If the leaves or needles on your tree develop a coating that looks velvety but feels crusty and is a dark gray, then it is likely that your tree has developed black sooty mold. What feels like a layer of coating is really a growth of black molds or fungi. If you pick up the leave and rub it, the coating comes off quite easily.
Black sooty mold just grows on the surface of the plant and in most cases does not harm it. The good news is that this type of mold is really more an aesthetic issue than a matter of life and death for your tree. In severe cases it shows enough black growth to keep sunlight away, interfering with photosynthesis. In cases like this, you’ll see smaller and duller shoots, fruit, needles and/or leaves. Also, the mold can hold stomates closed, interfering with respiration.
Sooty mold growth is a by-product of the influence of sucking insects. Many insects that drink sap feed from stems and leaves of shrubs and trees. Often you’ll see a thick, syrupy runoff from these trees, known as honeydew. The sooty mold grows on the honeydew. While aphids are one of the most common producers of honeydew, soft scales, planthoppers, leafhoppers, psyllids, whiteflies and mealybugs also produce it. Plants that host these insects are more likely to be susceptible to developing the mold. Birch is a common host.
If you think you see black sooty mold on your trees, give one of our certified arborists a call. We will come out and identify the insect that is causing the mold. The best way to control this mold is to get rid of the insects involved. Pruning to improve airflow also helps. We have a variety of chemical and organic treatments to help keep those bugs away from your trees. Call today to get a consultation of your yard and a proposed treatment plan.