Effects of Feeding by Potato Leafhopper Nymphs (Homoptera: Cicadellidae) on Growth and Quality of Established Stand Alfalfa

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Abstract
Damage to alfalfa by nymphs of the potato leafhopper, Empoasca fabae (Harris), was assessed in field studies during 3 years. First-instar potato leafhoppers were caged on alfalfa regrowth to feed sequentially through nymphal development and early adulthood. A negative correlation existed between potato leafhopper density and the alfalfa growth parameters measured. Relationships were curvilinear. Correlation was highest between reduction in percent crude protein and potato leafhopper density. Damage was generally more severe on second- than on third-harvest alfalfa. Variability in damage between harvests was, in part, due to a crop effect. Plant height was reduced by 10.7–53.6% when one and eight potato leafhopper nymphs, respectively, attacked an alfalfa stem. Alfalfa dry weight declined 7.3 and 56.6% and crude protein declined 6.2 and 29.5% under these respective potato leafhopper densities. Damage per insect was maximum at one potato leafhopper per stem. Total protein yield per hectare was the most severely reduced parameter. Leaf to stem ratio shifted in favor of leaf development in alfalfa stressed by potato leafhopper nymphs.