**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** HOST PLANT RESISTANT (HPR) CROPS PROVIDE AN EFFECTIVE AND SUSTAINABLE FORM OF INSECT PEST MANAGEMENT. YET, SOME INSECTS HAVE ADAPTED TO OVERCOME THESE DEFENSES (I.E. VIRULENCE), THREATENING THE EFFICACY OF HPR CROP CULTIVARS. ABIOTIC STRESSORS ASSOCIATED WITH GLOBAL CLIMATE CHANGE MAY ALSO IMPACT HPR TRAIT EXPRESSION, WHICH POTENTIALLY INTRODUCES A SELECTIVE PRESSURE ONTO VIRULENT AND AVIRULENT INSECT POPULATIONS. USING SOYBEANS AND SOYBEAN APHIDS AS A MODEL SYSTEM, THIS PROJECT TAKES A COMBINED EXPERIMENTAL AND MATHEMATIC APPROACH TO QUANTITY HOW WATER STRESS ALTERS VIRULENT AND AVIRULENT APHID POPULATION DYNAMICS. SPECIFIC AIMS INCLUDE COMPARING THE EFFECT OF HOST PLANT WATER STRESS ON VIRULENT AND AVIRULENT FITNESS (OBJ. 1) AND APHID INTERACTIONS WITH A PARASITOID WASP (OBJ. 2). WE ALSO WILL TRACK CHANGES IN THE RELATIVE FREQUENCY OF VIRULENT AND AVIRULENT APHIDS UNDER DIFFERENT WATER STRESS SCENARIOS USING BOTH LABORATORY MESOCOSMS (OBJ. 3) AND QUANTITATIVE MODELING (OBJ. 4), WHICH WILL ALLOW US TO SIMULATE CHANGES IN APHID POPULATIONS IN RESPONSE TO A WIDER ARRAY OF BIOTIC AND ABIOTIC VARIABLES OVER THE COURSE OF A GROWING SEASON. UNDERSTANDING THESE PROCESSES WILL ADVANCE CLIMATE-RESILIENT, INTEGRATED RESISTANCE MANAGEMENT PROGRAMS THAT ENSURE HPR DURABILITY.