Epiblema strenuana (Walker) (Tortricidae: Olethreutinae: Eucosmini)
Common name: ragweed borer moth
Synonyms: antaxia (Eucosma), exvagana (Grapholita), flavocellana (Steganoptycha), subversana (Grapholita)
FWL: 4.0–9.0 mm
Head and thorax gray to brown; forewing with ground color pale brown, but heavily dusted with dusty gray scales as to obscure much of the ground color; interfascial spot whitish to bronzy-gray, often barely distinguishable; ocellus prominent, white, with a black longitudinal dash; costal strigulae weakly contrasting except towards apex where they are often separated by patches of orange scales; males without costal fold; hindwing pale brown.
Male genitalia are characterized by long, finger-like socii and valvae with a broad concavity on the ventral margin of the valve between the sacculus and cucullus. Female genitalia are characterized by a rectangular and elongate sterigma; ductus bursae with a twist-like sclerotized contortion near the juncture of the ductus seminalis; and two large blade-like signa.
The following account is summarized from MacKay (1959)MacKay (1959):
MacKay, M. R. 1959. Larvae of the North American Olethreutidae (Lepidoptera). Canadian Entomologist, Supplement 10: 1-338..
Mature larvae are approximately 12–15 mm in length, width of head 1.0–1.2 mm. Head brown, occasionally with black pigmentation laterally; prothoracic shield brown; thoracic legs and anal shield brown; body pale; anal fork absent. SV groups on A1, 2, 7, 8, 9 usually 2:2:2:2:1.
A complete description of larval chaetotaxy is available in MacKay (1959)MacKay (1959):
MacKay, M. R. 1959. Larvae of the North American Olethreutidae (Lepidoptera). Canadian Entomologist, Supplement 10: 1-338..
Several species of Epiblema are very similar to E. strenuana, especially E. minutana and E. luctuosissima. Dissection is usually necessary to separate them. Males of E. minutana tend to have shorter and sometimes more triangular socii whereas the females of E. minutana tend to have a shorter, less rectangular sterigma compared to E. strenuana. Males of E. strenuana have a more constricted medial portion of the valvae compared to E. luctuosissima. Females of E. strenuana have larger signa in the corpus bursae compared to E. luctuosissima.
Epiblema strenuana is broadly distributed across North America, from Minnesota west to Colorado and New Mexico and east to Florida and Maryland. It is also known from southern California and northern Mexico. MacKay (1959)MacKay (1959):
MacKay, M. R. 1959. Larvae of the North American Olethreutidae (Lepidoptera). Canadian Entomologist, Supplement 10: 1-338. reported it from the US Virgin Islands, but these records require verification. Its range appears to overlap with several of its known host plants, but some of these records may be confused in the literature with the formerly synonymized species E. minutana (Gilligan et al. 2020aGilligan et al. 2020a:
Gilligan, T. M., Wright, D. J., Brown, R. L., Augustinus, B. A., Schaffner, U. 2020a. Taxonomic issues related to biological control prospects for the ragweed borer, Epiblema strenuana (Lepidoptera: Tortricidae). Zootaxa. 4729(3): 347-358.).
Epiblema strenuana has been released as a biological control agent in Australia (McClay 1987McClay 1987:
McClay, A. S. 1987. Observations on the biology and host specificity of Epiblema strenuana [Lepidoptera, Tortricidae], a potential biocontrol agent for Parthenium hysterophorus [Compositae]. Entomophaga. 32: 23-34., Gerber et al. 2011Gerber et al. 2011:
Gerber, E., Schaffner, U., Gassmann, A., Hinz, H. L., Seier, M., Muuml;ller-Schauml;rer, H. 2011. Prospects for biological control of Ambrosia artemisiifolia in Europe: learning from the past. Weed Research. 51: 559-573.) and China (Wan et al. 1995Wan et al. 1995:
Wan, F.‐H., Wang, R., Ding, J. 1995. Biological control of Ambrosia artemisiifolia with introduced insect agents, Zygogramma suturalis and Epiblema strenuana , in China. In : Scott, R.R. (ed.), Eighth International Symposium on Biological Control of Weeds, Canterbury, New Zealand. CSIRO, Melbourne, pp. 193-200., Ma et al. 2008Ma et al. 2008:
Ma, J., Guo, J., Wan, F. H., Hu, X. N. 2008. Biological control of Ambrosia artemisiifolia and A . trifida . In : Wan, F.H. (ed.), Biological Invasions: Biological control theory and practice. Science Press, Beijing, pp. 157-185.), but rejected as a proposed biological control agent in India (Jayanth 1987Jayanth 1987:
Jayanth, K. P. 1987. Investigations on the host-specificity of Epiblema strenuana (Walker) (Lepidoptera: Tortricidae), introduced for biological control trials against Parthenium hysterophorus in India. Journal of Biological Control. 1.2: 133-137.) and South Africa (McConnachie 2015McConnachie 2015:
McConnachie, A. J. 2015. Host range tests cast doubt on the suitability of Epiblema strenuana as a biological control agent for Parthenium hysterophorus in Africa. BioControl. 60: 715-723.).
The following account is summarized from McClay (1987)McClay (1987):
McClay, A. S. 1987. Observations on the biology and host specificity of Epiblema strenuana [Lepidoptera, Tortricidae], a potential biocontrol agent for Parthenium hysterophorus [Compositae]. Entomophaga. 32: 23-34..
Eggs are laid singly or in small groups and attached to the stems or leaves of the host plant. In Mexico, eggs hatch in approximately 4 days in early March. Newly hatched larvae will feed externally on almost any part of the plant but seems to especially prefer axillary buds and young foliage. Larvae then bore into a stem of the plant, forming a thin, elongate gall. The mature larvae will then cut a thin-walled emergence hole in the upper portion of the gall and pupate. Adults eclose and leave the exuviae extruding from the exit hole in the gall. Typically, three generations occur per year in northern Mexico, with larvae active from March to November. Overwintering occurs in the larval stage with pupation occurring in the early spring. Two generations occur per year in the midwestern United States (Gilligan et al. 2008Gilligan et al. 2008:
Gilligan, T. M., Wright, D. J., Gibson, L. D. 2008. Olethreutine moths of the midwestern United States, an identification guide. Ohio Biological Survey, Columbus, Ohio. 334 pp.).
Larvae have been reported as stem borers in annual ragweed (Ambrosia artimisiifolia), Santa Maria feverfew (Parthenium hysterophorus) and other Asteraceae. It has also been recorded feeding on Chenopodium (Amaranthaceae) and Polygonum (Polygonaceae).
View full screen host table here
Authors: KA Austin, TM Gilligan, ME Epstein
Content last updated May 2025
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