Western Soapberry Pest

Insect Pest of Western Soapberry

Reported from the Dallas Area

by Dr. Michael Merchant

A new pest to north Texas, the wood-boring beetle Agrilus prionurus, was discovered this summer damaging Western Soapberry trees in the Dallas/Fort Worth area.  The beetle, a native of Mexico, was first discovered in the U.S. attacking native Western Soapberry trees in Bastrop County, Texas in October 2003.  It has since been found in numerous sites in the Texas hill country and other parts of south and central Texas.  It probably arrived in north Texas within the last two years.

Entomologists at the Texas A&M Dallas Research and Extension Center first confirmed the “Soapberry borer” this summer.  It has since been seen by others, at various other sites in the Metroplex.  Infested trees can be identified by probing the bark to see if it easily peels off.  Another infestation sign appears when small patches of bark 1.5 to 3 inches or larger in diameter

are peeled off by squirrels looking for insect larvae.  A heavily infested tree will be completely girdled by the feeding in the sensitive cambium layer just under the bark.

The adult beetle is about one half inch long, shining black and distinctively marked with four small white spots.  It is narrowly cylindrical with tapering wing covers that merge to a point.

The beetle has been highly damaging to Soapberry in central Texas.  According to Arborist Pat Wentworth of Austin Tree Specialists, Soapberry damage was first noticed about three years ago.  Although it has not completely eliminated the tree there, the beetles have caused extensive losses of healthy, mature stands of Soapberry.  So far the beetle appears to be limited to attacking only Western Soapberry, a native tree that occurs in scattered plantings along creeks, and is occasionally used in native landscapes.  The beetle should pose no risk to other landscape trees.

No research has yet been done on control of this pest, but conventional borer preventive sprays may help.  If you believe your tree may already be under attack, a root zone application of imidacloprid (Bayer Advanced Tree And Shrub Insect Control) has been effective in the upper Midwest against similar tree borers.

Article reproduced by permission of the author, Dr. Michael Merchant, Professor and Extension Entomologist, Texas A&M University Research and Extension Center, Dallas.

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