These invasive insects were first detected in Pennsylvania in 2014. Spotted lanternflies (SLF) are exceptional stowaways/hitchhikers, and it is precisely this type of behavior that accounts for their rapid spread to fourteen additional states. At the time of this writing (May 2023), they are found in Connecticut, Delaware, Indiana, Maryland, Massachusetts, Michigan, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, Virginia, and West Virginia. Many experts believe that that number will climb within the next year to include states further south along the coast. By 2050 they are expected to be established all the way to California.
SLF produce one generation a year, which includes an overwintering egg stage, four nymphal stages (instars) and an adult stage.
- May-June: Egg hatching and 1st instar nymphs. These nymphs have black and white spots and are about ¼" in size. They will retain this coloring and remain this size until the 4th instar. They can be mistaken for ticks in these nymphal stages.
- June-July: 2nd instar nymphs
- June-July: 3rd instar nymphs
- July-September: 4th instar nymphs. The nymphs have grown to about ¾" at this point and have red and black coloring with white spots.
- July-October: Adults. When they reach adulthood, SLF will be about 1" long with a wingspan of about 2". They have pinkish-brown wings with black spots and a yellow abdomen with black stripes. When they fly, the wings open to reveal bright red hind hindwings.
- September-November: Egg laying. Egg masses are laid in 1" long segmented rows. The female covers them with a white putty-like substance that becomes pinkish-gray and then a dull brown. Eventually the covering will crack a little and look a great deal like smears of mud.
Despite the name, SLF are True Bugs from the order Hemiptera. Hemiptera have sucking mouth parts, called proboscis, which work like straws. They use their proboscis to pierce into plant parts and suck out the sap. Although the feeding behavior of Hemiptera does not kill plants outright, it can weaken them to the point that they fail to thrive, produce poor or no fruit and blooms, wilt, defoliate and then die. Since SLF are swarm feeders, with hundreds of individuals in multiple life stages on a plant, such an onslaught can be devastating. The preferred host of SLF is another invasive species - the Tree of Heaven (Ailanthus altissima), but they've been known to feed on hundreds of species of plants. They are especially damaging to grapes, both cultivated and wild).
SLF have become a serious problem because they are so difficult to control. Their swarm behavior, including their mobility and quick adaptability, is at the heart of it. They are always moving in search of food to feed the swarm. As nymphs and adults, they are impressive jumpers and as adults they can also fly. They've been known to travel miles on their own, but they prefer to hitchhike on items humans use. For instance, they will jump into carts, fly into trucks, attach themselves to bags and hide in clothing. Before they are seen they have been transported. Because they look like smears of mud and people don't notice them, their egg masses are moved around in the same way. Another control factor is that the swarm protects itself by quickly vacating an area that's being sprayed and will often return when the spray dissipates.
To get a grip on SLF, it takes a multi-pronged, diligent effort that addresses each life stage. SLF produce one generation a year, which includes an overwintering egg stage, four nymphal stages (instars) and an adult stage. Egg cases need to be scraped off any surface they are found on and disposed of in such a way that they cannot survive. This can be done by putting them into a plastic bag filled with hand sanitizer or spraying them with suffocant like dormant oil. In the other stages, trunk, branch and foliar sprays will work to some extent but will probably need to be reapplied aggressively. Sticky traps and tree bands will work but must be installed carefully so that they don't trap birds or other wildlife and monitored closely so that they do not fill up and become a bridge for other SLF. Neem oil, horticultural and dormant oils, insecticidal soaps and pyrethrins can be used as sprays. Fungicides as a pro-active pretreatment are a good idea, especially biologicals like Burkholderia spp. strain A396 and Beauveria bassiana.