MANAGE FORESTS & LAND

  • FOREST HEALTH: SOAPBERRY BORER

    Mexican Soapberry Borer:
    An exotic pest threatening western soapberry trees in Texas

    Soapberry Tree IllustrationA native of Mexico, the soapberry borer (Agrilus prionurus, Coleoptera: Buprestidae) first was reported in Travis County in 2003. Since then, it has been detected in 49 additional counties including near or within the cities of Austin, College Station, Corpus Christi, Dallas, Fort Worth,

    Houston and Waco (see map).

    As the pest population expands rapidly in Texas, this insect is killing all sizes of soapberry trees larger than 2 inches in diameter. It may eventually threaten western soapberry populations throughout the tree’s range, which extends from northern Mexico to Missouri, and west to Arizona.

    Leaves and fruit of western soapberry, a medium-sized, drought-hardy tree, resemble those of the invasive Chinaberry tree, but the leaves are not double compound and the leaflets do not have serrated (toothed) margins.

    Soapberry borer infestations are similar to those of the emerald ash borer, Agrilus planipennis, another introduced pest that is killing thousands of ash trees in the Midwest. Fortunately the emerald ash borer, a close relative of the soapberry borer, has yet to be found in Texas.

    Infested soapberry trees can be easily recognized by the exposed sapwood that results when birds and squirrels chip off the bark to feed on the larvae, leaving bark chips to accumulate at the base of the tree. A heavily-infested tree will be completely girdled by white larvae feeding beneath the bark. Infested trees will die back from the top and often produce abundant sprouts along the trunk. Trees may take up to three years to die, following the initial beetle attack.

    The adult beetle is about half an inch long, shiny black and distinctively marked with four small white spots on the wing covers. The white larvae are flat-headed wood borers that may attain an inch or more in length as they mature. After feeding beneath the bark, the larvae bore into the wood to complete development and to pupate. The adult leaves a D-shaped exit hole in the bark as it emerges. The insect appears to have no more than one generation per year, with adult beetles emerging from May through August.

    Western soapberry appears to exhibit little resistance to this introduced pest. However, to protect high-value soapberries in your yard, conventional borer preventative treatments may be applied prior to insect attack. One product -- Bayer Advanced Tree and Shrub Insect Control, whic h contains imidacloprid, can be applied to the root zone. Follow directions on the label.

    A new systemic insecticide, emamectin benzoate, sold by Syngenta Corporation under the trade name Tree-äge, is now available and may provide prolonged protection up to two years with a single trunk injection. Unlike the Bayer product, emamectin benzoate is a restricted use insecticide. It can only be purchased and applied by certified pesticide applicators. Systemic insecticides are most effective when applied to soapberry trees prior to beetle infestation, although chemical treatments may save trees in early stages of insect attack if the tree still has sufficient green foliage and bark loss is minimal. No other tree species appear to be attacked by this insect so treatment should be limited to soapberry trees.
     + View the Effects of Soapberry Borer on Leaves and Trees.

     Soapberry leaves and berries

    Soapberry borer

    Soapberry Infestations

    Bark Damage
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