EVALUATING THE EFFECT OF POTATO LEAFHOPPER (EMPOASCA FABAE) FEEDING ON BIOLOGICAL NITROGEN FIXATION IN ALFALFA (MEDICAGO SATIVA)

Abstract

Aboveground feeding by potato leafhopper (PLH), Empoasca fabae, (Hemiptera: Cicadellidae) causes significant injury to alfalfa (Medicago sativa), including disrupting translocation of fixed carbon from leaves to roots. Basal transport of fixed carbon in alfalfa fuels a critical mutualism between roots and nitrogen-fixing bacteria (Sinorhizobium meliloti). Above- and belowground nutrient allocation in alfalfa determines perennial persistence across growing seasons, as well as forage quality. Whether leafhopper feeding alters nutrient allocation and subsequently affects nitrogen fixation, however, is not clear. To test this, my objectives were 1) to examine the effect of different management strategies on PLH injury and nitrogen fixation, and 2) to quantify the amount and location of fixed nitrogen in whole alfalfa plants when fed on by leafhoppers. Overall, my work contributes to an understanding of how aboveground pest pressure can disrupt belowground processes in plants and ultimately affect the economic viability of crops for growers.