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SLF is a significantly important economic and lifestyle pest to residents, businesses, tourism, forestry, and agriculture. Specialized mouth parts (the beak) of both nymphs and adults pierce through plant tissue and suck sap directly from the phloem of leaves, stems, branches, and trunks. First through third instar nymphs feed on young shoots of perennial and annual plants while the stronger-beaked fourth instar nymphs and adults are able to feed directly in older tissue.

Feeding damage may both encourage secondary invaders and, though unknown at this time, encourage the spread of pathogens.

Because spotted lanternfly, a phloem feeder, consumes large quantities of a plant's sugary sap looking for nitrogen and amino acids, it expels large quantities of excess sugar (honeydew). Honeydew—often misidentified as sap—shows up on outdoor equipment, decking, and vehicles as well as pets and your clothing and hair, and also acts as a growth medium for sooty mold. No life stage of the SLF feeds directly on fruit, but South Korean grape and tree fruit growers found their crops unmarketable due to the growth of sooty mold on the skins. Sooty mold also inhibits the photosynthetic capacity of leaves and makes fruit unmarketable. Under high population pressure in residential areas in the PA quarantine zone, the volume of honeydew produced has some residents feeling like prisoners in their own homes, from late summer until the first hard freeze killing adult SLF. Honeydew can also produce an odor of fermentation. This combination of honeydew and sooty mold production has a negative effect on the quality of life for residents in the quarantine zone.

Feeding by SLF may cause

  • Oozing
  • Wilting
  • Defoliation
  • Dieback
  • Yield loss or quality reduction
  • Reduction of cold hardiness
  • Plant death
Spotted lanternfly adult feeding, close-up
Spotted lanternfly adult feeding on a twig. The orange round objects are the antennae, located below the black eyes. Photo: NYSIPM Staff.
Spotted lanternfly adults massing on a tree
Spotted lanternfly adults massing on a tree. Photo: Pennsylvania Department of Agriculture.
Spotted lanternfly adults massing on an apple tree
Spotted lanternfly adults massing on an apple tree. Photo: Erica Smyers, Penn State.
Spotted lanternfly adults massing on grape
Spotted lanternfly adults massing on grape. Photo: NYSIPM Staff.
Honeydew produced by spotted lanternflies covers a stairway
Honeydew produced by spotted lanternflies covers a stairway. Photo: Barbara Bower, Homeowner.
Honeydew produced by spotted lanternflies on foliage, with an adult spotted lanternfly
Honeydew produced by spotted lanternflies on foliage, with an adult spotted lanternfly. Photo: NYSIPM Staff.
Sooty mold on grape leaves
Sooty mold on grape leaves. Photo: Erica Smyers, Penn State.
Spotted lanternfly adult and a wasp on a tree
Spotted lanternfly adult and a paper wasp on a tree. The presence of the fermenting odor and honeydew can attract other nuisance insects. Photo: NYSIPM Staff.
Spotted lanternfly adult and a yellowjacket on a tree
Spotted lanternfly adult and a yellowjacket on a tree. The presence of the fermenting odor and honeydew can attract other nuisance insects. Photo: NYSIPM Staff.

In the video above, you can see spotted lanternflies excreting honeydew. Video: Erica Smyers, Penn State.