The effect of UV-absorbing plastic sheet on the attraction and host location ability of three parasitoids:: Aphidius colemani, Diglyphus isaea and Eretmocerus mundus

The effect of ultra violet (UV)-absorbing plastic sheets on the host location ability of three commercially available parasitoids Aphidius colemani Viereck (Hymenoptera: Braconidae), Diglyphus isaea Walker (Hymenoptera: Eulophidae) and Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) - was tested in the laboratory and in field trials. The parasitoids' preference between natural light and UV-filtered light was tested under laboratory conditions in a Y-shaped pipe system. The vast majority of all three species were strongly attracted to non-UV-filtered light. In field trials parasitoid's ability to locate a host-infested plant from a distance (approximately 10 m.) was tested. Host location by A. colemani and D. isaea, expressed by parasitization rates, was not affected by greenhouse covering plastic type (regular versus UV-absorbing plastic). E. mundus, on the other hand, was unable to locate the host-infested plant when the latter was placed in the center of the UV-absorbing plastic covered greenhouses. When the host-infested plants were located in the corners of the greenhouses and the wasps were released at the center, the parasitization rates were lower under the UV-absorbing plastic than under the regular plastic covered greenhouses. The significance of UV light to E. mundus host location process and the practical implications it has on the parasitoid's application in the field are discussed.