Introduced Pests Outreach Project

Giant Woodwasp

(Click on an image below to see the captioned full-size version)
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5

Scientific Name: Urocerus gigas
Common Names: Giant Woodwasp, Banded Horntail, Greater Horntail

Known Hosts:
Urocerus gigas attacks 5 or more genera in the family Pinaceae including Douglas fir (Pseudotsuga), fir (Abies), larch (Larix), pine (Pinus), and spruce (Picea). For a complete listing of hosts see the USDA Mini Risk Assessment for Giant Woodwasp, Urocerus gigas:

Key ID Features and Life Cycle:
Adult wasps are between 10 to 40mm (0.5 to 1.5 inches) long with a cylindrical body. Adults have a spear-shaped plate (cornus) at the tail end.
Females have a yellow abdomen with a black stripe in the middle. The female has an ovipositor on the end of its abdomen for egg-laying. (Figure 1)
Male adults are smaller than females. The abdomen is yellow at the center with black at the base and tail end. (Figure 2)
In Great Britain adult flight was observed between June and early October.
Females lay up to 350 eggs after emergence. (Figure 3)
Larvae are creamy white, cylindrical grubs up to 30 mm (1 1/4 inches) long with a dark spine at the end of the abdomen. (Figure 4)
The larval stage usually lasts for 1-3 years before mature larvae pupate near the bark surface.

Signs of infestation:
Tunnels in the wood ranging from 15 to 75 cm (6 to 30 inches) in length that are tightly packed with frass. (Figure 5)
Round exit holes 3-8 mm (1/8 to 3/8 inch) in diameter are visible on trees trunk.

Similar species:
There are 23 native species of siricids in North America. The following publication provides a key for distinguishing those species:
NM Schiff. SA Valley, JR LaBonte, and DR Smith. 2006. Guide to the Siricid Woodwasps of North America.USDA Forest Service

Fact sheets and references:
USDA Mini Risk Assessment for Giant Woodwasp, Urocerus gigas:

Greater horntail wasp (Yellow-horned horntail) - Urocerus gigas (L.)
From: Kolk A., Starzyk J. R., 1996: The Atlas of Forest Insect Pests

Walker, K. 2005. Yellow-horned horntail (Urocerus gigas). Pest and Disease Image Library.

Video of Giant Woodwasp laying eggs

Host and survey maps - Purdue University Pest Tracker

last reviewed December 18, 2014

Massachusetts Department of Agricultural Resources
Massachusetts Introduced Pests Outreach Project is a collaboration between the Massachusetts Dept. of Agricultural Resources and the UMass Extension Agriculture and Landscape Program. This website was made possible, in part, by a Cooperative Agreement from the United States Department of Agriculture's Animal and Plant Health Inspection Service (APHIS). It may not necessarily express APHIS' views.