Imported Cabbageworm Parasitoid (Cotesia glomerata)
Biocontrol Agent Factsheet
C. glomerata was introduced to North America in 1883 as a part of a classical biological control program for the control of the imported cabbageworm, and has become a major mortality factor of cabbageworm populations.
Overview
Pests Targeted: Imported Cabbageworm
Pest Stage: Larva
Commercially Available? No
Scientific Name: Cotesia glomerata
Biocontrol Agent Type: Parasitoid

Common Names
Imported cabbageworm parasitoid
Relative effectiveness
Since their introduction to North America, parasitism rates by C. glomerata have been evaluated in the early season. C. glomerata parasitism in the early season has been deemed low, however, as the season progresses, parasitism rates increase. By midseason, about half of imported cabbageworm larvae are parasitized, and late in the growing season, that percentage has increased to 60-75%.
Where to use
Cole crops (e.g. Brussels sprouts, broccoli, cabbage, kohlrabi, cauliflower, collards, horseradish, kale, etc)
About Imported Cabbageworm Parasitoid
Cotesia glomerata (L.) is a parasitoid wasp of the imported cabbageworm (Pieris rapae) a serious pest of cabbage and other cole crops. C. glomerata was introduced to North America in 1883 as a part of a classical biological control program for the control of the imported cabbageworm, and has become a major mortality factor of cabbageworm populations.
- Native/Non-native: Non-native
- Preferred climate: Temperate
- Established: Yes
- Where established: North America
Imported Cabbageworm Parasitoid Appearance
Cotesia adults are small, about 3-7 mm in length, dark wasps that bear a resemblance to flying ants or tiny flies. Adults have yellowish-brown legs and curved antennae about 2 mm in length, but not elbowed upward.

Adult C. glomerata, cabbageworm parasitoid.

C. glomerata adult laying eggs in (parasitizing) a caterpillar.
How to Use Imported Cabbageworm Parasitoid
Biocontrol category: Classical - released once and persists
When to use: Spring, as the emergence of first generation C. glomerata is temperature and light dependent with rates of parasitism increasing throughout the season.
Maximizing effectiveness: Beneficial insects are often not compatible with commercially available insecticides, and the use of herbicides can reduce the floral and nectar availability. Therefore, species of parasitoid wasp such as C. glomerata should be supported in organic production systems and low-risk agricultural regions where pesticide use is reduced.
Pest stage: Immature stage (larvae) that are typically first instars (smallest caterpillars). Female C. glomerata attack early cabbageworm larvae and deposit 20-60 eggs into their body cavities after altering the growth and development of their hosts to meet their own nutritional requirements. C. glomerata then emerge around the fifth instar.
Mode of action: Parasitoid
Conservation: Because C. glomerata is already established in North America, biological control programs should be focused on supporting populations of C. glomerata and other parasitoid wasps by providing adequate sources of nectar-producing plants as well as efforts to reduce the use of broad-spectrum insecticides near preferred locations.
Compatibility: In 1975, Hamilton and Attia demonstrated that C. glomerata are not compatible with commercially available insecticides on cole crops, and therefore population support requires careful consideration of broad-spectrum insecticide use. Additionally, the use of herbicides should also be considered when supporting populations of natural enemies, as herbicides can reduce floral and nectar availability that is often key to C. glomerata survival. (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.)
Risk: Parasitoid wasps are not a sting risk to humans.
Commercially available: No
About cabbageworm targeted by Cotesia glomerata
- Imported cabbageworm (Pieris rapae)
- Cabbage butterfly (Pieris rapae)
- White butterfly (Pieris rapae)
Cabbageworm larvae are green and fuzzy or velvety in appearance, at their largest they are typically 30 mm in length. The larvae typically complete their development in about 15 days under ideal conditions. Cabbageworm larvae have a distinct creamy-yellowish line running along the top of their back, however, this line is sometimes absent in early instars (young caterpillars). An additional broken yellow line, and a series of yellow spots, also appears on each side of the larvae.
Cabbageworm Damage
Cabbageworms feed widely on cruciferous plants, which is a family of plants that includes Brussels sprouts, broccoli, cabbage, kohlrabi, cauliflower, collards, horseradish, and kale. Cabbageworm feeding and tunneling damage occurs primarily in the leaves of these host plants, especially as they mature. If cabbageworm populations are left unchecked, they often will reduce mature plants to stems and large veins rendering the plant unmarketable.
Imported cabbageworm larva (P. rapae)


Cabbage butterfly (P. rapae) feeding on nectar.

