63 Attraction of Naive Diadegma semiclausum Hellen (Hymenoptera: Ichneumonidae) Females and Cotesia vestalis (Haliday) (Hymenoptera: Braconidae) to Cabbage (Brassica oleracea) Plant Volatile Organic Compounds Using the Olfactometer and Screen-Cage Methods ISMAIL A., MANSOUR S.1, MOHAMED ROFF M.N. 2 , NADIA M. KERMANI 3 MOHD HANAIFH YAHAYA 4 , IDRIS A.B. 5 School of Environmental and Natural Resource Science, Faculty Science & Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia E-mail: iabozid@yahoo.com 1 Omar Al-Mukthar University. Zoology Department, P.O. Box. 919 Al-Bidya Libya. E-mail: mansour_sm2001@yahoo.com 2 Deputy Director/ Senior Principal Research Officer, Pest and Disease Management Programme, Horticulture Research Centre, MARDI HQ, P.O. Box 12301, GPO, 50774 Kuala Lumpur, Malaysia. E-mail: roff@mardi.gov.my 3 School of Environmental and Natural Resource Science, Faculty Science & Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia. E-mail: nadia.khermani@yahoo.com 4 Horticulture Research Centre and Strategic Resources Research Centre MARDI Headquarter Persiaran, MARDI-UPM, 43400, Serdang Selangor, Malaysia E-mail: hanifah58@yahoo.com 5 School of Environmental and Natural Resource Science, Faculty Science & Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia. E-mail: idrisgh@ukm.edu.my ABSTRACT Volatile organic compounds (VOCs) released by plant when attacked by herbivores could play a very important role in the indirect defense of host plants by attracting natural enemies of the attacking herbivore. The hymenopteran parasitoids, Diadegma semiclausum (Hellen) (Hymenoptera: Ichneumonidae) and Cotesia vestalis (Haliday) (Hymenoptera: Braconidae) are important biological control agents of the diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), the most important pest of cruciferous crops worldwide. These parasitoids use plant volatiles in their in-flight searching behavior. The objectives of this work were to determine the effects of the VOCs emitted by differently damaged Cabbage (Brassica oleracea L.) plants on the attracting response behavior of C. plutellae and D. semiclausum adult females using olfactometer and screen cage methods. Results showed that the naive females for each parasitoid discriminated separately between odors from plants damaged mechanically, by aphids, by cabbage leaf webber (Crocidolomia pavonana Zeller) larvae or by larvae of DBM. No comparison study between parasitoid species was detected. The plants that fed by C. pavonana larvae or mechanically were more attracted to the adult females D. semiclausum than intact plants in the olfactometer study. In the screen cage method, however, the plants damaged by DBM larvae were more attractive to the Diadegma females than to all other plants damaged by other types of damage. For C. vestalis, the females tested using olfactometer was also showed high significant preference to plants damaged by C. pavonana larvae, while plants damaged by DBM larvae were significantly preferred than to the C. pavonana by the naive females. Understanding the attraction of the VOCs emitted by host plants damaged by host or non-host larvae of these parasitoids may help us to discover the possibility of using plant-pest-parasitoid interactions for improving an integrated DBM management. Keywords: Diadegma semiclausum, Cotesia vestalis, Plutella xylostella, Brassica oleracea, volatile organic compounds Mysore J. Agric. Sci., 51(A): 63-68, 2017