Abstract. The number of Brevicoryne brassicae colonies and the density of aphids on plants varied depending on broccoli cultivars and the year studies. In 2002 parasite Diaeretiella rapae played a great role in reduction of cabbage aphid population.

The occurrence of cabbage aphid (Brevicoryne brassicae L.)
and its natural enemy on different broccoli cultivars

Summary

In 2002-2003 the dynamics of population growth of Brevicoryne brassicae and its parasitation by Diaeretiella rapae was observed on eleven broccoli cultivars. The occurrence of predatory insects (from Chrysopidae, Coccinellidae and Syrphidae) in colonies of B. brassicae was noted too. In 2002 the number of aphids and the number of colonies on plants were not high but found differences for population of B. brassicae between the studied broccoli cultivars. In this year the parasite Diaeretiella rapae was an important factor decreasing the number of cabbage aphids. In 2003 a highly developed population of B. brassicae and a low parasitation of its colonies were observed. On the broccoli plants a small quantity of predatory insects was observed.