The establishment ofRhyzobius forestieri [Col.: Coccinellidae] in greece and its efficiency as an auxiliary control agent against a heavy infestation ofSaissetia oleae [Hom.: Coccidae]

Introduction releases of the exotic coccinellid predatorRhyzobius forestieri Mulsant were made in 22 localities throughout Greece. The releases were made on olive, citrus, fig and almond trees infested with differentCoccidae scales. In 9 of these localities,R. forestieri was recovered 2–5 months later. The most important factor for the successful establishment ofR. forestieri seems to be an abundance of scales on the trees. To study the ability ofR. forestieri to enhance overall predation, 3 releases were made in an olive grove heavily infested withSaissetia oleae Olivier on Chios island during 1982 and 1983. The experiment began in June 1982. By April 1983, theS. oleae infestation was clearly in the process of being controlled by the coccinellid. A native coccinellid,Exochomus quadripustulatus L., contributed little during this period because of its obligatory estival diapause. The other main coccinellid,Chilocorus bipustulatus L., made an appreciable contribution toward achieving control during the summers of 1982 and 1983, but it was affected from July onward by increasing parasitism of its larvae. Both species are quiescent during the winter months. The introduced speciesR. forestieri was readily established in the olive grove and multiplied quickly. One month after the initial release,R. forestieri larvae made up most of the coccinellid larval population in the field. Thereafter until April 1983,R. forestieri larvae and adults comprised the dominant coccinellid population in the olive grove. During the winter months,R. forestieri remains active as long as temperature exceeds 8 °C. The important increase inR. forestieri's population size between July 1982 and April 1983 coincided with the increased rate of predation onS. oleae. This suggests thatS. forestieri played a key role in bringing theS. oleae infestation under control during this period. After April 1983, however, theR. forestieri population diminished rapidly andC. bipustulatus became the dominant coccinellid in the olive grove. It is believed that scarcity of prey was the cause of this reversal: by April 1983, the density ofS. oleae in the olive grove had already been reduced by about 100 times.