RHS Level 3 – R3103 5.3.
5.3. State the importance of varietal selection.
In the context of organic gardening, ‘varietal selection’ simply means choosing the best variety for your purpose, having consideration to local conditions (climate, soil, etc.) and the pests and diseases that are most problematic in your area. For example, it is often possible to find cultivars that are resistant to, or at least less susceptible to, a problematic pest or disease.
An example is carrot fly (Psila rosae). A number of carrot cultivars have been developed that are less susceptible than average to carrot fly, including ‘Fly Away’, ‘Maestro’, ‘Resistafly’ and ‘Sytan’. These cultivars are not fully resistant, but they are a good choice for growers in areas where carrot fly is a problem, especially if the grower does not want to use chemical treatments.
Image: Shutterstock. Netting is often used to create a physical barrier against carrot fly.