Aphid (Homoptera: Aphididae) Population Dynamics on Broccoli in an Interior Valley of California

Myzus persicae (Sulzer) was the most abundant aphid species encountered in fall and winter plantings of broccoli in Riverside County, Calif., during 1980 to 1981. Brevicoryne brassicae L. populations were smaller, but this species was of greater importance as a contaminant of broccoli. Aphid migration and density per plant were lower in the winter crop, but the potential for contamination was higher. Aphid species segregated by leaf choice, with M. persicae preferring the oldest leaves and B. brassicae the youngest. Plant age and growth affected aphid distribution. Sampling procedures based on 10-plant samples and leaf subsamples provided reliable estimates of aphid populations and may be suitable for scouting programs for aphids on broccoli.