Survey of Scale Insects and Their Natural Enemies in Riyadh Region ( Saudi Arabia )

A general survey of scale insects attacking fruit trees, shade trees and ornamental plants in Riyadh region was carried out throughout the year 1987 – 1988. Specimens were collected from the city of Riyadh as well as from the following surrounding village : Deriya , Uyayna , Huraymila , Quwayiya , Durma , Muzahimiya and Sanam. Ten species of scales were recovered : Aonidiella orientalis ( Newstead ) on a wide range of host plants; Parlatoria blanchardii ( Targ ) and Asterolecanium phoenicis Rao on Phoenix dactylifera : Parlatoria crypta McKenzie on Nerium oleander; Coccus longulus ( Douglas ) and C. hesperidium Linn.on Tipuana tipa; Saissetia oleae (Oliv.) on Ficus nitida; Parasaissetia nigra ( Nietner ) on F. carica; Contigaspis zillae ( Hall ) on F. nitida and Crotolaria aculeata, and Lecanodiaspis africana ( Newstead ) on F. carica and Acacia curenbergiana. The former species was the most dominant. It seems to be more adapted to the arid climate of the area. Previous surveys carried out in different regions of Saudi Arabia has been reviewed by Abu-Thuraya [ 1 ] who mentioned 31 species of scales belonging to 4 families and 19 genera. Matile-Ferrero [ 2, pp. 219-288 ] added several species to the previous list , 20 of which were recorded for the first time in Saudi Arabia. In the present work, 11 species of natural enemies emerged from infested scales; 7 parasitoids for A. orientalis, 3 for L. africana and a single predator for P. blanchardii . Eight of these ( marked by an asterisk ) were recorded for the first time in Saudi Arabia . The parasitoids of A. orientalis included 4 aphelinids; Marietta leopardina Mots.* , Encarsia aurantii ( Howard )* , E. sp. Nr citrina ( Craw )* , Azotus chrysomphali ( Ghesq.)*, and 3 encyrtids; Comperiella lemniscata Com. And Ann.* , C. aspidiotophaga Subba Rao and Haprolepis aspidiotii Com. And Ann. Two encyrtids, Lakshaphagus hautfeuilli ( Mahd )* and Parechthrodrynus combretae Risb.* and a single pteromalid, Scutellista sp. nr hispanica ( Masi ) were recorded as parasitoids of L. africana. The nitidulid Cybocephalus sp.* was the only predator recorded for P. blanchardii. This predator is probaply capable of attacking other scales species. Three species of parasitoids belonging to the genera Aphytis, Haprolepis and Aspidiotophaga were reared from the oriental scale insect, A. orientalis received in California with a shipment from Saud