Striped cucumber beetle parasitoid (Celatoria setosa)

Biocontrol Agent

Celatoria setosa is a parasitoid tachinid fly species that targets the striped cucumber beetle (Acalymma vittatum).

Overview

Pests Targeted: Acalymma vittatum
Pest Stage: Adult
Commercially Available? No
Scientific Name: Celatoria setosa
Biocontrol Agent Type: Parasitoid

Close-up photo of a small fly with red eyes and a comparatively long, hook-shaped ovipositor protruding from its abdomen — The large, hook-shaped ovipositor helps to identify this fly as a parasitoid of striped cucumber beetle. Image credit: Matthew Barrett

Common Names

Striped cucumber beetle parasitoid

Relative effectiveness

This parasitoid fly can help reduce striped cucumber beetle populations but is likely not sufficient as the only control method. Multiple field surveys have reported parasitism rates exceeding 40% during peak beetle populations.

Where to use

All cucurbit crops
Outside

About the striped cucumber beetle parasitoid

Celatoria setosa is a parasitoid natural enemy of the striped cucumber beetle (Acalymma vittatum). Like other tachinid fly species, it also feeds on nectar and pollen and can often be found feeding from the nectaries of various flowering cucurbit crops.

Native/Non-native: Native
Preferred climate: Temperate, cold tolerant
Region: Midwestern, mid-Atlantic, and northeastern regions of the United States
Established: Yes
Where established: Midwestern, mid-Atlantic, and northeastern U.S.; range may extend as far south as the southernmost populations of its host

Striped cucumber beetle parasitoid appearance

Adult parasitoids are small (up to 4 mm, or less than a quarter of an inch, in length) black-bodied flies with red eyes. Although they often hide among crop foliage, they can be spotted by their distinctive flight patterns and behaviors. They fly in erratic, spiraling motions through the plant foliage and crawl across leaves, likely in search of host beetles. When captured, female parasitoids can be easily identified by their characteristic enlarged, sharp, hook-shaped ovipositor, which is used to insert their young – actually a live larva, rather than an egg – into host beetles.

The large, hook-shaped ovipositor helps to identify this fly as a parasitoid of striped cucumber beetle.
Image credit: Matthew Barrett

Small fly perched on a yellow cucurbit flower

The nectar of cucurbit flowers can also be an important food source for this fly parasitoid of striped cucumber beetle.
Image credit: Matthew Barrett

Learn more about the life cycle of Celatoria setosa

C. setosa is an obligate parasitoid, meaning it exclusively targets A. vittatum. The fly parasitizes adult beetles by injecting a single first instar parasitoid larva into the thorax of the host. The life cycle typically takes around three weeks to complete: parasitoid pupae emerge from the host beetles 9-14 days after parasitism, and adult flies eclose 6-9 days after pupation. C. setosa overwinters in host beetles as larvae, and first-generation adult parasitoids emerge in the weeks following the appearance of striped cucumber beetles, usually in late May to early June. However, parasitoids can be found throughout the growing season in cucurbit fields.

In the larval stage, C. setosa larvae reside individually inside their host beetles, feeding on beetle resources as they grow. As final-instar larvae, they emerge from the host beetles and fall to the soil, killing the host in the process. The parasitoid larvae pupate in the soil and remain there until they eclose as adult flies. Upon eclosion, male and female C. setosa mate within the first few hours, after which females begin searching for both plant resources and new host beetles for their offspring.

How to use the striped cucumber beetle parasitoid

Biocontrol category: Conservation

When to use: The most effective way to use C. setosa for biological control is by supporting their populations in your area.

Maximizing effectiveness: Since C. setosa parasitoids rely on adult A. vittatum beetles as hosts, using control tactics that target adult beetles may unintentionally harm the parasitoids. Consider management strategies that target different pest life stages.

Mode of action: Parasitoid

Conservation: Similar to other insect natural enemies, these parasitoid flies can be conserved through diversifying crops, growing cover crops, reducing pesticide use, and enhancing natural habitats for the flies. Higher relative humidity and plenty of nectar-rich flowers – especially cucurbit flowers – are also critical.

Compatibility: There has not yet been any research to assess C. setosa compatibility with commercial pesticides, but it is likely sensitive to many of them.

Risk: These flies only parasitize striped cucumber beetles and do not sting or bite humans.

Commercially available: No

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.

About pests targeted by the striped cucumber beetle parasitoid

Striped cucumber beetle adults are common cucurbit pests found in a variety of settings, from backyard gardens to large commercial farms. These small beetles, about 7 mm (3/8 in) in length, have black heads, yellowish thoraxes, and distinctive black and yellow vertical stripes on their elytra (hardened wing covers). This species is gregarious and often forms dense aggregations on plant foliage during the early growing season or inside flower blossoms in mid to late summer. The larval stages of striped cucumber beetles are typically found burrowing in the soil near the base of crop stems, where they feed on roots belowground.

Pest damage

Striped cucumber beetles are highly destructive pests, particularly during the early growing season when plants are still small and in the seedling stage. Their destructive impact varies by life stage and season. In the early season, adults rapidly colonize young plants in high densities, laying eggs in the soil that hatch into larvae, which then damage the roots. Later in the season (typically the second generation in July), beetles target cucurbit flowers, where they damage the nectaries. This is also when they often transmit disease such as bacterial wilt, caused by Erwinia tracheiphila, and spread through defecation in the nectaries and on damaged foliage.

Black and yellow striped beetles feeding on the leaves of a young cucurbit plant

Striped cucumber beetles are especially destructive of young cucurbit plants.
Image credit: Matthew Barrett

Many black and yellow striped cucumber beetles on a cucurbit leaf full of holes

High populations of cucumber beetles can damage cucurbit foliage.
Image credit: Amara Dunn-Silver

Two black and yellow striped cucumber beetles on a cucurbit leaf

Striped cucumber beetles mating.
Image credit: Jensen Njagi

Author

Matthew Barrett
Department of Entomology, Cornell College of Agriculture and Life Sciences

Last updated: January 2025

Photos and Illustrations

"The large, hook-shaped ovipositor helps to identify this fly. . ." Photo by Matthew Barrett, Department of Entomology, Cornell CALS
"The nectar of cucurbit flowers can also be an important food source. . ." Photo by Matthew Barrett, Department of Entomology, Cornell CALS
"Striped cucumber beetles are especially destructive. . ." Photo by Matthew Barrett, Department of Entomology, Cornell CALS
"High populations of cucumber beetles can damage cucurbit foliage"—Photo by Amara Dunn-Silver, Senior Extension Associate, NYS Integrated Pest Management
"Striped cucumber beetles mating"—Photo by Jensen Njagi, Lab Research Assistant, Cornell CALS