THE USE OF HARMONIA-AXYRIDIS LARVAE (COLEOPTERA, COCCINELLIDAE) AGAINST MACROSIPHUM-ROSAE (HEMIPTERA, STERNORRHYNCHA, APHIDIDAE) ON ROSE BUSHES

Third and fourth instar larvae of Harmonia axyridis were released in s pring into rose beds infested by the aphid Macrosiphum rosae. These bi ological treatments induced stabilization or a decrease of the aphid p opulations. Their efficiency is comparable with that of chemical treat ments performed in neighbouring rose beds and the subsequent developme nt of aphid populations was the same after these two types of treatmen ts. The rearing condition of H. axyridis, particularly its feeding on a substitute prey (lepidopteran eggs), the climate, particularly the r ainfall and low temperatures, sometimes near the development threshold of the coccinellid, and possibly the rose bush variety did not seem t o affect its potential predatory efficiency. An aphid density of more than thirty aphids per rose bush appears to be necessary for the larva e to remain on the plants, when fifty larvae were released per four bu shes.