Chrysaster

Identification to species requires examination of adult forewing pattern and male genitalia. For C. ostensackenella, leaf mine characteristics provide field diagnostic features: yellowish blotch mines on the upper leaf surface, typically beginning with a short tunnel (1.5–2 mm) before expanding to a blotch, with relatively smooth edges and position near but not strictly associated with the main vein. These mines occupy 10–30% of the leaf compound area. Mines can be distinguished from other gracillariids on Robinia by the short initial tunnel and upper surface location. C. hagicola is distinguished by genitalia and distribution (Japan).

Associated with plantings and natural stands of Fabaceae, particularly Robinia pseudoacacia. In the invaded range in Russia, found in arboreta and tree plantings including the Mountain-Taiga Station arboretum in Gornotaejnoe village, Gornotaejnoe village plantings, and Khorol village area in Primorsky Krai. Habitat suitability is determined by host plant presence rather than specific environmental conditions.

The genus has a disjunct distribution corresponding to its two species. C. hagicola occurs in Japan. C. ostensackenella is native to North America (USA and Canada) and has been introduced to East Asia (China first recorded 2015, South Korea 2017, Japan 2021), Europe (Italy 2022), and Russia (Primorsky Krai 2022). Further spread is expected in regions with widespread Robinia pseudoacacia plantings.

In Primorsky Krai, adults observed in July. Possibly two generations per year in this region, though this remains uncertain based on available observations. In China, up to four generations may occur depending on climate conditions.

Specialized leaf-mining on Fabaceae. C. ostensackenella feeds on Robinia pseudoacacia leaves, with larvae mining between leaf surfaces. C. hagicola host associations are not documented in the provided sources.

• Robinia pseudoacacia - hostconfirmed for C. ostensackenella

Eggs are laid near the main vein or between main and secondary veins. Larvae create mines beginning as short tunnels (1.5–2 mm) that widen into blotches. Late instar larvae create semicircular cuts in the upper epidermis to exit the mine. Pupation occurs in a white, tough cocoon: on the lower leaf surface along secondary veins in the Russian Far East, but inside the mine in North America. Under laboratory conditions (24°C, 45% humidity), pupal development takes up to six days.

Adult dispersal occurs via wind currents as aerial plankton and through human-mediated transport. Immature stages can be transported with host plants for planting. Pupation location differs between geographic ranges: outside the mine in the Russian Far East versus inside the mine in North America. Each leaf mine contains a single larva.

C. ostensackenella functions as a foliar pest in invaded ranges, causing leaf discoloration, browning, drying, and premature leaf fall on Robinia pseudoacacia. The species is considered an invasive pest threatening ornamental and planted black locust stands. No information is available for ecological roles of C. hagicola in its native range.

C. ostensackenella is an emerging invasive pest of economic and ornamental concern due to damage to Robinia pseudoacacia, a widely planted tree for timber, erosion control, and ornamental purposes. The species has spread through international plant trade and natural dispersal, with potential for further introduction to the Southern Hemisphere where black locust has been established. No human relevance is documented for C. hagicola.

• Other Gracillariidae on RobiniaLeaf mines of C. ostensackenella can be distinguished by the short initial tunnel, upper surface location, relatively smooth edges, and position near but not strictly on the main vein; other species may have different mine morphologies or pupation behaviors.
• Macrosaccus robiniellaAnother invasive gracillariid on Robinia pseudoacacia; distinguished by mine characteristics and pupation location.

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• First Discovery of the North American Leaf-Mining Moth Chrysaster ostensackenella (Lepidoptera: Gracillariidae) in Russia: The Genetic Diversity of a Novel Pest in Invaded vs. Native Range