Eucosma giganteana

Distinguished from congeners by its larger size (wingspan 34–38 mm versus smaller Eucosma species) and association with Silphium host plants. Field identification relies on host plant presence and timing of adult flight in summer. Attraction to (E)-8-dodecenyl acetate in pheromone traps may assist detection.

Adults have a wingspan of 34–38 mm. As a tortricid moth, it has the characteristic bell-shaped wing posture at rest. Specific coloration and pattern details are not documented in available sources.

Native North American prairie ecosystems; silflower crop fields; agroecosystems with Silphium integrifolium breeding plots. Field sites in Kansas included perennial grasses in inter-rows, surrounded by hardwood windbreaks, intermediate wheat grass, perennial sorghum, and fescue blends.

Widespread in the United States from North Carolina south to Florida, west to Minnesota and Texas, with additional records from Pennsylvania, North Dakota, and New Mexico. Native range coincides with native prairies of Silphium species.

Adults are on wing in January and from April to September across the range. In Kansas silflower fields, adult flight occurs primarily June–August, with peak activity in early to mid-summer. Lower activity threshold is 17°C.

Specialist herbivore feeding exclusively on Silphium species. Larvae feed on flower heads (capitula) of Silphium integrifolium and Silphium perfoliatum, then descend to feed on root crowns.

• Silphium integrifolium - primary hostsilflower; novel perennial oilseed crop
• Silphium perfoliatum - primary hostcup plant

Univoltine annual cycle. Adults emerge in summer (June–July), mate, and oviposit on flower heads. Neonate larvae burrow into flower heads and feed until late summer. Larvae then descend to root crowns in autumn, burrow in, feed, and overwinter as larvae. Pupation occurs the following spring, with adult emergence the following summer.

Adults exhibit significant attraction to (E)-8-dodecenyl acetate, a potential pheromone component. Flight mill assays show adults fly an average of 23 km in 24 hours. Flight is diurnal with longest distances in morning (4:00–12:00), 1.8-fold greater than night flights (20:00–4:00). Attractive semiochemicals reduce flight distance by 78–80%, indicating arrestment properties. Both sexes are collected on flowers.

Native specialist herbivore of Silphium species. As a pest of domesticated silflower, reduces seed production by 45–85% in infested heads and can reach 95% flower head colonization in unmanaged fields. Subject to biological control by generalist predators and at least one braconid parasitoid species.

Major limiting factor to development and commercialization of Silphium integrifolium as a sustainable oilseed alternative. Infestation causes seed damage, flower rot, root rot, and long-term plant degradation. Target for semiochemical-based monitoring and management strategies; growing degree day model developed to guide integrated pest management timing.

• Other Eucosma speciesSmaller body size; different host associations; (E)-8-dodecenyl acetate attraction may be species-specific
• Generalist tortricid mothsE. giganteana is Silphium-specific; generalists lack this strict host association

• pest
• specialist herbivore
• silflower
• pheromone
• flight capacity
• native range
• prairie
• oilseed crop
• integrated pest management

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Field Trapping and Flight Capacity of Eucosma giganteana (Riley) (Lepidoptera: Tortricidae) in Response to Behaviorally Active Congeneric Semiochemicals in Novel Silflower Agroecosystems
• Developing a growing degree day model to guide integrated pest management of Eucosma giganteana, a pest of a novel perennial oilseed crop
• Assessing effective mechanical and chemical strategies for managing Eucosma giganteana (Lepidoptera: Tortricidae) in the perennial oilseed crop, Silphium integrifolium (Asteraceae: Heliantheae).