Imported cabbageworm (P. rapae) feeding damage.

Cabbageworm (P. rapae) chrysalis (a hard exoskeleton covering that protects the butterfly during development) and feeding damage.
Cotesia glomerata (Hymenoptera: Braconidae)
Cotesia glomerata (L.) is a koinobiont endoparasitic wasp of the imported cabbageworm (Pieris rapae) a serious pest of cruciferous crops (e.g. broccoli, cabbage, cauliflower, collards, horseradish, kale, and kohlrabi; Capinera 2000; Hasan and Ansari 2010). C. glomerata was introduced to North America in 1883 as a part of a classical biological control program for the control of the imported cabbageworm on cole crops, and has become a major mortality factor of cabbageworm populations (Shelton 1992).
Cotesia adults are often observed in the field where cruciferous species are present, where they search diligently on foliage for cabbageworm larvae (Capinera 2000). Due to their high success as a parasitoid, dead cabbageworm larvae are often found in clusters of 20 to 30 with C. glomerata cocoons attached (Capinera 2000). Immediately after emerging, adult C. glomerata mate just before the female attacks early cabbageworm instars and deposits 20-60 eggs within the body cavities of first instar larvae. The parasitoid larvae egress from the host halfway through its fifth instar after altering the growth and development of their hosts to meet their own nutritional requirements (Gauld, 1988; Laing and Levin 1983; Hasan and Ansari 2012). Depending on the temperature, the Cotesia offspring develop from egg to adult in approximately 22-30 days within the maturing cabbageworm larva as it prepares to pupate. Cotesia adults live between 8-10 days under ideal conditions. Cotesia larvae emerge after about 15-20 days and spin their cocoons on or near the host which dies when the wasps emerge (Shelton 1992).
Cotesia adults are small, about 3-7 mm in length, dark wasps that bear a resemblance to flying ants or minute flies (Laing et al. 1982). Adults have yellowish-brown legs and curved antennae about 2 mm in length, but not elbowed upward. Due to their beneficial endoparasitic behavior, populations of C. glomerata were collected and released as a part of a North American classical biological control project in 1883 (Shelton 1992). Since their introduction to North America, parasitism rates by C. glomerata have been evaluated in the early season. C. glomerata parasitism in the early season has been deemed low, however, as the season progresses, parasitism rates increase. By midseason, about half of imported cabbageworm larvae are parasitized, and late in the growing season, that percentage has increased to 60-75%. Furthermore, C. glomerata may be an important vector in the transmission of the granulosis virus (Family: Baculoviridae) in imported cabbageworms (Levin et al. 1983). Granuloviruses are well known for their unique ability to completely liquify their hosts in order to spread to more hosts, a trait they share with the closely related nuclear polyhedrosis viruses. In addition, C. glomerata are resistant to attack by many hyperparasitoids.
Due to the complex nature of their reproduction, C. glomerata are not available for purchase from commercial rearing companies. Therefore, improved levels of cabbageworm parasitism through the use of C. glomerata can be achieved through attraction and support of C. glomerata populations, as well as other parasitoid wasp species. Studies like (Käfer et al. 2012) have shown that adult wasps die rapidly when temperatures exceed 90°F, consequently, supporting populations of parasitoid wasps involves maintaining non-crop habitats distributed on the edge of fields, as well as planting varieties of flowering plants that offer essential sugars, nectar, and pollen that can frequently be critical to wasp survival.
