the MLO that causes LY when feeding on diseased palms. As the insect moves to healthy palms to feed, the disease is spread.
*First used to denote a specific disease of coconut palms in Jamaica and was subsequently applied to diseases of identical symptomology.
How do I know if I have LY?
Coconut palms suffer from nutritional deficiencies due to the high alkalinity of the Keys soil. Many symptoms can be confused as LY.
Other causes of yellowing and defoliating symptoms of coconut palms:
- Fungal bud rot
- Nutrient deficiencies - Mn, Mg, Fe
- Insects and nematodes
- Lightning damage (see photo below)
All coconut palms are susceptible to LY. Healthy palms have the best chance of survival. Using slow release palm special fertilizer is recommended for optimal palm health.
See the Palm Nutrition Guide for more information on fertilizing your palms.
More palm information:
Stage 1 Symptoms
- Premature dropping of coconuts or "shelling."
- The fallen nuts will have a brown or black area under the calyx on the stem end.
Pictures courtesy of N. Harrison
Stage 2 Symptoms
- Blackening of new inflorescence tips (flower stalks). Almost all the male flowers will be dead and no fruit will set.
Stage 3 Symptoms
- From which the disease gets it's name "Lethal Yellowing."
- The fronds turn yellow, usually beginning with the older ones near the bottom and advancing upwards towards the crown.
The use of host resistant palms represents the most stable, long-range control measure for LY. Only plant native South Florida/Keys palms, or LY resistant palm species.
Treatment of LY with Antibiotics:
- Only recommended as part of a long term plan in which transition is made from susceptible to resistant palms.
- Use if palm is a rarity or of considerable worth to landscaping.
- Coconuts from treated palms trees are not recommended for human consumption.
- Treatment is costly and an ongoing process.
Environmental Horticulture Agent
- Entomology and Nematology Department
- Environmental Horticulture Department
- Extension Soil Testing Laboratory
- Florida-Friendly Landscaping
- Florida Yards & Neighbors
- Gardening in a Minute
- Horticultural Sciences Department
- IPM Florida
- Living Green
- Pesticide Information Office
- Plant Pathology Department
- Soil and Water Science Department