Feeding Site Preference of Potato Leafhopper (Homoptera: Cicadellidae) on Alfalfa and its Effect on Photosynthesis

摘要

The potato leafhopper, Empoasca fabae (Harris) (Homoptera: Cicadellidae), is a well-known pest of alfalfa in eastern North America. Its unique injury is associated with changes in host plant physiology, yet research to date has focused on the whole plant response. We conducted studies to determine the feeding site preference of nymphs and adults on alfalfa plants and to measure the impact of leaf and stem feeding on subsequent photosynthesis and stomatal conductance of leaves. Our observations of potato leafhopper nymphs in the field and of nymphs and adults in the greenhouse demonstrated contrasting (but variable) plant part preference for settling by the different leafhopper life stages: nymphs prefer leaves whereas adults prefer stems. In addition, CO_2 gas exchange measurements demonstrated that the location of leafhopper feeding on the plant surface affects the specific pattern of injury expressed in the physiology of alfalfa: leaf feeding impacts photosynthesis rate and stomatal conductance of the injured leaf alone whereas stem feeding impacts photosynthesis rate and stomatal conductance for leaves apical of the injured internode. Our results suggest that nymphs and adults likely cause different physiological effects on alfalfa, despite their equivalency in pest-management recommendations. Furthermore, the relationship between potato leafhopper injury, photosynthesis, and hopperburn remains unclear, and understanding the mechanisms would aid in predicting the level of damage associated with injury.