BIOLOGICAL-CONTROL OF THE DAMSON-HOP APHID, PHORODON HUMULI (HOM., APHIDIDAE), USING THE LADYBEETLE HARMONIA-AXYRIDIS (COL., COCCINELLIDAE)

The possibility of using Harmonia axyridis (Pallas) to control the dam son-hop aphid Phorodon humuli (Schrank) in a dwarf-hop garden was stud ied in northern France in 1994 and 1995. Second and third instar larva e of H. axyridis were released at different stages of the aphid popula tion increase (early, at the time of insecticide treatment threshold w as exceeded and late). In the control, the number of aphids reached 19 1.3 +/- 30.8 per leaf at the end of June. In the plots where 50 larvae per plant were released, the best control was obtained when larvae we re released early and the aphid population was approximately 20 per le af. In this case, the average number of aphid per leaf did not exceed 54.5 +/- 10.3 aphids at the end of June, which is lower than the insec ticide treatment threshold of 80 aphids per leaf. Indigenous predators , especially Adalia bipunctata L., complemented the effect of H. axyri dis.