Juglans
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Aceria cinereae
butternut erineum mite
Aceria cinereae, the butternut erineum mite, is an eriophyid mite in the family Eriophyidae. Eriophyid mites are worm-like, four-legged plant parasites that are among the smallest arthropods, with some species measuring less than 0.1 mm. The genus Aceria contains many species that specialize on specific host plants, often causing distinctive growth abnormalities. A. cinereae has been observed 457 times according to iNaturalist records.
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.
Acrobasis caryivorella
pecan nursery casemaker
Acrobasis caryivorella, known as the pecan nursery casemaker, is a snout moth in the family Pyralidae described by Ragonot in 1887. It is a pest of pecan and walnut trees, with larvae that bore into new growth and developing nuts. The species has two to four generations per year and overwinters in the larval stage. It occurs in southeastern Ontario, Canada, and the eastern United States.
Catocala californica
Western Underwing Moth
Catocala californica is a moth in the family Erebidae, first described by William Henry Edwards in 1864. It belongs to the underwing moth genus Catocala, characterized by cryptic forewings that conceal brightly colored hindwings when at rest. The species is found in western North America from British Columbia and Alberta south to California. Adults are active during summer months, with larvae feeding on specific host plants.
Catocala serena
Serene Underwing
Catocala serena, the serene underwing, is a moth in the family Erebidae. It is found in eastern North America from southern Ontario and New England south to Tennessee, and west to Illinois and eastern Wisconsin. Adults are active from July to September with one generation per year. The larvae feed on shagbark hickory (Carya ovata) and black walnut (Juglans nigra).
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
Coptodisca is a genus of small moths in the family Heliozelidae, established by Walsingham in 1895. Species are leafminers whose larvae feed internally on leaves of woody plants, creating distinctive blotch mines. Several species have become invasive pests in Europe, particularly C. lucifluella and C. juglandiella on walnut (Juglans) and related trees. The genus is native to the Nearctic region with approximately 20 described species.
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.
Corythucha juglandis
Walnut Lace Bug
Corythucha juglandis, the walnut lace bug, is a univoltine or bivoltine lace bug (Hemiptera: Tingidae) native to North America and specialized on walnut (Juglans) host plants. Adults overwinter in leaf litter and become active in April or May, synchronizing with host leaf phenology. The species aggregates on the undersides of leaflets for feeding and reproduction. Both adults and nymphs are gregarious. It has been studied in Ontario, Québec, Canada, and southern Illinois, USA, with some geographic variation in voltinism reported.
Hylocurus hirtellus
Hylocurus hirtellus is a bark beetle (Scolytinae) described by Wood & Bright in 1992. It has been documented in Middle America and North America, including British Columbia, Canada. The species is known from a new host record involving northern California black walnut (Juglans hindsii), though detailed biological information remains limited.
Panaphis juglandis
Walnut Aphid, Large Walnut Aphid
Panaphis juglandis, the large walnut aphid, is a phloem-feeding pest of walnut trees (Juglans regia). It colonizes exclusively the upper (adaxial) surface of walnut compound leaves, forming dense colonies along the main vascular veins of the outer leaflets. Native to the Old World (Central Asia and southeastern Europe), it has spread across Europe and was introduced to California in the early 20th century. The species reduces tree vigor, nut yield, and quality, and excretes honeydew that promotes sooty mold growth. It forms mutualistic relationships with ant species that tend and protect colonies from predators.
Pityophthorus juglandis
Walnut Twig Beetle
Pityophthorus juglandis is an invasive bark beetle native to the southwestern United States and Mexico that vectors the fungal pathogen Geosmithia morbida, causing thousand cankers disease in walnut trees. The beetle measures approximately 1.5 mm in length and is among the few Pityophthorus species associated with hardwoods. Research has focused extensively on its chemical ecology, including the male-produced aggregation pheromone 3-methyl-2-buten-1-ol and potential semiochemical repellents for management. The species exhibits strong host discrimination during flight, preferentially landing on Juglans species while avoiding most non-host hardwoods.
Stigmella longisacca
Stigmella longisacca is a pygmy moth in the family Nepticulidae, first described in 1982. It is endemic to California, where its larvae are leaf miners on Juglans species, particularly Juglans californica. The species has a wingspan of 3.2–4.4 mm and appears to have two to three generations per year.