Rough Bulletgall Wasp

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Taxonomy

Domain	Eukarya
Kingdom	Animalia
Phylum	Arthropoda
Subphylum	Hexapoda
Class	Insecta
Subclass	Pterygota
Infraclass	Neoptera
Superorder	Holometabola
Order	Hymenoptera
Suborder	Apocrita
Superfamily	Cynipoidea
Family	Cynipidae
Subfamily	Cynipinae
Tribe	Cypinini
Genus	Disholcaspis

Scientific Name

Disholcaspis quercusmamma

Common Name

oak rough bulletgall wasp

Compiled by Whitney Cranshaw, Colorado State University:

Disholcaspis quercusmamma (Walsh)
Hymenoptera: Cynipidae

Hosts

Oaks

Bur oak (Quercus macrocarpa)

Swamp white oak (Quercus bicolor)

Damage and Diagnosis

Gall made by rough bulletgall wasps.

Rough bulletgall wasps produce a woody, generally rounded gall on bur oak, with a slight point. Very heavy infestations can occur that largely cover twigs, reducing growth rate of the tree. Following leaf drop, the galls can be highly conspicuous. The galls also exude a honeydew-like sweet material that is attractive to bees and wasps and fosters growth of sooty molds.

Life History and Habits

Females emerge in late October and early November, after a hard frost. (A small circular hole in the gall indicates emergence.) Eggs apparently are laid in the terminal growth during the fall. winged and wingless forms are produced; males apparently are unknown.

In late spring, the developing insect stimulates a pocket of stem tissue to produce a large rounded gall, in which the young wasp develops. Galls are pale brown and soft in early stages, later darkening and hardening. Only a single wasp develops in each gall, although sometimes other insects (inquilines) also share the gall. The larva pupates within a small cell in the center of the gall, emerging in early fall. There is one generation per season.

Management

None have been developed. Some individual trees appear to be resistant to attack, particularly those that have less fluted bark. Removal of galls before the wasps emerge may be useful controls on smaller trees.

Insecticide applications, if attempted, may give best control when applied during the period of adult emergence, to prevent subsequent egg laying. This occurs in late October or early November. Soil injections of Merit or Orthene and spring foliar applications have not been effective in CSU trials.

Natural enemies, such as parasitic wasps, are common and can be important in control. Since these wasps emerge in spring, removing galls during winter and spring, after the gall wasps have emerged, will have the adverse effect of destroying natural enemies, while not affecting the gall wasp. Emerging parasites produce a smaller emergence hole than do the gall wasps. Bird predation is also common, particularly in Fall.

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