October 11, 2006

Feature Article - for release the week of October 15, 2006

Dan Culbert - Extension Horticulture Agent

 

 

 Goblins Beware: This Skeleton has six legs

Earlier this summer our office had one of those fun “visitors” that agents love to talk about.  I set this one aside for a Halloween column – so it’s time to rattle my bones and tell you about this featured creature!

 

I’ve seen beetles with long antenna before, but the color of this critter was different from anything I had ever seen.  At first I was worried, as there have been many recent reports of longhorned beetles in other areas of the US and some of these are exotic invaders that destroy both urban trees and forests in other parts of the country.  It got me scared!

 

Our Master Gardeners and I poured over many different references and came up clueless.  Finally we happened to look at a new poster, “Scary Insects and Creepy Crawlers" that is available from the UF/IFAS Extension Bookstore.  And right in the middle was a picture of our U.C.O. (Unidentified Creepy Object), a Skeleton Beetle.

 

 

 

Actually “Skeleton beetle” is a less commonly used name for a Longhorned beetle known as the Cottonwood Borer.  Those true entomologists who want to be proper Greeks (or is it geeks) will call it Plectrodera scalato.  Since there are not too many Cottonwood trees growing in South Florida, I had to wonder what this creature was doing in our area.

 

This beetle was big enough to cover a quarter!  It was more than an inch long and about a half-inch wide.  The color was mostly black but it has lines of cream-colored hair all over it that makes it looked like a skeleton.  With its irregular black patches, six long legs, big mandibles and two very long antennae, this beetle was ready for Halloween! 

 

 

Lifecycle of the Skeleton Beetle

 

The Cottonwood borer can be found anywhere across the eastern US, but is more common in the South. And since it attacks also attacks willow trees, I could now understand why it was found here in southern Florida.

 

Eastern Coastal Plain Willows (Salix caroliniana) are shrubby native trees that grow in moist soils found near freshwater ponds.  They are our only locally native willow tree that would be of interest to this beetle.  (Come to think of it, we do have a “little” freshwater pond located somewhere near the south end of Okeechobee county, right?)

 

The beetle itself is of little consequence to our native willows.  But when these skeletons come out of their closet, it’s not around Halloween, but in midsummer.  After chewing up a few branches on the trees, they drop to the base of a willow (or cottonwood) tree, where females deposit eggs in small pits gnawed in the bark.

 

Skeleton beetle grubs hatch from the eggs in 16 to 18 days, and these seldom seen larva bore down into the inner bark, looking for a large root, just in time for Halloween.  They continue to feed inside the roots until April to June.  Pupation occurs in their “skeleton gallery,” and lasts for about 3 weeks.  Some larvae can complete development in 1 year, while others require 2 years.  The new skeleton beetle adults will emerge by chewing exit holes through their pupal chambers and burrow through the soil. 

 

 

 

 

 

Why worry about these Skeletons?

 

If you are a willow or cottonwood tree, an infestation of these wood-boring grubs could weaken your roots.  The adult beetle feeding on the leaves and twigs may notch small branches which could then break off in the wind.  However, damage is rarely serious unless you have a lot of willows (or cottonwoods) growing in a nursery, or are replanting these trees in wetland renourishment projects.

 

 

The real issue with long-horned beetles is with some of their relatives.  They are illegal aliens that have come into this country as grubs buried deep in wooden pallets or packing material.  Since these Asian natives have no natural enemies,  they have the potential to ruin a lot of forests or groves.

 

 

 

 

The Asian Longhorned Beetle (ALB)  (Anoplophora glabripennis) attacks many kinds of living hardwood trees.  It has the potential to destroy northeastern hardwood forests.  So far it has been found only in the vicinity of New York City, Chicago, and Toronto, where it was unintentionally introduced in wooden crates from China . 

 

The ALB has not been found in Florida.  If you see a black beetle that resembles the ALB, don’t squish it!  Instead, capture it intact, and bring it to our office for identification.  None of these beetles can sting, and while they could pinch a finger with their jaws, they are not strong enough to break the skin.

 

Another relative that poses a threat is the Citrus Longhorned Beetle (CLHB), which has been reported once in Georgia and another time in Washington State. In the case of both the ALB and the CLHB, cutting down infested trees is the only real control measure.

 

I’ve placed pictures and more information on our Okeechobee web page, http://okeechobee.ifas.ufl.edu.  If you need additional information on the Skeleton Beetle or other long-horned beetles, please email me at indianco@ufl.edu  or call us at 863-763-6469.  Local residents can stop by our office at 458 Hwy 98 North in Okeechobee.

 

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Trade names, where used, are given for the purpose of providing specific information. They do not constitute an endorsement or guarantee of products named, nor does it imply criticism of products not named. The Florida Cooperative Extension Service - Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information, and other services to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin.  Florida Cooperative Extension Service / IFAS / University of Florida.  Millie Ferrrar Chancy, Interim Dean Last update: 11/07/2011 .  This page is maintained by Dan Culbert 

references

Anonymous. Cottonwood Borer, Plectrodera scalator.  From: Insects and Diseases of Trees in the South.  USDA Forest Service - Forest Health Protection. R8-PR16. 1989.  http://www.forestpests.org/southern/cottonwoodborer.html 

Carolina willow, Coastalplain willow.  Gainesville: UF/IFAS Center for Aquatic and Invasive Plants, 2011.  http://plants.ifas.ufl.edu/node/392

 Drees, B.M. and Jackman, John.  Cottonwood Borer.  In: Field Guide to Texas Insects, (c) 1999 College Station: Texas A&M University, 2005 http://insects.tamu.edu/fieldguide/bimg177.html

Foltz, John and  Thomas, Michael C.  Asian Longhorned Beetle - A Threat to Florida Trees? (Pest Alert)   UF Dept of Entomology & Nematology,11/10/1998.. http://entnemdept.ifas.ufl.edu/foltz/eny3541/alb/alb.htm 

Gyeltshen, Jamba and Hodges, Amanda.  Citrus Longhorned Beetle (EENY-357) Gainesville: UF/IFAS Dept. of Entomology & Nematology, Featured Creatures website, 9/2005. http://edis.ifas.ufl.edu/in633 

McKinney, Russ,  Duerr, Don  and Haugen, Dennis.   Asian Longhorned Beetle vs. Cottonwood Borer.  Newtown Square, PA: Northeastern area office, USDA Forest Service, 4/2000.  http://www.na.fs.fed.us/fhp/alb/pubs/alb_cb/alb_cb.htm 

Weihman, Scott & Medley, Jane.  Scary Insects and Creepy Crawlies poster (SP 423).  Gainesville: UF/IFAS Extension Bookstore, 2006. (The photo of the skeleton beetle was taken by Charles Lewallen.) http://ifasbooks.ufl.edu

Stamp out this beetle!