Patterns of seasonal abundance of Colorado potato beetle, Leptinotarsa decemlineata (Say), potato flea beetle, Epitrix cucumeris (Harris), potato leafhopper, Empoasca fabae (Harris), and aphids on potato cv. Norland are reported for the 1983–1985 growing seasons in southern Manitoba. Each year, Colorado potato beetles and potato flea beetles underwent one generation on the crop. There were two peaks of leafhopper abundance in 1983 and 1984, but only one was evident in 1985. Aphid populations rose to a single peak in August of each year.
In experimental plots in the absence of insecticides, Colorado potato beetles completely defoliated plants in two seasons out of the three. In commercial fields, insecticide sprays applied in July and early August greatly reduced populations of Colorado potato beetles for the rest of the season, and there was no defoliation at harvest. Insecticides had less effect on potato flea beetle populations. Leafhopper and aphid populations were small at the time of spraying.