Q&A: When Will Spotted Lanternfly Eggs Hatch?

Spotted Lanternflies are black with white spots when they first hatch
Immature Spotted Lanterflies are black with white spots when they first hatch in mid-April to May. Photo: Lawrence Barringer, Pennsylvania Department of Agriculture, Bugwood.org

Q: When will Spotted Lanternfly eggs hatch? We’ve had such warm spells this season that I worry it’ll be early.

A: Spotted Lanternfly (SLF) egg hatch, like the activity of many insects, is greatly dependent on temperature. Predictions for egg hatch in an average year begin around mid-April but can continue into May, so while it may not be early per se at this point, it still will be soon. As such, this is your last opportunity to be vigilant for egg masses to squish before the active, hopping, hard-to-catch juveniles appear.

Don’t panic – juveniles cause little plant damage to gardens when young – but eliminate any egg masses within reach if possible because this is a serious agricultural pest (vineyards, mainly) and it might help you avoid an inundation of nuisance lanternflies later. To be fair, many eggs are laid high in tree canopies, making them inaccessible, but others can be laid on piles of stone, fencing, car hubcaps, grills, outdoor furniture, honey bee hive boxes, and so on.

Gray patches that look like dried mud are Spotted Lanternfly egg masses
Spotted Lanternfly egg masses on wood. Photo: Emelie Swackhamer, Penn State University, Bugwood.org

Be advised that the quarantine zones in Maryland have recently been expanded, and records indicate that the abundance of this pest has grown in our central counties. Check our Spotted Lanternfly web page and information updated on the Maryland Department of Agriculture website for more details. An MDA entomologist presented a refresher webinar about SLF this past winter, which you can find on the UMDHGIC YouTube channel as “Spotted Lanternfly Update from MDA.”

Spotted Lanternfly webinar (1 hour, 11 minutes)

If you haven’t seen Spotted Lanternflies in your neighborhoods yet, be prepared to see them in the next year or two as the population expands. I don’t want to scare you, just make you aware this will probably be something you’ll have to experience sooner or later, and I definitely discourage the use of any pesticide to combat this insect if its use can be avoided. Pesticides used to kill SLF have impacts on other insects and organisms and we don’t want to contribute to ecosystem damage by using them when the SLF damage done to most garden plants will be minimal.

By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun and Washington Gardener Magazine. Read more by Miri.

Have a plant or insect question? The University of Maryland Extension has answers! Send your questions and photos to Ask Extension. Our horticulturists are available to answer your questions online, year-roundYou can also connect with your local County/City Extension Office and Master Gardener local programs.

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