Leafy spurge stem borer

Biocontrol Agent Factsheet

The Leafy Spurge Stem Borer is a species of beetle that feeds on leafy spurge, an invasive weed.

Overview

Pests Targeted: Leafy spurge
Pest Stage: Upper portion of the stem in mid-summer; root crowns
Commercially Available? No
Scientific Name: Oberea erythrocephala
Biocontrol Agent Type: Weed-feeder

White larvae inside a woody crown of a plant. — Leafy spurge stem borer larva feeding on the inside of a leafy spurge root crown. Photo credit: USDA-APHIS-PPQ.

Common Names

Leafy Spurge Stem Borer
Red-headed leafy spurge stem borer

Relative effectiveness

Generally, leafy spurge stem borers are not considered effective because the population never gets high enough for the feeding damage to reduce an established leafy spurge stand.

Where to use

Pasture or rangeland

Leafy spurge stem borer generally do best in open sunny areas and along streams.

About Leafy Spurge Stem Borer

Leafy spurge stem borer (Oberea erythrocephala) were one of the first biocontrol agents introduced in 1980 to control leafy spurge. The stem boring larvae (immature insects) feed on the inside of leafy spurge stems and root crowns, killing the plant to just below the soil level. Adult females girdle the stem to release latex within the plant and then bore a hole in the stem. The female lays eggs above the girdled area inside the stem. A single egg is laid per hole and larvae hatch in 7 to 10 days. The larvae overwinter in the root crowns and emerge in mid-summer of the following year.

This insect is an ideal choice in wet areas where Aphthona (flea beetles) do not survive. However, even though the insect has established and can be found in many locations, the population has never become high enough to be an effective biological control agent.

Native/Non-native: Non-native
Preferred climate: temperate, cold tolerant
Region: Northern Great Plains and Rocky Mountain regions of the western US and Canada.
Established: Yes
Where established: The insect has established in low numbers in most places leafy spurge is found.

Leafy Spurge Stem Borer Appearance

Adults are narrow, slender beetles with a red head and black eyes. The hind wings are dark gray to black. One of the most notable features is the antennae which are nearly as long as the body. Adults are usually about half an inch (10-12 mm) in length.

Red headed beetle with gray body and very long antennae perched on a green leaf.

Adult leafy spurge stem borer with red head, dark body, and long antennae.

Leafy spurge stem borer larva feeding on the inside of a leafy spurge root crown.

Close-up of white latex leaking from wounds on a leafy spurge stem.

Leafy spurge stems girdled by leafy spurge stem borer adult to release latex from the plant. The female will bore a hole in the plant stem above the girdled area and lay one egg per hole.

Life Cycle

Approximate length of each portion of the life cycle for Oberea erythrocephala. Blue bars represent the overwintering stage.

Lines indicating the approximate time of year leafy spurge stem borer eggs (June to August), larvae (July to May, but overwintering mid-September through March), pupae (May to early June), and adults (late May through August) occur. — Life cycle of Oberea erythrocephala. Blue bars represent overwintering stage. Adapted from “Biology and biological control of leafy spurge” US Forest Service publication FHTET-2005-07, July 2006

How to Use Leafy Spurge Stem Borer

Biocontrol category: Classical

When to use: Leafy spurge stem borer are usually most prevalent in early July, depending on the elevation and season. Adults are best collected by hand since they often fly away to avoid sweep nets.

Rate: At least 50 or more adults should be released in a new area for establishment, but it is often difficult to collect that many at one time.

Maximizing effectiveness: This insect is secondary to the Aphthona spp. flea beetles for leafy spurge control and should not be considered as a primary control method.

Pest stage: Adults feed on the upper portion of the leafy spurge stem in mid-summer generally after flowering and seed-set. Root crowns are damaged by larvae which spend the winter in that part of the plant.

Mode of action: Weed-feeder

Compatibility: Leafy spurge stem borer is often used in conjunction with sheep and goat grazing. Herbicides should not be applied in areas with leafy spurge stem borer because the larvae feed on the stems and overwinter in leafy spurge root crowns. Herbicides would kill the top growth and thus the food source of the larvae. (Any time you use a pesticide, you must read and follow the label directions and comply with all applicable laws and regulations related to pesticide use. Also be sure that any pesticide used is approved for use in your country and state/province.)

Commercially available: No

About Leafy Spurge

Leafy spurge is a long-lived perennial weed that spreads by both root and seed. The weed invades rangeland, wildlands, roadsides and cropland. The plant grows 2 to 3 feet tall, has linear shaped blue-green leaves, and contains a white milky latex throughout the top growth. Leafy spurge produces a flat top cluster of yellow bracts that surround the inconspicuous true flower.

Leafy spurge Damage

Leafy spurge replaces other plants (including native species) resulting in negative impacts on many species within the ecosystem. The presence of leafy spurge in pastures or rangelands also reduces the suitability of land for grazing domesticated animals like cattle and horses. They avoid eating the plants because the latex they produce contains a toxic compound.

Leafy spurge top growth wilts and dies above the stem that was girdled by leafy spurge stem borer.

Plant with narrow leaves and small yellow flowers.

Leafy spurge in flowering growth stage.

Leafy spurge can become a near monoculture in the pastures and rangeland of the Northern Great Plains.

More information

Consult the following extension publications for more detailed information concerning biological control of leafy spurge.

Identification and Control of Invasive and Troublesome Weeds in North Dakota (W1411)
“Biology and biological control of leafy spurge (pdf)” US Forest Service publication FHTET-2005-07, July 2006

Author

Rodney G. Lym
Professor emeritus, North Dakota State University

Date: December 2021

Photos and Illustrations

Adult leafy spurge stem borer. Photo: USDA-APHIS-PPQ.
Leafy spurge stem borer larva feeding on the inside of a leafy spurge root crown. Photo: USDA-APHIS-PPQ.
Leafy spurge stems girdled by leafy spurge stem borer adult. Photo: USDA-APHIS-PPQ.
Leafy spurge in flowering growth stage. Photo credit: John M. Randall, The Nature Conservancy, Bugwood.org
Leafy spurge monoculture. Photo: Rodney G. Lym
Wilted Leafy spurge top growth. Phot: USDA-APHIS-PPQ.
“Biology and biological control of leafy spurge” US Forest Service publication FHTET-2005-07, July 2006