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common name: parasitoids of dipteran leafminers
scientific name: Diglyphus spp. (Insecta: Hymenoptera: Eulophidae)

Introduction - Distribution - Description and Life Cycle - Hosts - Economic Importance - Selected References

Introduction (Back to Top)

Diglyphus spp. wasps are promising biological control agents for agromyzid leafminers (Diptera: Agromyzidae). The species occurring in North America are Diglyphus isaea (Walker), D. begini (Ashmead), D. websteri (Crawford), D. intermedius (Girault), D. pulchripes (Crawford) and D. carlylei (Girault) (Lasalle and Parrela 1991, Stegmaier 1972).

Adult Diglyphus sp. on a bean leaf. Larvae in this genus are external parasitoids of dipteran leafminers.

Figure 1. Adult Diglyphus sp. on a bean leaf. Larvae in this genus are external parasitoids of dipteran leafminers. Photograph by Jian Li, University of Florida.

Distribution (Back to Top)

This genus of leafminer parasitoids occurs widely in Asia, Europe, North America, New Zealand and Northern Africa (Minkenberg 1989).

Description (Back to Top)

Adult: The adult parasitoid is a tiny wasp 1.5–2 mm long, depending on the species. The head, thorax and dorsal abdomen are generally metallic green in color, while the eyes are red. The scutellum has two pairs of setae, a submarginal vein with more than two dorsal setae, and the funicle is 2-segmented (Lasalle and Parrell 1991).

Adult Diglyphus sp. on a bean leaf. Larvae in this genus are external parasitoids of dipteran leafminers.

Figure 2.  Adult Diglyphus sp. on a bean leaf. Larvae in this genus are external parasitoids of dipteran leafminers. Photograph by Jian Li, University of Florida.

Egg: The adult female Diglyphus parasitoid stings the dipteran host larva to paralyze it. Then the female may lay one or more eggs on the late instar leafminer larva (Minkenberg 1986).

Larva: The parasitoid larva has three instar stages. The first instar larva is transparent, whereas second and third instars are yellowish. The parasitoid larva feeds externally on the leafminer larva, eventually killing the host. The parasitoid larva then pupates in the leaf mine before emerging as an adult. The development time is temperature dependent. Diglyphus isaea takes about 10 days at 25°C for complete development on both the American serpentine leafminer, Liriomyza trifolii; and the pea leafminer, L. huidobrensis (Bazzocchi et al. 2003).

Diglyphus sp. larvae, 1st, 2nd and 3rd instar respectively left to right. The larvae were removed from the mine of a bean leaf. Larvae in this genus are external parasitoids of dipteran leafminers.

Figure 3.  Diglyphus sp. larvae, 1st, 2nd and 3rd instar respectively left to right. The larvae were removed from the mine of a bean leaf. Larvae in this genus are external parasitoids of dipteran leafminers. Photograph by Jian Li, University of Florida.

Parasitoid Diglyphus sp. larva (top) feeding on a leafminer larva. The larva was removed from the mine of a bean leaf. Larvae in this genus are external parasitoids of dipteran leafminers.

Figure 4. Parasitoid Diglyphus sp. larva (top) feeding on a leafminer larva. The larva was removed from the mine of a bean leaf. Larvae in this genus are external parasitoids of dipteran leafminers. Photograph by Jian Li, University of Florida.

Two parasitoid Diglyphus sp. larvae (one is feeding horizontally on top, the second is positioned vertically to the right side of the larger host larva) feeding on a leafminer larva. The larvae were removed from the mine of a bean leaf. Larvae in this genus are external parasitoids of dipteran leafminers.

Figure 5. Two parasitoid Diglyphus sp. larvae (one is feeding horizontally on top, the second is positioned vertically to the right side of the larger host larva) feeding on a leafminer larva. The larvae were removed from the mine of a bean leaf. Larvae in this genus are external parasitoids of dipteran leafminers. Photograph by Jian Li, University of Florida.

Pupa: The third instar larva pupates in the leaf mine. The pupa is initially both transparent and light green, but eventually turns black.

Early stage of pupa of a Diglyphus sp. showing transparent and light green color, and red eyes (on right). The pupa was removed from the mine of a bean leaf. Larvae in this genus are external parasitoids of dipteran leafminers.

Figure 6. Early stage of pupa of a Diglyphus sp. showing transparent and light green color, and red eyes (on right). The pupa was removed from the mine of a bean leaf. Larvae in this genus are external parasitoids of dipteran leafminers. Photograph by Jian Li, University of Florida.

Late stage of pupae of Diglyphus spp. turn black in color. In this image the head is to the right. Larvae in this genus are external parasitoids of dipteran leafminers.

Figure 7.  Late stage of pupae of Diglyphus spp. turn black in color. In this image the head is to the right. Larvae in this genus are external parasitoids of dipteran leafminers. Photograph by Jian Li, University of Florida.

Hosts (Back to Top)

Diglyphus spp. are primary ectoparasitoids of dipteran leafminers in the family Agromyzidae. However, a Diglyphus sp. was also recorded parasitizing Lepidoptera (Lyonetiidae) larvae (Boucek and Askew 1968).

Economic Importance (Back to Top)

Augmentative release of commercial Diglyphus spp. is used for controlling leafminers in greenhouses in North American and Europe. Bazzocchi et al. (2003) indicated that D. isaea parasitized at least 18 different agromyzid species. Diglyphis isaea is the most effective commercial biological control product for controlling the American serpentine leafminer, Liriomyza trifolii; the pea leafminer, L. huidobrensis; L. bryoniae; and the chrysanthemum leafminer, Phytomyza syngenesiae (Syngenta-bioline). Lasalle and Parrella (1991) indicated that D. begini also parasitizes L. trifolii, L. huidobrensis and L. bryoniae in North America. Kaspi and Parrella (2005) reported that the insecticide Abamectin has little impact on D. isaea adults or the larvae within the leaf mines of chrysanthemums.

Selected References (Back to Top)