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Bacterial colonies on coconut palm leaves


RoystoneaJax

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Hello everyone, do any of you know what these black spots growing on my coconut palm are? They look like bacterial colonies to me. So far they are only only on the palms and do not seem to be causing any damage. What do you all think I should do to get rid of them?

 

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3 hours ago, RoystoneaJax said:

@Steve in Florida Is that what you think they are?

I've never had any problems like that.  I would scratch a few off and look at them under an 8-10 power magnifier to see if the problem is insects or fungus.

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If the palm is potted it is probably small enough for you to work on. Make a solution of mild soap (castille or Ivory, not detergent or deodorant) and water. With a soft cloth or sponge, gently wipe down the leaves and petioles front and back. That will kill and disrupt any mites and insect pests. The black spots might be mold/mildew feeding on secretions from aphids. Also, apply an insecticidal drench containing imidacloprid - from Bayer - to the soil. Spider mites do not respond to insecticides, so you may have to hose them down or invest in a targeted miticide. I alternate two every few months during winter/dry season. They can be expensive and must be used outdoors with mask, gloves an a pressure sprayer.

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Meg

Palms of Victory I shall wear

Cape Coral (It's Just Paradise)
Florida
Zone 10A on the Isabelle Canal
Elevation: 15 feet

I'd like to be under the sea in an octopus' garden in the shade.

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  • 2 weeks later...

I want to update this post and say that I showed my local garden center a picture of what was growing on my coconut palm and they confirmed that it was scale. Basically it turns out that what I thought were little colonies of bacteria were actually the female scale bugs which lose their legs and head and stick an appendage into the plant to feed off its sap. They then gave me an insecticide with imidacloprid that I mixed with water and poured into the soil and which made the sap of the plant poisonous in order to kill the bugs. They told me that the insecticide would kill anything that ate from the tree including me and last for a year so I moved it outside to protect my cat who likes to munch on plants. It has been a little over a week and the bugs are all already dead. My questions are how long will the plant remain poisonous enough to kill an animal the size of a cat? Will the scale bugs come back after a year or are they gone for good? And also any ideas on what may have caused the outbreak? I had the plant for a good two and a half months before I noticed anything.

Edited by RoystoneaJax
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I don't know about duration of toxicity for imidacloprid, but I have used dinotefuran on indoor palms for scale issues.  My house panthers don't actually like eating palms or my two ponytails, but one of them loves to play with the ponytail leaves and randomly attacks the leaf tips.  I'd be concerned about it if she actually ate anything.

Regarding scale, my experience with Cycas Revoluta a.k.a. Sago scale is that it can come back the next year.  I got some "donation" sagos from a friend and from three that a neighbor dug up and threw out, and treated them with Dinotefuran soil drench and alternating foliar sprays of Malathion and Acephate.  This killed it all off within about a month, since it was a severe infestation.  The next spring three out of the 19 sagos got reinfested, and two of them were directly across the street from my neighbor's infested-as-white-as-snow sago cluster.  Apparently the "crawler stage" of the bug doesn't move very far, but it could be carried by strong winds or on a bird or squirrel or other animal to take it from plant to plant.  Scale can also stay dormant for a long time, though I don't know how long.

So the short answer is that yes, it's possible that the palm will get reinfested.  Sago scale is notoriously difficult to kill off, and I had 85% success rate with a single soil drench of Dinotefuran.  Palm scale isn't as tough to kill, so there's a good chance that dose will kill it off for good.  But there's a chance of getting reinfested from nearby palms or people or animals carrying scale back into your patio.

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