Thorn Bug – Early Spring Pest of South Florida Ornamentals

Numerous plant samples with Thorn bug (Umbonia crassicornis) have landed on my desk this week.  Professionals throughout the county will notice this insect as well.  This is a very interesting, unusual-looking insect!

INTRODUCTION ~ Thorn bugs have been noted in high frequency in the past several weeks (April 2012).  This insect can be found at all times of the year, but is more common in the cooler months of late winter and early spring.

Thorn bug and Sri Lanka weevil damage on powderpuff. Photo: UF Laura Sanagorski

HOSTS ~ Thorn bugs have recently been seen on powder puff trees (Calliandra spp.).  They can also be found on tamarind, wild tamarind, bottlebrush citrus, jacaranda, royal poinciana, and acacia trees.

IDENTIFICATION ~ Thorn bugs blend in with a plant’s foliage and often go undetected.  The sample in the photo to the left was examined for a few minutes before this insect was noticed.  The color is green or yellow with brown or reddish markings.  This insect can be identified by the adult’s pronounced thorn-like or claw-like horn.  Juvenile versions of this pest look quite similar but will be smaller in size and have three less-prominent horns.  Generally, one will find various stages of the thorn bug’s life cycle on one branch.

Thorn bug. Photo: UF Laura Sanagorski

LANDSCAPE MANAGEMENT ~ The population of this insect will drop on its own as warmer months approach.  Thorn bugs, like whiteflies and thrips, have piercing / sucking mouthparts that allow them to feed on the nutrients of a plant.  They also produce honeydew, which can support the growth of sooty mold.  Serious damage is not generally associated with this insect, making treatment generally unnecessary.  Horticultural professionals who determine that treatment is required will be able to manage this insect with horticultural soaps and oils, or other insecticides (such as those in the neonicotinoid family) labelled for use on the plant of concern.  Physical removal, such as with a heavy spray from a hose, will also greatly reduce this insect’s population.

~ Download a Printer-friendly version of this fact sheet here ~

References and Further Reading ~ 

Culbert, D.  (2004). Powderpuffs and thorns.  UF / IFAS Okeechobee County Extension Service.  Available at: http://okeechobee.ifas.ufl.edu/News%20columns/Powderpuffs%20&%20Thornbugs.htm

Mead, F.W., & Fasulo, T.R. (2004).  Featured Creature: thorn bug.  Florida Department of Agriculture and Consumer Services, Division of Plant Industry.  Available at: http://entnemdept.ufl.edu/creatures/orn/thorn_bug.htm

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2 responses to this post.

  1. Posted by Louise Niemczyk on July 14, 2012 at 10:48 PM

    July 14,2012 … My powder puff tree has at least 50 of these thorn bugs. As cooler weather is not around the corner I’m not looking forward to fighting these off in my chemical free butterfly garden. Any suggestings would be appreciated.

    Reply

    • Louise,
      Thorn bugs generally don’t cause enough damage to warrant any type of treatment, so I wouldn’t worry too much. If you’d like, you can remove the thorn bugs with a strong spray from your garden hose. You can also remove them by hand and dispose of them.

      Reply

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