The ability of varieties within a plant species can differ in their ability to defend themselves against a plant pest or pathogen. The International Seed Federation (ISF) defines resistance as ‘the ability of a plant variety to restrict the growth and development of a specified pest or pathogen and/or the damage they cause when compared to susceptible plant varieties under similar environmental conditions and pest or pathogen pressure. Resistant varieties may exhibit some disease symptoms or damage under heavy pest or pathogen pressure.’
To promote consistency in terms by vegetable seed companies relating to resistance, the ISF Vegetable and Ornamental Crops Section has adopted definitions for Immunity, High resistance, Moderate resistance, and Susceptibility.
Use of resistant varieties limits the impact of pests and should be used whenever available and horticulturally suitable. In vegetable production, there are a range of varieties, resistant to a range of insect pests and diseases, across crop types. To obtain information about resistant varieties suitable to your climate and requirements, speak to seed company representatives and rural supply stores. Some common pests for which resistant varieties are available are: Fusarium wilt; Tomato spotted wilt virus (TSWV); Powdery mildew; Downy mildew; Cucumber mosaic virus (CMV); White blister; Root-knot nematode; and Currant lettuce aphid (CLA).