Bug FAQTwo-horned Gall Wasp
Dryocosmus dubiosus · Order: Hymenoptera · Family: Cynipidae
Source: Wikipedia
These galls grow on oak trees in California and can harm the trees, often being mistaken for fungal or beetle damage.
Source: Wikipedia
How to recognize it
The gall that forms after the eggs hatch resembles a pair of bull's horns.
Source: Wikipedia
Is it a pest in the house?
Damage from the leaf-galling generation is often confused with fungal twig blight or oak twig girdlers.
Source: Wikipedia
How to get rid of it
UC Integrated Pest Management advises that this gall-wasp damage is frequently misidentified as fungal or beetle injury.
Source: Wikipedia
Where it lives
The wasp creates galls on oak trees in California, North America.
Source: Wikipedia
Life cycle
After the eggs hatch, the developing gall takes on a shape that looks like a pair of horns.
Source: Wikipedia
Where it comes from
It is found in California, North America.
Source: Wikipedia
Lookalikes
The leaf-galling damage can be mistaken for that caused by fungi or certain beetles.
Source: Wikipedia
Where it is found in the US
Recorded in 42 of 51 states and DC. Most records: California, Ohio, Virginia, Massachusetts, Pennsylvania, New York, Texas, New Jersey.
Darker = more records. Counts are museum and citizen-science records, not population size.
Source: GBIF
Status: native in North America; native in United States. Source: iNaturalist
Months it is reported in the US
Source: GBIF
More photos
Questions people ask
What does the gall caused by the two-horned gall wasp look like?
The gall resembles a set of bull's horns on the leaf or catkin.
Source: Wikipedia
Which oak species are affected?
Coast live oaks and interior live oaks are the hosts.
Source: Wikipedia
How can I manage the damage?
University of California IPM notes the damage is often misidentified, so proper identification is the first step in management.
Source: Wikipedia
Same family (Cynipidae)
Sources
- Wikipedia: https://en.wikipedia.org/wiki/Dryocosmus_dubiosus
Look it up elsewhere: GBIF · iNaturalist · BugGuide · Wikipedia
Text written 2026-10-23 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-22.