Epigean development of grape phylloxera, Viteus vitifoliae (Fitch), in Tuscan nurseries of American vines, during the years 1982–1983

In the two-year period of 1982–1983, during sampling for studies on Viteus vitifoliae (Fitch) population dynamics on American vine rootstocks, there were various fluctuations in the population which hindered identification of the number of the possible generations produced by the insect. With the aid of theoretic constants obtained through laboratory data and concerning the length of the aphid generation, it was possible to identify the number of actual generations performed by the gallicolae form.