The old saying “There is always something new” could not be more true when it comes to exotic invasive pests. We often talk about the emerald ash borer and viburnum leaf beetle, but not today. Today’s exotic invasive pest lesson is on the spotted lanternfly. 

The SLF hails from the Asian countries of China, India, Japan, South Korea and Vietnam, and was first detected in Pennsylvania in 2014. Since then, it has spread to New York and Delaware — but no Midwest states.

The preferred host for SLF is Tree of Heaven. Now, for those of you familiar with Tree of Heaven, you may be excited about a new biological control agent for the tree, but unfortunately, SLF also likes to feed on many of our common fruit trees, oak, walnut, willow, maple, sycamore, poplar and especially grapes. Both the immatures (nymphs) and adults feed on plant sap, reducing photosynthesis and the vigor of the host plant, and producing large quantities of honeydew (liquid insect poop). The honeydew promotes the growth of a sooty mold fungus much like we see with aphids, whiteflies and soft scales.

While sooty mold won’t kill the tree, it can make it very unsightly. As far as we know, SLF doesn’t kill trees, but it does weaken them and predispose them to lethal canker sores and wood-boring insects.

The adult SLF is a fairly large insect, about 1 inch long and a half inch wide, and is quite colorful. It has light-brown forewings with black spots and a scarlet hindwing with black spots at the front, and white and black bars at the rear of the wing. Nymphs are black when young, but then turn red when older. The egg masses, which are laid on the bark of Tree of Heaven, are yellowish-brown with a gray, waxy coating resembling a patch of mud.

The SLF is not a particularly strong flier and can also walk and jump. However, long distance spread is facilitated by people moving infested host material or objects containing eggs masses. Doesn’t that sound familiar — like the gypsy moth and emerald ash borer?

The females lay their eggs on host plant surfaces, as well as on nonliving materials such as bricks, stones, dead plants, swingsets, boat and camper trailers, etc. Once the eggs hatch, in late July, nymphs and adults begin feeding, focusing on Tree of Heaven and grapes. While feeding, nymphs and adults will congregate in large numbers and are easy to see at dusk or night as they move up and down the tree trunk. During the day, they tend to congregate near the base of plants and are harder to see.

If you do observe an insect fitting this description and/or feeding habits, be sure to report it to your county Extension office or the Illinois Department of Agriculture. Get familiar with the SLF and be on the lookout. The first line of defense against any invasive is preventing its spread. Knowing where the insect is currently found can be very helpful in limiting its movement to other areas.

Miller is a horticulture professor at Joliet Junior College in Joliet, Ill., and a senior research scientist in entomology at The Morton Arboretum in Lisle, Ill. Email your tree questions to him at [email protected].