Moths of North Carolina
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Ostrinia Members:
4 NC Records

Ostrinia obumbratalis (Lederer, 1863) - Smartweed Borer Moth

Superfamily: Pyraloidea Family: CrambidaeSubfamily: PyraustinaeTribe: PyraustiniP3 Number: 801421.00 MONA Number: 4947.00
Comments: This genus was recently revised by Yang et al. (2021), with fifteen species now described worldwide. Four species occur in North America and all occur in North Carolina. As described by Yang et al. (2021), Ostrinia obumbratalis is included in their Clade I, the Obumbratalis Species Group. In North Carolina, this group also includes O. multispinosus, a closely related species that was described by Yang et al. (2021).
Species Status:
Field Guide Descriptions: Online Photographs: MPG, BugGuide, iNaturalist, Google, BAMONA, GBIF, BOLDTechnical Description, Adults: Munroe (1976)Technical Description, Immature Stages: Heinrich (1919)                                                                                 
Adult Markings: Ostrinia obumbratalis is similar in size and appearance to O. penitalis, but with a paler yellow or off-white ground color and brownish rather than reddish lines and shadings. Both the antemedian and postmedian lines are dentate. The postmedial line extends inward from the inner margin a short distance before bluntly projecting outwards as a large tooth that is often bifid. It then projecting inward to form a V-shaped notch. From there, it continues to the costa as an outwardly bowed line with smaller teeth. The subterminal line consists of a diffuse dentate or zig-zag line that is sometimes reduced to a diffuse shaded region. The reniform is represented as a dark line or bar that runs nearly perpendicular to the costa; it is often followed by faint dark shading. The hindwing is about the same shade as the forewing and has an even but dentate postmedial line that runs fairly straight across the wing, at least as far as the cell. A similarly even, dentate subterminal line is also present. The short discal bar or spot in the middle of the wing that is present in O. penitalis is missing (Scholtens, 2017).

According to Yang et al. (2021), O. multispinosa is very similar to O. obumbratalis in external appearance, but the forewing transverse markings and dentate subterminal band in the former are somewhat less defined. Specimens are often worn, and genitalia or barcoding may be required in many instances for a positive identification.
Wingspan: 20-27 mm (Heinrich, 1919).
Adult Structural Features: Heinrich (1919) has illustrations of the male and female genitalia.
Adult ID Requirements: Identifiable from photos showing hindwings, abdomen, or other specialized views [e.g., frons, palps, antennae, undersides].
Immatures and Development: The following life history account is from Schopp (1931) in Kansas. Females lay clusters of 6-21 eggs on the host plant that typically hatch within 5-14 days. The eggs are usually laid on a smartweed leaf near the top of the plant. The hatchlings bore into the stem close to the stem tip and feed communally. The young larvae feed together in their burrow until about the second instar when the tip becomes badly wilted. They then exit the communal burrow and make individual burrows in the internodes lower on the stems.

An older larva enters a stem by cutting a circular hole just above a node. As it feeds on the internal tissues, frass is deposited outside of the hole where it often hangs by webbing in a loose cluster. When the food is exhausted, the larva moves to another node and make another burrow. Pupation occurs within the stem where the prepupa constructs a series of silk sheets partly across the burrow. It also constructs a thicker silk webbing at the rear of the larva that separates it from a frass plug. The pupal stage lasts about a month, and there are more than one brood per year. Poos (1927) reported that the full-grown larvae of the last brood in Ohio overwinter in burrows in the host plant (Persicaria) and pupate in the spring. During the spring they also pupate in shelter plants near the host plant. In Ohio, the areas of a burrow before and after the pupa are plugged with particles of pith that is webbed with silk. The larvae are indistinguishable from those of O. nubilalis based on external coloration and patterning, and require detailed examination of the setae on the head to sort the two apart (Heinrich, 1919).
Larvae ID Requirements: Identifiable from close inspection of specimens or by DNA analysis.
Distribution in North Carolina
Distribution: Ostrinia obumbratalis is broadly distributed across eastern North America, including southern Canada where it has been documented in Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, and Prince Edward Island. In the U.S., it occurs from Maine and New Hampshire southern to southern Florida, and westward to central Texas, Oklahoma, Kansas, Illinois and Wisconsin. As of 2023, our very limited records are from the Piedmont and northern Blue Ridge.
County Map: Clicking on a county returns the records for the species in that county.
Flight Dates:
 High Mountains (HM) ‚Č• 4,000 ft.
 Low Mountains (LM) < 4,000 ft.
 Piedmont (Pd)
 Coastal Plain (CP)

Click on graph to enlarge
Flight Comments: The adults have been observed from February through September in different areas of the range, with peak activity from May through September. As of 2023, we have only one dated record that is from late May.
Habitats and Life History
Habitats: We have one record from along the New River but with the exact habitat unrecorded. All of the rest of our records are historic (Brimley, 1938).
Larval Host Plants: The larvae are polyphagous and feed on several families of herbaceous plants, including members of the the Asteraceae, Poaceae, Polygonaceae and Rosaceae (Poos, 1926; Schopp, 1931; Munroe, 1976; Godfrey et al., 1987; Solis, 2008; Robinson et al., 2010; Beadle and Leckie, 2018). Some use is made of corn, but this species is considered to be only a minor pest of that crop. Smartweeds (Persicaria spp.) are the primary hosts, but other species are occasionally used that are often in close proximity to smartweeds. The reported genera and species that are used include Giant Ragweed (Ambrosia trifida), thoroughworts (Eupatorium), Common Morning Glory (Ipomoea purpurea), Common Apple (Malus domestica), Pale Smartweed (Persicaria lapathifolia), Spotted Lady's-thumb (P. maculosa), Pennsylvania Smartweed (P. pensylvanica) and cockleburs (Xanthium). - View
Observation Methods: The adults are attracted to lights.
Status in North Carolina
Natural Heritage Program Status:
Natural Heritage Program Ranks: GNR [S1S3]
State Protection: Has no legal protection, although permits are required to collect it on state parks and other public lands.
Comments: As of 2023 we have only one recent record, with all others being historical.

 Photo Gallery for Ostrinia obumbratalis - Smartweed Borer Moth

Photos: 1

Recorded by: Doug Blatny / Jackie Nelson on 2011-05-28
Ashe Co.