A technique for studying the population dynamics of the cabbage aphid Brevicoryne brassicae (L.)

A method of obtaining information on the population ecology of the cabbage aphid Brevicoryne brassicae in the field is described.It is based on examination of colonies of nymphs which are all of the same age and which are checked daily until the death of the last individual. The results were used to develop a limited number of survivorship curves and life tables. The survival figures showed a steady, continuous loss of aphids in the first three nymphal instars, but the rate of loss increased in the fourth and adult instars. Mortality was induced by a parasite, Diaeretiella rapae (Mcintosh), predators, and by nymphs and adults falling from the leaves and failing to regain them. During the period of the study (summer), losses from parasitism by D. rapae were substantial in the adult stage. Some preliminary ideas on sampling procedure in population studies of B. brassicae are presented and discussed.