The seasonal history of the grape phylloxera, Phylloxera vitifoliae (Fitch), infesting vine roots in commercial vineyards in the Niagara Peninsula, Ontario, was investigated from 1960 to 1963, mostly on the variety Delaware. Galls caused by the phylloxera feeding on actively-growing feeder rootlets first appeared about mid-June, and increased to a maximum in late August or early September. Numbers of phylloxerae on the infested roots increased during the season until hibernation. Nymphs of the winged form of phylloxera were first found on the roots on dates ranging from 16 July to 22 August, and continued to occur for 11/2 to 21/2 months. Hibernation usually began in the latter part of September, and reached 90% between 2 and 23 October. Usually fewer than 10% of the hibernants survived the winter.

There were more infested vines, more galled roots, and relatively more phylloxerae in vineyards on clay loam soil than in sandy loam.

Hibernants resumed activity in the laboratory in a few days at room temperatures, and became adults in as little as 10 days.