Centaurea cyanus
"Centaurea cyanus" was found to produce volatiles attracting "Microplitis mediator", which is a major parasitoid of the cabbage moth ("Mamestra brassicae"), which is the most important pest of cabbage ("Brassica oleracea") in central Europe. Planting "Centaurea cyanus" in cabbage fields as a companion plant was thus suggested as an alternative to the widespread use of insecticides to control "Mamestra brassicae". Field experiments showed that planting "Centaurea cyanus" in cabbage fields at a density of 1 plant / m2 can result in a significant increase in parasitation of "Mamestra brassicae" larvae, predation of "Mamestra brassicae" eggs (e.g. by carabid beetles or spiders) and ultimately cabbage yield.