chalcidoid wasps
Superfamily Chalicidoidea
Scientific Names
Chalcidoids are members of a very large and diverse group of wasps, most of which parasitize other insects. Species include Aphelinus mali Haldeman (Family Aphelinidae), Trichogramma spp. (Family Trichogrammatidae), and others.
Identification
Members of two families, the Aphelinidae (Aphelinid wasps) and Eulophidae (Eulophid wasps), are more commonly seen in apple orchards, although Trichogrammatidae egg parasitoids may play a significant role as biological control agents.
- Aphilinid wasps
Eggs:
- Laid in host aphid
- Not observed
Larvae:
- Elongate and without features
- Not observed
- Parasitized woolly apple aphids are hardened, black and somewhat swollen
Pupae:
- Found within parasitized aphids
- Features such as legs and antennae becoming apparent, black
Adults:
- Small (0.6-4 mm)
- Yellow, brown or black wasps that lack a metallic appearance
- Wasp is slightly smaller than the aphid host in which it lays its eggs
- Circular exit holes are cut as it chews its way out of the dead aphid
- Eulophid wasps
Eggs:
- White, cylindrical and laid inside the leafminer mine – the host caterpillar
Larvae:
- Maggot-like – white, legless and elongate, up to 2.5 mm
- Found on the outside of the host leafminer larvae
Pupa:
- Recognizable by their mummy-like appearance when mines are opened
- Dark brown to black
- 2.5 mm in length, and are more robust than those of the host leafminer caterpillar
Adult:
- Small with metallic bodies
- The host is completely consumed by the developing wasp larva
- When mines are opened, all that remains is the wasp pupa and a small, circular hole in the mine through which the new adult escaped
Trichogramma wasps
Eggs:
- Laid directly into host insect egg, not observed
- Develop inside host egg
- Parasitized eggs appear black
- Minute wasps, 1mm or smaller, with red eyes and yellowish bodies
Often Confused With
Parasitic wasps are often difficult to distinguishing between each other. Learn to recognize the signs of parasitism in orchard pests.
Interaction With Host
Despite their small size (most are less than 3 mm in length) many chalcidoids are parasitoids of agricultural pests and are important biological control agents. Chalcidoids parasitize eggs, larvae or pupae of hosts. Female wasps lay their eggs on or in the host. Some larvae feed internally (endoparasitoids) while others attach to the host and feed externally (ectoparasitoids). The host insect is killed in the process.
Aphilinid wasps attack scale insects, whiteflies and aphids. In apple, A. mali is a key parasitoid of the woolly apple aphid.
Eulophid wasps represent the largest family of chalcidoid wasps. Most species parasitize concealed larvae, especially those inhabiting leaf mines such as the tentiform leafminer. Larvae are ectoparasitoids, meaning they develop externally on the affected hosts.
Trichogramma wasps parasitize eggs of other insects, particularly those of caterpillars. In apple orchards, Trichogramma spp. parasitize thee eggs of many economic pests such as those of codling moth and leafrollers.
Insects Attacked
Aphids, caterpillars, flies, scale insects, other.
Monitoring and Management
Chalcidoid wasps are most readily observed as larvae or pupae during monitoring activities for insect pests. Eulophid ectoparasitoids populations should be surveyed following leaf-sampling protocols for tentiform leafminer. Parasitoid larvae, pupae and partially consumed leafminers can be seen using a microscope when mines are opened. A. mali is susceptible to many insecticides and does not provide economic control in most commercial orchards.
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