Argyrotaenia franciscana

Status

NATIVE

PORT INTERCEPT | DOMESTIC SURVEY

Taxonomy

Argyrotaenia franciscana (Walsingham) (Tortricidae: Tortricinae: Archipini)

Common names: orange tortrix, apple skinworm

Synonyms: citrana (Tortrix), kearfotti (Argyrotaenia)

Note: Argyrotaenia franciscana and A. citrana are considered separate species in much of the economic literature. Landry et al. (1999)Landry et al. (1999):
Landry, B., Powell, J. A., Sperling, F. A. H. 1999. Systematics of the Argyrotaenia franciscana (Lepidoptera: Tortricidae) species group: evidence from mitochondrial DNA. Annals of the Entomological Society of America. 92: 40-46. concluded that they form a single species based on molecular data.

Subspecies: A. franciscana insulana (Anacapa Island, California)

Adult Recognition

FWL: 6.0–10.0 mm

In California, Argyrotaenia franciscana has two common phenotypes that were previously separated into two species. One form (formerly A. citrana) has broad, orange to orange-brown forewings with a well-defined dark median fascia and outer spot on the costa, and the hindwings are white to gray. The other form (typical A. franciscana) has narrow, gray to brownish-gray forewings with a dark, variably defined median fascia and an outer spot on the costa, and the hindwings are primarily gray. Wing pattern and size can be quite variable although most individuals show remnants of a median fascia and outer costal spot. Males lack a forewing costal fold.

Male genitalia are characterized by a moderate, parallel-sided, finger-like uncus; reduced socii; and large, subtriangular valvae with a well-developed sacculus. Female genitalia are characterized by a ductus bursae with a sclerotized plate near the ostium and a large, hook-shaped signum in the corpus bursae.

Larval Morphology

The following account is summarized from MacKay (1962a)MacKay (1962a):
MacKay, M. R. 1962a. Larvae of the North American Tortricinae (Lepidoptera: Tortricidae). Canadian Entomologist, Supplement 28: 1-182..

Mature larva 13–15 mm in length; width of head approximately 1.1–1.3 mm; head, prothoracic shield light brown to brownish yellow, unmarked; legs brown; body color varies with host plant, but usually pale to dark green; anal shield concolorous with body; anal fork well-developed; SV group on A1, 2, 7, 8, 9 numbering 3:3:3:2:2.

Detailed figures of larval chaetotaxy are available in MacKay (1962a)MacKay (1962a):
MacKay, M. R. 1962a. Larvae of the North American Tortricinae (Lepidoptera: Tortricidae). Canadian Entomologist, Supplement 28: 1-182..

Similar Species

Adults most closely resemble some forms of Epiphyas postvittana. Males of Argyrotaenia franciscana can be distinguished by the lack of a costal fold. The genitalia of both sexes are distinct. Choristoneura rosaceana males have been captured in A. franciscana pheremone traps; however, adults of these two species are unlikely to be confused.

Larval damage by Pandemis pyrusana may resemble that of A. franciscana and the larvae are similar in appearance. Argyrotaenia franciscana larvae are similar to those of many other Archipini that have a brown, unmarked head and prothoracic shield.

Distribution

Argyrotaenia franciscana is found along the west coast of North America, from Baja California north to British Columbia.

Biology

The following account is summarized from Powell (1964b)Powell (1964b):
Powell, J. A. 1964b. Biological and taxonomic studies on tortricine moths, with reference to the species in California. University of California Publications in Entomology. Vol. 32. 317 pp..

Argyrotaenia franciscana is bivoltine or multivoltine, depending on location. In warmer inland areas of California, larvae aestivate during the summer and only two generations are completed. In cooler coastal areas there may be up to 5 continuous overlapping generations with adults present year-round.

Eggs are laid on smooth surfaces of leaves, fruits, and twigs in masses that contain approximately 200 individual eggs. Early instar larvae skeletonize leaves under a silk shelter; later instars roll, fold, or web leaves together or to fruits. Larvae complete 5-7 instars in a period of 20–30 days. Larvae or pupae overwinter in dead leaves, in mummified fruits, under buds, or on weedy herbaceous plants in the same vicinity as the host. Pupation occurs in the final larval shelter. Larvae can cause economic damage by directly feeding on developing fruit in citrus (Citrus spp.), apple (Malus spp.), and grape (Vitis spp.). Larvae may also feed on stems, causing fruit to drop.

Argyrotaenia franciscana has been described as one of the most polyphagous tortricid species in North America. Its host list includes plants in more than 40 families, many of which are important crops.

Plant Associations

View full screen host table here

Links

Additional photos and a distribution map of this species in North America are available at Moth Photographers Group.