A new disease of palm trees has just been positively verified in Baton Rouge. Until now, lethal yellowing in the United States had been reported only in Florida, mostly the southern third of the state.
Lethal yellowing is a systemic disease caused by a phytoplasma and transmitted by the planthopper Haplaxius crudus. The disease has infected 37 different palm species so far worldwide. In Baton Rouge, it was detected in silver date palms and Chinese windmill palms.
While the disease has not been reported in the greater New Orleans area, diligence on the part of horticulturists and palm tree owners can help reduce the impact of the disease in our area.
No single symptom is diagnostic of lethal yellowing. But some symptoms may include blackened emerging flower spikelets, premature fruit drop and yellowing of the foliage beginning with the oldest fronds and progressing upward. Apical meristem, or spear leaf death, usually follows quickly. Diseased trees usually die within five months.
The symptoms are very similar to date palm lethal decline (aka Texas Phoenix palm decline) also caused by a phytoplasma.
The planthopper is a strong flyer and can be carried by the wind, so trying to manage the disease by controlling the planthopper is not very efficient. Quarterly trunk injections with oxytetracycline HCl are the treatment recommendation from Florida. The injections don't eliminate the pathogen, but they do help protect trees from infection or suppress pathogen populations in asymptomatic infected trees. Trees that test positive for infection should be removed as quickly as possible or they will serve as a source of infection for other, as yet, uninfected trees.
The only way to definitively diagnose the disease is with molecular diagnostic tests. These can be performed by the LSU AgCenter’s Plant Diagnostic Center in Baton Rouge. More information and forms can be found at lsuagcenter.com/plantdiagnostics.
Q: My lawn is starting to look a little pale. Is now a good time to fertilize? – Casey
A: This time of the year lawns are slowing down even in our subtropical climate, and you want to let them continue that natural process of getting ready for the cooler, lower light conditions of winter. Spring and summer are the ideal times to fertilize your lawn, no matter what type of sod you have. Application of a potassium (K) rich fertilizer such as potash is not a bad idea for the fall because the potassium will help the roots during the cooler weather. It's also a good idea to take a soil sample early in the year to help you prepare for the next active growth of spring. You can find more information on the LSU AgCenter website, especially the publication “Louisiana Lawns Best Management Practices.”