A new method is described for artificially infesting grape clusters with eggs of Lobesia botrana (Denis and Schiffermuller). Eggs were released at different densities (4, 8, 10, 16, and 40 eggs per cluster) and at different stages of development. The intermediate ''visible mandibles'' embryonic stage was more appropriate for infestation than the ''visible ocelli'' or ''dark head capsule'' stages. The results were not significantly influenced by climatic conditions as tested in a controlled environment corresponding to hot and cool Bordeaux summer periods. This technique was applied in vineyards near Bordeaux in 1988 using ''Semillon', 'Sauvignon', 'Cabernet Franc', 'Cabernet Sauvignon', and 'Merlot.' We also confirmed experimentally in the greenhouse that cluster looseness had an adverse effect on the survival of larvae at bloom and during berry development. The effectiveness and the advantages of this technique for use in field trials over artificial infestations using newly hatched larvae are discussed.