MOST PLANT VIRUSES ARE VECTORED BY INSECTS. VIRUS INFECTION CAN ALTER VECTOR ABUNDANCE AND BEHAVIOR, POTENTIALLY PROMOTING VIRUS SPREAD. HOWEVER, UNDER FIELD CONDITIONS, PLANTS ALSO EXPERIENCE DAMAGE FROM NON-VECTOR INSECTS. SUCH HERBIVORY MAY ALTER VECTOR-PLANT-VIRUS DYNAMICS AND IMPACT DISEASE SPREAD. CONSISTENT WITH THIS HYPOTHESIS, WE HAVE FOUND THAT THE SPREAD OF PEA ENATION MOSAIC VIRUS (PEMV), A DEVASTATING VIRUS AFFECTING LEGUMES, IS IMPACTED BY HERBIVORY FROM THE PEA LEAF WEEVIL (PLW). PEMV IS PRIMARILY VECTORED BY THE PEA APHID, AND APHIDS INFECTED WITH PEMV HAVE HIGHER FITNESS, BUT DECREASED MOVEMENT, ON PLW DAMAGED PLANTS. MOREOVER, PLANTS DAMAGED BY PLW ARE MORE SUSCEPTIBLE TO PEMV. BECAUSE HERBIVORY BY PLWS ALTERS VECTOR FITNESS, BEHAVIOR, AND PLANT SUSCEPTIBILITY, VARIATION IN PLW HERBIVORY IN COMMERCIAL FIELDS MAY IMPACT PEA APHID OUTBREAKS AND INCIDENCE OF PEMV. OUR PROJECT WILL INVESTIGATE MECHANISMS UNDERLYING EFFECTS OF PLW HERBIVORY ON PEMV-APHID-PLANT INTERACTIONS AND VARIATION IN INCIDENCE OF PEMV IN THE FIELD. SPECIFICALLY, THE OBJECTIVES OF THIS PROJECT ARE: (1) EVALUATE HOW HERBIVORY AFFECTS THE SUSCEPTIBILITY OF PLANTS TO PEMV AND THE FUNCTION OF PLANTS AS DISEASE RESERVOIRS; (2) EXPLORE HOW HERBIVORY AND PEMV AFFECT VECTOR FITNESS AND BEHAVIOR; AND (3) INVESTIGATE HOW HERBIVORY AFFECTS INCIDENCE OF PEMV IN THE FIELD. OUR PROJECT ADDRESSES THREE PRIORITIES OF THE PESTS AND BENEFICIAL SPECIES IN AGRICULTURAL PRODUCTION SYSTEMS PROGRAM: (1) INTERACTIONS OF PESTS WITH PLANT COMPOUNDS, GENES, OR STRESSORS; (2) EFFECTS OF DEFENSE SIGNALING SYSTEMS ON PESTS; AND (3) UNDERSTANDING MOVEMENT OF PESTS, INCLUDING PESTS THAT VECTOR PLANT DISEASES. OUR PROJECT WILL PROVIDE NOVEL INSIGHT INTO HOW INTERACTIONS BETWEEN PLANTS, INSECTS, AND PATHOGENS AFFECT DISEASE SPREAD, GENERATING RESULTS OF IMMEDIATE RELEVANCE FOR MANAGEMENT OF PEMV AND OTHER VIRUSES.