Extension Service: Palm problems likely came from Wilma versus young buds or overpruning

Are you seeing all of the new “Compass” queen palms —the ones with their heads leaning south at a slight angle and some with their “heads” all the way over?

We have about a dozen or so queens with this exact symptom in my neighborhood. The symptoms didn’t show up until mid-January. They all started leaning to the south, the main direction that Hurricane Wilma was blowing back on Oct. 24. Often the palms were overpruned, which may have contributed to their wind vulnerability because the supporting shock-absorbing capacity of the “boots” and attached fronds had been pruned away. I’m not seeing any other obvious signs or symptoms to indicate other diseases or problems.

Sometimes boron deficiency will cause similar symptoms on queen and royal palms, and for more information on that, you can call the Master Gardener Clinic at our office, 353-2872 or check this Web site: collier.ifas.ufl.edu/Horticulture/CommHortPubs/Boron%20DeficiencyOct05.pdf

But these queen palm heads are all crooked over in the same direction, which points to a wind event in this diagnostician’s mind.

I’ve been called to look at this same problem in several communities, including Marco Island. As landscaper Michael Alexander put it, “It is as if they got their heads slammed in a door!” I think that the buds were in a particularly tender stage of growth when they were assailed by Wilma. The puzzling symptom delay, not until mid-January, may be due to the weight of the head being shifted to the new portion of the trunk (internal) that had been damaged back on Oct. 24. That’s my theory. These palms may survive if the head does not exceed more than a 45-degree angle, but aesthetics may still call for their removal. I also expect that we will see more post-poned Wilma damage to plants as the summer progresses. “

Other landscape insect activities include mahogany webworm attacks on some large trees back in mid-May. The frass was raining down and reminded me of gypsy moth outbreaks up north. Unlike gypsy moth caterpillars, which are the “cows” of the insect world and completely devour tree canopies in a few weeks, the mahogany webworms had devoured less than 20 percent of the trees’ foliage. Since the yellow caterpillars with longitudinal black and white stripes were pretty much finished chewing and ready to pupate, I advised the owner to wait it out or, if the frass got too deep, try a caterpillar specific product containing B.t. or spinosad.

The chemistry from these products is based on bacterial derived toxins, which kind of sounds like something from Saddam Hussein’s war chest, but they primarily target Lepidoptera and tend to avoid collateral damage to the good bugs, the predators and parasites, which may also be killed when a broad spectrum insecticide is used. The mahogany webworm has repeating generations, but the first generation is reported to be the most damaging.

We are also seeing more of the snowbush inchworm, which reached outbreak proportions last year. Landscaper Mike Malloy reported good inchworm control by pruning back the new growth last year. Seems like the little inchworms didn’t climb back up onto the bushes and the shrubs flushed out without the use of an insecticide.

However, because this insect has repeating generations, it was active until early August last year. You may want to consider the treatment recommendations above for the mahogany webworm if you don’t want to continually prune your snowbush hedge. For more pictures and details on this defoliator, see: collier.ifas.ufl.edu/Horticulture/Snowbush%20Caterpillar.htm

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Doug Caldwell is the commercial landscape horticulture educator with the Collier County Cooperative Extension Service. E-mailor call 353-4244, ext. 203. For updates on the Southwest Florida Horticulture Learning Center and more landscape pest management details, visit collier.ifas.ufl.edu.

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