Walnut-pest
Guides
Aceria brachytarsus
pouch gall mite, walnut purse gall mite
Aceria brachytarsus is an eriophyoid mite species that induces leaf-pouch galls on walnut trees (Juglans spp.). Formerly classified as Eriophyes brachytarsus, this microscopic arachnid is known for producing distinctive bladder-like galls on foliage. The species has been documented in California, Iran, Spain, and Belgium.
Aceria caulis
Black Walnut Petiole Gall Mite
Aceria caulis, the Black Walnut Petiole Gall Mite, is an eriophyid mite in the superfamily Eriophyoidea. Like other members of its genus, this species is a plant parasite that induces abnormal plant growth. The specific epithet 'caulis' and common name suggest association with walnut petioles, though detailed biological studies of this particular species appear limited in the available literature.
Aceria erinea
Walnut Blister Mite
Aceria erinea is a gall-forming eriophyid mite that induces characteristic blister-like galls on the leaves of common walnut (Juglans regia). First described by Alfred Nalepa in 1891, this microscopic arachnid is a specialized plant parasite with a highly restricted host range. The mite's feeding activity causes distinctive erineum galls—fuzzy, felt-like patches on leaf surfaces. Like other eriophyid mites, it has a worm-like body with only four legs and undergoes rapid development, completing its life cycle in approximately one to two weeks under favorable conditions.
Conotrachelus juglandis
butternut curculio
Conotrachelus juglandis, the butternut curculio, is a true weevil in the family Curculionidae. It is associated with walnut species (Juglans), where it injures shoots and nuts. The species was first described in 1876 and occurs across eastern North America, from New England through southern Canada to the Great Plains, and south to Kansas, Alabama, and Georgia. Life history studies have been conducted in Connecticut (1912), West Virginia (1922), and Michigan (1979).
Coptodisca juglandiella
Walnut Shield-bearer
Coptodisca juglandiella is a Nearctic leafminer moth in the family Heliozelidae, first described by Chambers in 1874. Native to North America, it was discovered in Hungary in 2019 as a new invasive species for Europe. The larvae feed internally on walnut leaves, creating distinctive blotch mines. Unlike its congener C. lucifluella, it has not undergone a host plant shift since introduction to Europe.
Coptodisca lucifluella
walnut shield bearer
Coptodisca lucifluella is a small leaf-mining moth in the family Heliozelidae, native to eastern North America and invasive in Europe since 2010. Larvae create distinctive blotch-shaped mines on walnut and hickory foliage, then construct oval silk-attached cases for pupation. The species has undergone a documented host shift in Europe, expanding from its native specialization on Carya (pecan) to primarily exploiting Juglans regia (common walnut) and occasionally other Juglandaceae. It completes 3–4 generations annually in Italy, with autumn generations producing substantially more mines than spring generations.
Datana integerrima
Walnut Caterpillar Moth
Datana integerrima, commonly known as the walnut caterpillar moth, is a North American species in the family Notodontidae. The adult moths have a wingspan of 35–50 mm and are active from May to August. The larvae are notable defoliators of walnut, hickory, and other hardwood trees, feeding gregariously in large groups. While capable of causing significant defoliation, single-season outbreaks rarely cause lasting damage to healthy trees.
Megaxyela major
Megaxyela major is a species of sawfly in the family Xyelidae, one of the most primitive families of Hymenoptera. The genus Megaxyela contains some of the largest xyelid sawflies. Species in this genus are associated with walnut (Juglans) and hickory (Carya) trees as hosts for their larvae.
Nolidae
Tufted Moths, Tuft Moths
Nolidae is a family of small to medium-sized moths within the superfamily Noctuoidea, comprising approximately 1,400-1,700 described species worldwide. Members are characterized by relatively dull coloration and, in the subfamilies Nolinae and Collomeninae, distinctive tufts of raised scales on the forewings. The family was historically treated as a subfamily of Noctuidae but is now recognized as distinct based on morphological and molecular evidence. A defining feature of the family is the construction of a silk cocoon with a vertical exit slit for pupal emergence.
Panaphis
Panaphis is a genus of aphids in the family Aphididae, subfamily Calaphidinae. The best-known species, Panaphis juglandis, is a destructive pest of walnut trees (Juglans spp.) and forms mutualistic associations with tending ants. Ants protect these aphids from predators such as lady beetles in exchange for honeydew. The genus has been documented in parts of Europe including Denmark, Norway, and Sweden.
Pityophthorus
Pityophthorus is a large genus of bark beetles in the family Curculionidae, containing more than 540 described species. The genus is characterized by its association with coniferous and hardwood host trees, with species distributed across North America, Europe, and other regions. Some species, such as P. juglandis (the walnut twig beetle), are significant forest pests that vector pathogenic fungi causing tree diseases.
Rhagoletis juglandis
walnut husk fly, black walnut fly
Rhagoletis juglandis is a univoltine tephritid fruit fly that infests walnut husks, primarily in the southwestern United States and Mexico. Adults emerge in mid to late summer and feed on dew and plant sap. Females deposit eggs in batches beneath the husk surface of developing walnuts; larvae tunnel into the inner husk and feed for 3–5 weeks before pupating in soil. The species exhibits distinctive courtship behavior including male low-frequency wing vibration with infrasound, and engages in superparasitism—reusing infested hosts even when uninfested fruits are available. It is a pest of cultivated walnuts and has been introduced to Europe.