Kelly Jackson
Christian County Extension Office
It’s Snowing – Insects?
Asian woolly hackberry aphids are distinctive insects. A covering of thin bluish-white waxy filaments causes these small sap-feeding insects to standout on foliage. They can look like large wet snowflakes, especially as they drift through the air. This aphid has another dimension: excretion of large volumes of sticky honeydew (insect waste). Foliage and branches of infested trees, as well as surfaces beneath them, become wet and shiny. These surfaces ultimately may turn black from the growth of sooty mold fungi. Woolly aphids do not appear to cause significant injury to otherwise healthy trees. However, dripping honeydew and subsequent accumulations can be objectionable in some situations.
Controlling this pest on large trees is a challenge. Many people opt to just do nothing and live with it and, since the aphid does no long-term damage to the tree, that is perfectly acceptable. But where the honeydew drifts and the sooty mold stains cars, deck furniture and everything else below, homeowners may want to take action. A permanent solution is removing the tree but of course that has other negative side effects such as loss of shade, depreciation of home value and loss of habitat for wildlife. Insecticides are another option. Asian wooly hackberry aphids can be controlled by soil-applied applications of systemic insecticides containing imidacloprid (i.e., Bayer Advanced Tree and Shrub Insect Control or Fertilome Tree and Shrub Systemic Insect Drench).
Drenches are applied by adding chemical to water (a specific quantity using a formula based on the diameter of the tree trunk) and pouring the contents around the root area. These products are applied annually in late winter or early spring and can be costly, especially for large trees. Results can be erratic. For smaller trees, insecticidal soap has been used as a foliar spray to provide some control of the aphid, as well as in an effort to wash away the “dew.”
