Resistance in Crop Species of the Genus Brassica to Oviposition by the Turnip Root Fly, Hylemya floralis

Root damages, surviving plants, difference in green mass yield between pesticide treated and untreated plants, and egg numbers were used to demonstrate and measure the resistance to the turnip root fly. The relative susceptibility varied both between crops and between cultivars. Resistance to oviposition is concluded to be an attractive possibility of controlling this pest. Tarsal contact with chemical stimuli on the landing surface is the most decisive oviposition factor. The chosen strategy is to facilitate the breeding selection by isolating and visualizing chemical resistance characters on the plant surface with modern chromatographic methods. Condensed surface washings obtained by squirting steam over fresh leaves were applied on leaf dummies. Chemical agents contributing to the difference in egg-laying were in this was washed off from a susceptible cultivar of Chinese cabbage and a resistant cultivar of kale. The difference in eggload between the extracts is caused by accessory oviposition activators in an isolated fraction of Chinese cabbage. These results may be used for a breeding selection of less susceptible Chinese cabbage.