Varietal differences in the susceptibility of Brussels sprouts to lepidopterous pests

The attack by cabbage caterpillars on open-pollinated cultivars of Brussels sprouts at Wellesbourne was recorded approximately weekly from July to October in 1973 and 1974. The red-foliaged cv. Rubine was much less attacked by Pieris rapae than any of the twenty-five green-foliaged cultivars tested, the least attacked of which were The Aristocrat, Continuity, Evergreen and Pride of the Market. Rubine also showed some resistance to attack by Mamestra brassicae and Evergestis forficialis, as did The Aristocrat. Continuity, though as resistant as any of the cultivars to E. forficialis, was not resistant to M. brassicae. No evidence of antibiosis was found and resistance, based on non-preference, is considered to result from ovipositing P. rapae adults discriminating against the red colour of Rubine and against the leaf composition (relative volatile content) of the green-foliaged resistants. This could also apply with M. brassicae and E. forficialis.