Nature’s Spooky Trees

HRI Research • March 3, 2020

NATURE SERVES UP MORE THAN CRISP FALL LEAVES FOR HALLOWEEN!

It’s fall! The weather suddenly cooled, and fall is here! In between sipping pumpkin lattes and pumpkin patching, you may have noticed some changes in the trees – more than just the standard fall leaf colors and leaf drop. I’m talking about the webbing that pops up every fall in tree canopies. Who is responsible for this mysterious, spooky (and seasonal!) tree décor? It’s none other than the fall webworm.

Fall webworms themselves aren’t very striking in appearance, but they are showstoppers when it comes to their nest. Some even get be two to three feet in size!

Nondescript, white moths (the adult stage) emerge in summer, after overwintering under debris in a cocoon, and females begin laying eggs on leaves. Eggs hatch in about a week. The larvae are small-ish, fuzzy caterpillars, about an inch in length. Over 100 common landscape trees have been documented as host plants, but they seem to prefer black walnut, ash, hickories, and oak. The caterpillars live in a colony…a colony that weaves a beautiful web!

The caterpillars eventually eat all the leaves in the safety of their web and have been known to wander out at night time for feeding if the nest is barren. Eventually the caterpillars mature and pupate in the fall, starting the cycle over again.

No need to worry about damage to the tree. Even though some webs are large, the fall webworm rarely kills a tree. But, of course, the aesthetics of the tree will be impacted, and maybe that’s not such a bad thing…depending on how big a fan you are of creepy, ghostly things.

It’s probably a little late in the year to find any active fall webworms at this time, but their webs should persist through Halloween; think of it as mother nature’s spin on seasonal decor!

Dr. Jill Calabro
HRI Science & Research Director

Photo courtesy J. Calabro, HRI.

admin's blog

Share This Post

By Jennifer Gray • October 12, 2026
Urban landscapes can be important refuges for native bees and other pollinators. This talk covers why bees are critical for biodiversity and food security, why bee populations are declining, and how the gardening public can help by incorporating woody landscape plants to provide nectar, pollen, nesting sites and materials, and other resources. Following a brief overview of pollination ecology, we’ll “meet the bees”, and then discuss recent HRI-funded research that identified top native and non-native “bee magnets” amongst woody ornamental plants. The talk also explains why artificial bee “hotels” can become death traps and suggests better ways to create bee nesting sites through ordinary gardening practices. Attendees will receive PDF handouts and other information helpful for teaching others about the best trees and shrubs for bee conservation.
Horticultural Research Institute tHRive web series logo with green, red, and yellow icon
By Jen Gray • August 12, 2026
CABI and USDA APHIS are collaborating on the biological control of the box tree moth using parasitoids from Asia. Several parasitoid species are currently under consideration for introduction into North America and Europe. One of these parasitoids arrived in Europe on its own and has begun controlling the moth on both planted trees and in wild boxwood stands. The webinar will describe the spread and impact of this adventive parasitoid in Europe and present efforts to assess the potential of this species and others as biological control agents in North America.
HRI Leadership Academy logo with multicolored flower icon and text “An AmericanHort & HRI Initiative”
By Jennifer Gray • June 30, 2026
Meet the HRI Leadership Academy Class of 2027. This intensive year-long program equips green industry leaders with strategic insight and business acumen.
Show More