Head Clipper Weevil

Overview

The head clipper weevil, Haplorhynchites aeneus, is a pest of plants in the Asteraceae family, including sunflower (Helianthus spp.), aster (Symphotrichum spp.), and coneflower (Echinacea spp.). It is most common in prairies with large populations of prairie dock, ragweed, compass plant, and prairie asters. These weevils have exceptionally long snouts, with their mouthparts at the end. Their bodies are uniformly black, often with a bronze or copper sheet. At maturity, they can reach up to 1/4"-1/3" in length.

This insect is named for its unusual behavior in clipping flower heads off plants. Female weevils insert their mouthparts into the stem of the plant, chewing a ring of holes or a groove around the stem below the flower, partially severing it. Eventually, the flower head will fall, hanging by the remaining stem tissue before breaking off completely and falling to the ground. This insect is not otherwise damaging, posing a primarily aesthetic concern in the home.

Symptoms & Diagnosis

Bent or broken flower heads, starting about an inch down from the base of the flower. Missing and/or hanging leaves can also be noted, as they will target these when flowers are not available. 

Life Cycle

Head clipper weevils produce only one generation per year. Female weevils partially sever the heads of flowers by chewing a ring around the peduncle after laying their eggs in the flower disk. Once the injured flower heads fall, the larvae emerge and consume the ovules of the fallen flower. Mature larvae leave the flower head and crawl into the soil, where they overwinter. Pupation begins in spring and into early summer, reaching their adult stage by mid-summer, usually at the end of June through the beginning of August.  

Adults remain active for 2-3 weeks in mid-summer. Because adult head clipper weevil damage is primarily aesthetic, control is not necessary in a home garden setting.  

Integrated Pest Management Strategies

1. Monitor. Look for signs of weevil damage, including damaged or declining flower heads, bent or nodding flowers or leaves, and missing or fallen flowers. During mating, they tend to congregate on the face of the flower and are easily seen.  

2. Remove damaged flower heads. Prune off broken or damaged flower heads and collect any fallen flowers. Dispose of clippings as they contain the weevil eggs and/or larvae. Destroy the flowers or throw them away.  

3. Chemical insecticide control. Damage is usually aesthetic, and chemical control is typically not needed. The use of insecticides is highly ill-advised, as application timing would be just before or during peak bloom, causing high risk to pollinators and non-target insects.  

Organic Strategies:

Strategies 1 and 2 are strictly organic approaches. 

Pesticide Disclamer:

Always follow the product's label and ensure the product is effective against weevils. Not following the pesticide label before usage is a violation of federal law.