Diadegma semiclausum Hellén
(Also known as Diadegma cerophagus (Gravenhorst).
Systematic position: Insecta, Holometaboa, Hymenoptera, Apocryta, Chalcidoidea, Ichneumonidae.
Geographic distribution: The probable origin of this species is Africa, but it has been introduced into many regions and is now almost cosmopolitan.
Morphology: Females are shiny black, with yellow legs and very long antennae, about 3-4 mm in length.
Life history: Diadegma semiclausum is a parasitoid of the diamond-back moth, Plutella xylostella. A life cycle is completed in 12-16 days, from egg laying (up to 700/female) in the host (usually a young larva) to adult emergence. If honey and nectar are available, adults can live up to 25 days, but without food survival is only 3 days. It is a strong flier. Although usually more abundant in cooler regions, a strain from Syria showed some heat tolerance, which could be used to introduce D. semiclausum into warmer regions for pest control.
Economic importance: Diadegma semiclausum is a major natural enemy of P. xylostella. It has been introduced, and had become established in various regions, even when only 150-300 adults were released. The parasitoid has attacked and killed as many as 70%, or more, of pest populations in many parts of the world. It has the ability to move 15-30 km from release sites, and in Eastern Africa it displaced indigenous parasitoids of P. xylostella.
Effect of pesticides: Carbamates and pyrethroids are very toxic to D. semiclausum, but inhibitors of Chitin synthetase had little effect.
References
Abbas, M.S.T. 1988. Biological and ecological studies on Diadegma semiclausum Hellen (Hym., Ichneumonidae), a larval parasite of the diamond-back moth, Plutella xylostella (L.) (Lep., Plutellidae) in Egypt. Anzeiger für Schädlingskunde, Pflanzenschutz, Umweltschutz 61: 1–2
Gichini, G., Lohr, B., Rossbach, A., Nyambo, B. and Gathu, R. 2008. Can low release numbers lead to establishment and spread of an exotic parasitoid: the case of the diamondback moth parasitoid, Diadegma semiclausum (Hellen), in East Africa. Crop Protection 27: 906–914.
Haseeb, M., Amano, H. and Nemoto, H. 2000. Pesticidal effects on mortality and parasitism rates of Diadegma semiclausum, a parasitoid of the diamondback moth. BioControl 45: 165-178.
Juric, I., Salzburger, W. and O. Balmer, O. 2017. Spread and global population structure of the diamondback moth Plutella xylostella (Lepidoptera: Plutellidae) and its larval parasitoids Diadegma semiclausum and Diadegma fenestrale (Hymenoptera: Ichneumonidae) based on mtDNA. Bulletin of Entomological Research 107: 155-164.
Kadirvel, P., Srinivasan, R., Lin, M.-y., Al-Jouri E., Walid, I.M. and de la Peña, R.C. 2011. Occurrence of Diadegma semiclausum, a parasitoid of diamondback moth in lowlands of Syria. Journal of Asia-Pacific Entomology 14 52–57.
Löhr, B., Gathu, R., Kariuki, C., Obiero, J. and Gichini, G. 2007. Impact of an exotic parasitoid on Plutella xylostella (Lepidoptera: Plutellidae) population dynamics, damage and indigenous natural enemies in Kenya. Bulletin of Entomological Research 97: 337-50.
Sarfraz , M., Keddie, A.B. and Dosdall L.M. 2005. Biological control of the diamondback moth, Plutella xylostella: a review. Biocontrol Science and Technology 15: 763–789.
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