Multiplication possibilities of an ecotype of the aphid Cedrobium laportei (Homoptera Lachnidae) on various provenances of the genus Cedrus.

The aphid, Cedrobium laportei, is one of the dangerous insect pests affecting cedar in France and in Europe. The multiplication possibilities of an aphid ecotype from an artificial cedar stand (the Petit Luberon in the Vaucluse department) were studied from 1996 to 2000, in temperature-controlled chambers and by artificial infestation of young plants from various areas. The plants belonged to the four species of Cedrus and to two hybrid species: C atlantica x C. brevifolia, C atlantica x C libani. The three French C atlantica provenances showed a high susceptibility to C laportei. In contrast, the aphid never developed on a provenance of C brevifolia from Cyprus. One provenance of C. deodara from Afghanistan would resemble the susceptible provenances. Overall, 14 C. libani provenances of Turkish origin and four of Lebanese origin were compared in 1997 and 1998. The Turkish group was proved to be very heterogeneous. Some of these provenances were more susceptible than those of C atlantica. Others, originating from eastern areas (> longitude of 33 degrees) such as "Aslankoy", were much less susceptible. Further to the east, there was practically no multiplication of C. laportei on the provenances from Lebanon and Cyprus. The multiplication possibilities of C. laportei on the two hybrid species were limited. Cedar stands in France, the oldest of which go back to the end of the nineteenth century, are made up of C. atlantica provenances which are susceptible to the aphid and which have been hard-hit from time to time. The challenge in the past has been to successfully introduce from North Africa a parasitoid specific to the species. At this time, we have species with varying degrees of resistance to the aphid at our disposal. In France, C. brevifolia should be reserved for ornament. The hardy growth of the Turkish (Aslankoy) C. libani provenance should be used in reforestation. The other forestry characteristics of the species from Lebanon and the hybrid species need to be established.