Beneficial insects are often not compatible with commercially available insecticides, and the use of herbicides can reduce the floral and nectar availability, therefore, species of parasitoid wasp such as C. glomerata should be supported in organic production systems and low-risk agricultural regions where the survivability and compatibility of the insect and ecosystem is not challenged by pesticide susceptibility. This is primarily due to studies demonstrating that C. glomerata and other parasitoid wasps have been shown to be susceptible to several pesticides commonly used on cole crops (Hamilton and Attia 1975).
Author
Lidia Komondy
Cornell University Department of Entomology
Date: November 2021
I would like to thank the Cornell University Department of Entomology Extension Outreach Program for their support.
Thanks to Saskya van Nouhuys, Department of Entomology, Cornell University, for providing material and for reviewing and making suggestions which have improved this section.
Modified from an article written by Anthony M. Shelton: Shelton, A.M. 1992. Cotesia (Apanteles) glomerata (Hymenoptera: Braconidae), Biological Control: A guide to Natural Enemies of North America.)
- Capinera, J. 2000. Imported cabbageworm, Pieris rapae (Linnaeus) (Insecta: Lepidoptera: Pieridae). EENY-126. EDIS, 2000.
- Feltwell, J., 1982. The Biology, Biochemistry and Physiology of Pieris brassicae (Linnaeus). Series Entomologica, vol. 18. Dr. W. Junk, The Hague.
- Gauld I.D. Evolutionary patterns of host utilization by ichneumonid parasitoids (Hymenoptera: Ichneumonidae and Braconidae) Biological Journal of the Linnean Society 1988; 35: 351-377.
- Hamilton, A.G. 1935. Miscellaneous observations on the biology of Apanteles glomeratus L. (Braconidae). Entomologist’s Monthly Magazine 71: 262-270.
- Hamilton, J.T. and Attia, F.I. 1975 The susceptibility of the parasite Apanteles glomeratus (L.) (Hym.: Braconidae) to insecticides. Journal of the Entomological Society of Australia 9, 1976: 24-25.
- Hasan, F., & Ansari, M. S. 2012. Superparasitism in Cotesia glomerata does not benefit the host plant by reduction of herbivory caused by Pieris brassicae. Saudi Journal of Biological Sciences 19(1), 65-71.
- Hasan F., Ansari M.S. 2011. Population growth of Pieris brassicae (L.) (Lepidoptera: Pieridae) on different cole crops under laboratory conditions. Journal of Pest Science 84:179-186.
- Laing, J.E.; Levin, D.B. 1982. A review of the biology and a bibliography of Apanteles glomeratus (L.) (Hymenoptera: Braconidae). Biocontrol News and Information 3 (1): 7-23.
- Levin, D.B., Laing, J.E., Jaques, R.P. and Corrigan, J.E. 1983. Transmission of the granulosis virus of Pieris rapae (Lepidoptera: Pieridae) by the parasitoid Apanteles glomeratus (Hymenoptera: Braconidae). Environmental Entomology 12: 166-170.
- McDonald, R.C. and Kok, L.T. 1991. Hyperparasites attacking Cotesia glomerata (L.) and Cotesia rubecula (Marshall) (Hymenoptera: Braconidae) in southwestern Virginia. Biological Control 1: 170-175.
- Matheson, R. .1907. The life-history of Apanteles glomeratus, L. Canadian Entomologist 39: 205-207.
- Shelton, A.M. 1992. Cotesia (Apanteles) glomerata (Hymenoptera: Braconidae), Biological Control: A guide to Natural Enemies of North America.
- Adult C. glomerata, cabbageworm parasitoid. Credit: 2018, New Zealand Arthropod Collection, Flickr.
- C. glomerata adult laying eggs in (parasitizing) a caterpillar. Credit: 2015, Lies Van Rompaey, Flickr.
- Adult C. glomerata, cabbageworm parasitoid. Credit: 2018, New Zealand Arthropod Collection, Flickr.
- C. glomerata parasitoid wasp life cycle.
- Cabbage butterfly (P. rapae) feeding on nectar. Credit: 2020, Antje Schultner, Flickr
- Imported cabbageworm larva (P. rapae). Credit: 2008, Sam Fraser-Smith, Flickr.
- Imported cabbageworm (P. rapae) feeding damage. Credit: 2021, Alabama A&M and Auburn University Extension, Flickr.
- Cabbageworm (P. rapae) chrysalis (a hard exoskeleton covering that protects the butterfly during development) and feeding damage. Credit: 2021, Alabama A&M and Auburn University Extension, Flickr.
- (315) 787-2206
- arc55 [at] cornell.edu