When re-landscaping or fixing irrigation, it is very important to protect the root system of existing trees on your property. Trenching for new irrigation or electrical can damage the root system on established trees, damage that may not be noticed for many seasons after the construction has been completed. Severing large diameter roots can cut off water and nutrients to a large area of the tree, potentially causing branch and limb dieback.
Collapsing palm trunks? Foul smelling ooze expelling from the trunk?There has long been debate about what causes palm trunks to collapse over or snap off towards the top of the trunk. In the last few months, I have been fortunate to be able to witness a few date palms with these symptoms and quickly pull samples and send to the lab for pathogen testing. The samples taken end up being positive for Thielaviopsis paradoxa, or Thielaviopsis Trunk Rot of Palm.
As I monitored select palms that were under stress (from other environmental factors), a few common symptoms of this disease were observed: holes in trunks and they were easily swayed when climbed. Some palms also were bleeding from the trunk that produced such a foul smell that would even gag a maggot. While some palms seemed reasonably healthy, a few did show signs of stress, mainly older fronds dying, new fronds starting to brown at the tips and look a bit pale. Since this problem is often discovered after the tree has collapsed, the easiest thing to do is perform ‘sounding’ on the trunk. Using a mallet, knock on the trunk and listen for hallow or different sounding ‘thud’. You might want to ask your tree expert to perform sounding while trimming the palm each summer. If you do discover a hallow space in the trunk, find out how extensive the void is in the trunk. If it is a small void, call me and we can discuss treatment options.
If it extends through much of the trunk perimeter, you will have to perform a risk assessment and determine if the palm should be removed. Most often date palms are planted at entries where there is heavy traffic. If a tree has a potential to fall on a target, the risk may outweigh the costs to remove and replace with the new palm. As I get more calls about date palm issues, it makes we wonder if this is epidemic in our area. Since all situations need to be assessed individually, it is not safe to say Thielaviopsis is killing all our date palms; however it might be an explanation when all other issues such as overwatering and poor drainage have been ruled out.