Phthorimaea operculella

Name

Phthorimaea operculella (Zeller, 1873)

Common names: potato tuber moth, potato tuberworm; tobacco splitworm

Original combination: Gelechia operculella Zeller, 1873

Synonyms:

• Gelechia terrella Walker, 1864
• Bryotropha solanella Boisduval, 1874
• Gelechia tabacella Ragonot, 1879
• Gelechia sedata Butler, 1880
• Phthorimaea argentinae Povolný, 1989
• Gelechia piscipellis Howard, 1897, (nec Zeller, 1873), misidentification
• Phthorimaea epicentra auctt., (nec Meyrick, 1909), misidentification

Classification: Gelechioidea: Gelechiidae: Gelechiinae: Gnorimoschemini

Adult recognition

Adults are about 5.5⁠–⁠7.2 mm in forewing length. They are variably light brown and gray. The forewing foldFold:
The invisible line of folding below the discal cell on the forewing.
has light yellow scales between grayish-black spots, and the apical area has many white-based black scales. The labial palpusLabial palpus:
The more prominent, elongate pair of appendages on the head, usually three-segmented (pl. palpi).
is upturned. The hindwing is gray, trapezoidal, and modified with a hair-pencil from the base of the costaCosta:
(1) The anterior margin of the wing. (2) In the male genitalia, the dorsal margin of the valva.
in males. The abdomen is gray with two lateral hair-pencils near the apex in males. The male genitalia have an oval gnathosGnathos:
A variously shaped bridge-like structure, usually hooked or bowed, crossing the tegumen below the uncus.
, and the valvaValva:
One of the pair of large lateral appendages of the male genitalia (pl. valvae).
has a dilated, curved apex. Females have segment eight with a distinct transverse zone of foam-like texture in the medial part of the sternum, a broadly funnel-shaped antrumAntrum:
Posterior section of the ductus bursae, posterior of the colliculum.
leading into a very short ductus bursaeDuctus bursae:
The usually narrow duct between the ostium and antrum and the corpus bursae.
, and a small sickle-shaped signumSignum:
Any sclerite, sclerotized area, or discrete granular area on the wall of the corpus bursae (pl. signa).
.

Immature stages

The prothoracic shieldProthoracic shield:
Also called the T1 shield. In the larva, the extensive sclerotized area of the dorsal half of the prothorax. It bears six setae on each side, and its color pattern is often diagnostic.
of P. operculella lacks a dark band on the posterior margin and the abdominal SD pinaculumPinaculum:
In the larva, a raised, blister-like area that is often but not necessarily pigmented. They normally surround a seta, or if more than one seta, they are considered to be fused. Some taxa, especially internally boring larvae, may have extra pinacula without setae.
is about as large as the spiracleSpiracle:
Respiratory openings, mainly of interest for larval chaetotaxy. One pair on most segments.
of the corresponding segment. In addition, the line joining setae L1 and S2 runs posterior to stemma one, all thoracic legs are pigmented, SD1 on A9 is hairlike, and the three L setae of A9 are in a triangular arrangement.

PDF - Dichotomous key to Gelechiid larvae

Similar species

This species is superficially similar to Scrobipalpa aptatella (Walker) and S. ergasima (Meyrick), but it differs by the forewing having the light brown foldFold:
The invisible line of folding below the discal cell on the forewing.
with light yellow scales between grayish-black spots, the spots in the middle of the wing indistinct, the male uncusUncus:
The prominent projection from the dorsal tegumen of the male genitalia. May be variously shaped as a hook, knob, hood, etc.
broadly rounded, and the gnathosGnathos:
A variously shaped bridge-like structure, usually hooked or bowed, crossing the tegumen below the uncus.
not hook-shaped.

As with many Gelechioidea, no one larval character of P. operculella is totally diagnostic; this species is recognized by the combination of characters. Unlike Keiferia lycopersicella and Tuta absoluta, the prothoracic shieldProthoracic shield:
Also called the T1 shield. In the larva, the extensive sclerotized area of the dorsal half of the prothorax. It bears six setae on each side, and its color pattern is often diagnostic.
is uniformly colored. The pigmented legs of P. operculella are also unusual. The trisetose L group on A9 separates P. operculella from Symmetrischema tangolias and Tecia solanivora which have a bisetose L group on that segment.

Behavior

Eggs are laid on the hairy underside of leaves. Larvae mine leaves and stems in various solanaceous plants, but they act primarily as tuber borers in potato and as leaf miners in tobacco. When they are fully grown, larvae pupate in the soil near the base of host-plants, in leaf remains, or in some other suitably sheltered site. Pupae are enclosed in a white silken cocoon. They are multivoltine occurring about five or six generations per year.

Distribution

Native to South America, introduced worldwide. USA (widely in the United States, particularly California and southeastern states north to Maryland). Throughout the New World. New Zealand, South Africa.

Hosts

Nicotiana glauca Graham (Tree tobacco)

Nicotiana tabacum L. (Cultivated tobacco)

Solanum dulcamara L. (Climbing nightshade)

Solanum lycopersicum L. (Garden tomato)

Solanum melongena L. (Eggplant)

Solanum nigrum L. (Black nightshade)

Solanum tuberosum L. (Irish potato)

Comments

This species occurs in almost all potato production areas in the world. It also feeds on other Solanaceae including important weeds in potato fields (e.g., black nightshade, Solanum nigrum L.).

Literature

Carter 1984Carter 1984:
Carter DJ. 1984. Pest Lepidoptera of Europe with special reference to the British Isles. Series Entomologica vol. 31. W. Junk, Dordrecht / Boston / Lancaster. 431 pp.

Hilje 1994Hilje 1994:
Hilje L. 1994. Caracterizacioacute;n del dantilde;o de las polillas de la papa, Tecia solanivora y Phthorimaea operculella (Lepidoptera: Gelechiidae), en Cartago, Costa Rica. Manejo Integrado de Plagas 31: 43-46.

Huemer and Karsholt 2010Huemer and Karsholt 2010:
Huemer P and Karsholt O. 2010. Microlepidoptera of Europe. Vol. 6: Gelechiidae II (Gelechiinae: Gnorimoschemini). Apollo Books, Stenstrup.

MacKay 1972MacKay 1972:
MacKay M. 1972. Larval sketches of some microlepidoptera, chiefly North American. Memoirs of the Entomological Society of Canada 88: [1]-83.

Rondon 2010Rondon 2010:
Rondon SI. 2010. The Potato Tuberworm: a literature review of Its biology, ecology, and control. American Journal of Potato Research 87: 149&-166.

Weisman 1986Weisman 1986:
Weisman DM. 1986. Keys for the identification of some frequently intercepted lepidopterous larvae. U.S. Department of Agriculture, APHIS 81-47, 64 pp.

Zeller 1873Zeller 1873:
Zeller PC. 1873. Beitrauml;ge zur Kenntniss der nordamericanischen Nachtfalter, besonders der Microlepidopteren. Verhandlungen der Kaiserlich-Kouml;niglichen Zoologisch-Botanischen Gesellschaft in Wien 23: 201-334, Taf. III-VI.