Shade Tree Notes Blog

By Laura Sarzaba

It's winter, and you finally have all the time you wished you had during the growing season to scour your clients' properties for plant health care concerns. Of course, it's a bit trickier this time of year, but kind of a fun challenge!

Spotted lanternfly is on a lot of minds downstate. Ailanthus is living up to its reputation as the preferred host, but we have seen infestations on Maples (especially Silver, Norway and Red) and Willows as well. Honeydew dripping from infested trees during the growing season can get very heavy, which is of particular concern for trees overhanging structures, gathering places and parking areas.

Looking for egg masses is of course one strategy for scouting for this pest. However, the majority of egg masses are in the upper canopies of trees, and they can blend into the bark pretty well. Another strategy I've found helpful is to look for sooty mold on understory plants below common hosts. The presence of sooty mold on plants that don't typically suffer from piercing/sucking insect infestations can be a telltale sign of an infestation in an overstory tree. For instance, sooty mold on the leatherleaf viburnums in this photo are a good clue that there may be a lanternfly infestation in the overstory Silver Maple -- so I can give the client a head's up and know to monitor it closely in the summer.

Aphid infestations can produce similar issues with sooty mold on understory plants, with Lindens and Birches as common hosts.

PHC 101: sapsucking insects

Sapsucking insects such as spotted lanternflies feed by drinking the sap of plants using piercing/sucking mouthparts. This can harm trees and shrubs in a few ways. In the most direct case, the loss of sap leads to a loss in overall vigor. The insects can also act as vectors of destructive diseases, such as bacterial leaf scorch. Finally, many sapsucking insects produce copious amount of honeydew (sticky excrement) during feeding -- and that becomes a surface for black sooty mold to grow. When leaves are covered in thick sooty mold, photosynthesis is disrupted and energy production declines. It also looks terrible and is a big nuisance when it gets on surfaces like decks and outdoor furniture.