News on the palm’s disease and now a Florida oak problem!

6 June 2014 Idea of the day “It’s what you learn after you know it all that counts.” John Wooden

Well the results came in from the DNA lab in Ft. Lauderdale. The Canary Island Date palm came back negative for Texas Phoenix Palm Decline. We still don’t know what it is because it’s already been taken down and we have no material to take a second sample. But it was too risky to leave up. The techs said it might also be weevils which are so large they would be easily visible inside the trunk, but we didn’t know to look at the time it was removed. The doctor at the lab was surprised it didn’t come back positive as all the signs were there. There are cases of false negatives, so she recommended a second test but unfortunately the palm was gone. The expensive large palms in the community will have to be closely monitored for symptoms of decline. As I mentioned in a previous post, they can be saved if caught early enough.

The Phoenix dactylifera Medjool palm, shown here,Johnson distressed date
turned out to be POSITIVE for Texas Phoenix Palm Decline (TPPD) way up near Dade City. It’s fatal at this late stage. It’s a large $8000 loss to the owner and it’s a sad scene because another can’t be planted to match the one across from it that gracefully framed his gated entrance. He has about 10 others on property and all are now at risk. We are planning to immediately remove the dead one and then inoculate the others with the Oxytetracyline anti-biotic. The problem is it has to be administered every 4 months for the life of the palms to keep them protected now that the bacterium is in the area. And its not just his date palms that are threatened. The state tree of Florida, the sabal palmetto (colloquially called “cabbage palm”) is also vulnerable to this disease. There are vague reports that even his 40 ft. high Washingtonian palms may be susceptible. This disease has the potential to wipe out a lot of the grand Florida palms that give the state its tropical appearance. Fortunately this owner can afford the anti-biotic applications, has ranch hands whom we can train to do the injections and it should work out. Not every homeowner is so fortunate.

A few months ago I was called down to the downtown Tampa Convention Center where a Medjool date palm had been confirmed for TPPD. Then just yesterday I was driving down the freeway just north of downtown and I saw four or five more stately date palms that looked dead from the same disease. Not good. If you live in the area and know a homeowner with one of these species of palms, let them know. The first thing to look for are the lower fronds starting to excessively brown. The orange flower stalks can be the next thing to turn brown. If the central spearhead leaf at the top goes brown and falls over or the orange flowers go brown, the palm has had it. So the palms have to be tightly monitored. It can all happen in two or three weeks.

Also this week I was called out to a newer development on the southeast side of Tampa. They had something strange happening with their oak trees that two previous arborists thought was from the trees planted too deep.

I arrived and came in the entrance drive and noticed the approximately ten year old laurel oaks lined on both sides of the street with touches of brown leaves at the tips. Hmmm, I thought, most likely is “black twig borer”, a relatively harmless pest that likes Maples and Laurel Oaks in Florida and bores into the tips of these trees but doesn’t go further and the tree gets through it. But that usually happened in late summer and here it was early June. That was the first sign something wasn’t right.

But then I was shocked – an oak further down the line was COMPLETELY DEAD with all its leaves brown. Another one was 75% gone. I had never seen this with black twig borers.

Trees don’t die from just one stress factor. It’s typically three to five of these “stressors” that add up to lower their immune system. The accumulated stress then makes the tree susceptible to something that comes along and becomes the final blow to kill it. The final stressor gets blamed but healthy trees, just like healthy humans, don’t get sick.

I pulled out my spade and clippers. I quickly found four stressors.
1) All of these trees had been planted far too deep. This is one of the worst stresses on a tree as it suffocates the roots. They don’t get the oxygen they need to digest the carbohydrates created by photosynthesis at the leaves. So the tree’s energy gradually depresses. Flare roots should display and be exposed to air, so plant your trees high with this in mind.

2) Even after ten years in the ground I was digging and finding synthetic root ball bags and their straps not deteriorated at all like natural burlap bags do, but biting into the flare roots and choking off water and nutrients that flow through them to get to the upper canopy. A second stressor for sure.

3) The landscapers had “volcanic mulching” going on, with excess soil and mulch pushed up against the trunk of the trees. A horrible practice (even if they think it looks pretty) because it further suffocates the roots, creates a too moist root environment which can lead to root rot, creates nests for insects and rodents (and I was finding ant colonies galore!) which can gnaw at the trunks and creates an environment for root mats to develop which start growing over the support flare roots and girdling and choking them. A third stressor had also been giving these trees a hard time.

4) The species itself should never have been planted here. Laurel oaks are one of the weakest species of oaks in Florida, only live about 50 years in the urban environment and grow fast and brittle creating lots of hazardous dead wood as they get past 30 years old. A stressor of a sort because they don’t heal from break wounds as fast and generally aren’t as strong as a species like a live oak, sycamore, elm, hickory, bald cypress, magnolia, etc. or smaller ornamental that could have been planted here like crape myrtles.

5) I noticed later that in the community itself an additional stressor was being set up by planting these oaks (which get very large when mature) in tiny spaces between the sidewalks and the streets. Not only are their roots going to be constricted by the concrete on both sides but the roots will uplift and damage these surfaces with expense and headaches for the residents for years to come. Builders think they can do it all themselves on the cheap, but when planting trees they need to consult professionals for species that are appropriate to a particular space. They should have hired an arborist or landscape architect. We see this ALL the time in developments. Twenty years later they are calling us because their sidewalks and curbs are cracking!

As I finished noticing all this, I walked back to get a birds-eye view of the problem and was in for ANOTHER shock. My God, some of the laurel oaks (the weakest ones with the most stressors) in the adjacent native woods on both sides of the entrance drive were ALSO showing signs of their leaves turning brown in large volume, not just the tips! This was definitely no minor problem.

I called the owner of the tree company I work with and found out he had found two similarly, mysteriously dead live oaks over near Clearwater a few weeks before. The plot was thickening, not in a pleasant way.

The other arborists hadn’t noticed this. But the trees in the woods obviously didn’t have the stressors of planted too deep, volcano mulching, plastic root bag straps acting like tourniquets around the flare roots and yet they were manifesting the same symptoms. They may have contracted the fungus from underground root contamination or insects. I found the symptoms throughout the community. I wrote up my preliminary report to the property manager and she approved lab testing of samples.

Central Florida hasn’t ever had a serious oak disease problem. Wholesalers could have brought new tree stock in from a farm as far away as Louisiana. Insects can travel far across the Gulf states. Even firewood with a particular fungus can be transported across state lines and then insects transfer them to healthy trees. Texas has had serious Oak Wilt which wipes out entire communities of oaks. Laurel oaks and live oaks are both very susceptible to Oak Wilt. Central Florida’s predominant tree canopy cover are oaks. This could be a real problem.

I snipped off root and leaf and branch samples, put them in collection bags and put them in refrigeration for the night. Early the next morning I shipped them off to the University of Florida plant pathology lab for analysis. Browning from the tips inwards only described Oak Wilt to me but there are a variety of things that attack oaks. It will be very interesting to see what the lab finds out. You may need to know this information to protect your oaks. And of course condo and homeowners associations are very concerned about the expense of such sweeping diseases, not to mention homeowners.

Of course this is an example of why it is always recommended to vary the species you plant in cities so that a single disease problem doesn’t wipe out most of the trees in a neighborhood, city or county like Dutch Elm disease has in northern states. Unfortunately most builder developers have over planted live and laurel oaks in the last thirty years because they “do so well”. Their “easy decision” may end up being a very bad one – it already is causing cracking sidewalks, driveways and streets. But this could be a lot more pervasive.

Come back in a few days or weeks to find out what we’re running into here in Central Florida.

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