Acleris gloveranus

Status

NATIVE

DOMESTIC SURVEY

Taxonomy

Acleris gloveranus (Walsingham) (Tortricidae: Tortricinae: Tortricini)

Common names: western blackheaded budworm

Synonyms: gloverana (Lophoderus)

Adult Recognition

FWL: 8.0–10.5 mm

Forewing pattern is variable; Powell (1962d)Powell (1962d):
Powell, J. A. 1962d. Taxonomic studies on the Acleris gloverana-variana complex, the black-headed budworms (Lepidoptera: Tortricidae). Canadian Entomologist. 94: 833-840. describes eight different forms. The most common forms are illustrated here. Most forms are similar to forms of Acleris variana. Males lack a forewing costal fold.

Male genitalia are characterized by a moderately developed uncus (often hidden behind tegumen); large, lobe-like socii; elongate, rectangular valvae with well-developed sacculus and ventrally pointed apical process. Female genitalia characterized by sterigma with large, triangular anterolateral lobes; cestum absent in ductus bursae; signum absent in corpus bursae

Larval Morphology

No detailed descriptions of larval chaetotaxy are available for Acleris gloveranus owing to its historic confusion with A. variana. The following account is based primarily on photos of larvae of A. gloveranus in western North America. Larval chaetotaxy probably closely mirrors that of A. variana.

Larvae are approximately 11–15 mm in length and are green with a black head that turns brown in the final instar. The prothoracic shield is green to brown and heavily shaded with black on the posterolateral margins. If similar to A. variana, an anal comb may be present with 6–10 teeth.

Similar Species

Acleris gloveranus is nearly identical to A. variana in both biology and morphology. In most places, they can be separated by distribution: A. gloveranus occurs in western North America and A. variana occurs in eastern North America. However, they meet in the Canadian Rockies and may be extremely difficult to separate there. Powell (1962b)Powell (1962b):
Powell, J.A. 1962b. Biological and taxonomic notes on two California species of Proteoteras (Lepidoptera: Tortricidae). Pan-Pacific Entomologist 38: 191- 195. outlined minor genitalic differences that can be used to separate the two species. In males, the sacculus is broader and less elongate in A. gloveranus, while it is narrower and more elongate in A. variana. In A. gloveranus females, the sterigma is broad, with lobes connected, and a cestum is absent. In A. variana females, the sterigma is narrow with the lobes separate, and a weakly sclerotized cestum is present. In addition, females of A. variana have large abdominal scale tufts that are used to cover the eggs; these are lacking in A. gloveranus females.

Distribution

Acleris gloveranus occurs from Alaska and northwestern Canada south to northern California and western Montana.

Biology

The following account is summarized from EPPO (1997)EPPO (1997):
EPPO (European and Mediterranean Plant Protection Organization). 1997. Data sheets on quarantine pests: Acleris variana and Acleris gloverana . https://gd.eppo.int/download/doc/797_ds_ACLRSP_en.pdf [accessed 15 October 2020] (.pdf). and Otvos et al. (2002)Otvos et al. (2002):
Otvos, I. S., Conder, N., Heppner, D. G. 2002. Acleris gloverana (Walshingham), Western Blackheaded Budworm (Lepidoptera: Tortricidae), pp. 28-31. In : Mason, P. G., Huber, J. T. (eds.). Biological Control Programmes in Canada, 1981-2000. CABI Publishing. New York, New York. 583 pp..

Acleris gloveranus completes one generation per year. Adults are present in late July through September. Females lay single eggs on the underside of needles in the upper regions of host trees. Eggs overwinter until the following spring, and larvae hatch starting in mid May. First instars feed inside opening buds, mid-instars web together needles to create a nest, and last instars are free-feeding. Males and 50% of females complete four larval instars while the remaining females complete five instars. Pupation occurs in webbed needles. Adults eclose in approximately two weeks.

This species can be a serious forest pest, and severe outbreaks can cover millions of acres. In coastal forests, extensive defoliation by A. gloveranus can result in up to 50% tree mortality. Outbreaks tend to occur after periods of low rainfall.

Acleris gloveranus feeds on a variety of fir (Abies spp.), hemlock (Tsuga spp.), larch (Larix sp.), and spruce (Picea spp.).

Plant Associations

View full screen host table here

Links

Additional photos and distribution map in North America available at Moth Photographers Group.