Not all plants will express resistance to leafhoppers. The exact mechanism of PLH resistance is not known, but is associated with the presence of glandular hairs on alfalfa leaves and stems. University and Pioneer data demonstrate a proven yield advantage for PLH resistant varieties under moderate to heavy leafhopper pressure. This Crop Insights provides information on variety development, resistance mechanisms and management of PLH resistant varieties. Expression of Resistance in Alfalfa Varieties Individual plants in an alfalfa variety are similar but not identical Alfalfa varieties differ from corn hybrids in their expression of pest resistance.
Corn is a hybridized crop.
Each seed contains an identical genetic code, so each corn plant expresses the same level of resistance to a pest. An alfalfa variety, on the other hand, consists of a population of plants that are similar but not identical. Individual plants exhibit a range of resistance to a given pest, even though the variety as a whole may be characterized as resistant. Because individual plants differ for resistance, rating alfalfa varieties could prove inconsistent. This problem is addressed by the development of an industry-wide standard rating system.