Palm tree problems

Over the last couple of months we, on Statia, have seen some of our coconut trees developing the terrible disease known as Lethal Yellowing. It affects palm trees, mostly Coconut Palms and Date palms but up to 30 different varieties are known to be susceptible. Although treatments are available in the form of injections of the anti-biotic Oxytetracycline there is no known cure for the disease at the moment.

Here are some of the things to be on the look out for in your palms. Dropping of all nuts/fruits both mature and immature, blackening of flower stalks, excessive drooping and yellowing leaves at first towards the base of the crown and then extending into the top and eventually death of the terminal bud and crown of the tree. All leaves on palms will at some point show some yellowing, sometimes it’s a mineral deficiency or as the leaf is dying off it will lose some of it’s normal green colour, this is normal yellowing and not associated with the LY disease. The time to be concerned is when you see yellowing leaves in conjunction with any other symptoms or if the yellow leaf is up in the crown of the tree. I have posted some pictures to show these symptoms in more detail at the end of the post. Once a tree starts to show signs of the disease it will usually die 3-6 months later unless treated.

The disease is believed to be spread by the planthopper insect. The insect lives in grass, eats palm sap and infects the tree as it feeds. It is thought that the importation of grass seeds from Florida to turf golf courses, larger hotels and gardens on some of the more developed tourist islands is how the disease began to take hold in the Caribbean.

On Statia there appears to be several trees dying from LY at the moment, we have had 2 at the STENAPA office and littered along the bay road and around Golden Rock are more trees either showing definite symptoms or that have already succumbed and are just long, leafless, trunks.  Here are a few things you can do to limit the risk to your trees.

• Don’t plant grass around the base of your palms, if you can limit the exposure of the planthoppers to your trees you can reduce the risk. Plant them in a separate flower bed and use other ground covering plants such as Purple Heart, Beach Morning Glory (Sea Bean) or Lady in a boat.
• Although no cure is available, the life of the tree can be extended by administering injections of Oxytetracycline on a quarterly basis (available to buy on the internet.) This has to be done carefully and according to instructions as trees can be more susceptible to fungal infections around the site of the injections.
• Remove any dead or infected trees as soon as possible from your yard. Be careful when sawing or cutting the tree and collect all the debris and burn it.
• Ensure that you disinfect any tools you use on infected trees thoroughly before using them on any other trees. You can do this by dipping them in a solution of Lysol or something similar before drying them and oiling (WD40 is fine) as you normally would.

By far the best way to reduce your risk (and the only 100% effective way) is to invest in cultivars and palms that are resistant to the disease in the first place. Maylaisian Dwarf varieties were considered to be resistant and were the replacement tree of choice for many years. Now many of the varieties have been cross bred with other taller varieties and so their natural resistance has been too watered down. Fijian Dwarf varieties are now being tried in some areas and these seem to be showing good resistance for the time being. Ask your nursery or supplier about LY resistant varieties and they will be able to advise you on your choices.

Here are some pictures I took along the bay road near the STENAPA office in the last couple of weeks.

Notice here that the palm in the fore-ground has the lower branches falling higher up the crown and browner than the one behind it, that one is still looking fairly healthy.

These palms have already died and the crowns have fallen. The palm in the background is still healthy. This is the stage at which the tree and all it's debris should be cleared as soon as possible as the disease will only spread and infect the other trees around it.

This is not the best shot ever (sorry) but you can see the leaves towards the top are yellowing, this is a sure sign of the disease. Sometimes lower leaves will have yellow spots but this does not mean they have lethal yellowing. The flower stems are also blackened, another sign of the disease, there are no visible nuts as they have all been shed and the lower branches are falling early. This tree has the early signs of the disease.

Hope all this helps with your trees. If you have any concerns you can always pop to the garden and we are always happy to help.

Good luck!

Much love from the garden on the golden rock…