PROBLEM AND BACKGROUNDHERBICIDES REMAIN THE CORNERSTONE OF EFFECTIVE WEED MANAGEMENT IN BROAD-ACRE FARMING, BUT OVER-RELIANCE ON FEW HERBICIDE OPTIONS HAS RESULTED IN THE EVOLUTION OF HERBICIDE-RESISTANT WEEDS. IN THE SOUTHERN US, HERBICIDE-RESISTANT WEEDS HAVE BECOME A CRITICAL CROP PRODUCTION CHALLENGE IN RECENT TIMES (RIAR ET AL. 2013A). MULTIPLE RESISTANCE TO MORE THAN ONE HERBICIDE SITE OF ACTION (SOA) IS PARTICULARLY A GROWING CONCERN IN THE REGION. PALMER AMARANTH (AMARANTHUS PALMERI S. WATS.) AND WATERHEMP (AMARANTHUS TUBERCULATUS MOQ.) (A WEED SIMILAR TO PALMER AMARANTH IN ITS BIOLOGY) ARE TWO MAJOR RESISTANCE-PRONE BROADLEAF WEED SPECIES IN THE AGRONOMIC CROP-PRODUCTION SYSTEMS OF THE SOUTHERN AND MID-WESTERN US, WHEREAS BARNYARDGRASS (ECHINOCHLOA CRUS-GALLI L.) IS AN IMPORTANT GRASS WEED WITH HIGH POTENTIAL FOR EVOLVING HERBICIDE RESISTANCE IN THESE SYSTEMS (HEAP 2019). MULTIPLE HERBICIDE RESISTANCE IN PALMER AMARANTH (SOSNOSKIE ET AL. 2011), WATERHEMP (SHERGILL ET AL. 2018), AND BARNYARDGRASS (TALBERT AND BURGOS 2007; LIU ET AL. 2017) HAS BEEN CAUSING SERIOUS ECONOMIC AND ENVIRONMENTAL DAMAGES.IMPORTANCE OF A PROACTIVE, IPM APPROACH TO TACKLING THE PROBLEMWHEN LOOKING AT HOW HERBICIDE RESISTANCE IN WEEDS HAS BEEN DEALT WITH THUS FAR, IT IS MORE OFTEN REACTIVE RATHER THAN PROACTIVE. A REACTIVE APPROACH ATTEMPTS TO MANAGE RESISTANCE AFTER RESISTANCE HAS ALREADY EVOLVED, WHEREAS A PROACTIVE APPROACH IS GEARED TOWARDS PREVENTING RESISTANCE FROM APPEARING IN THE FIRST PLACE (MUELLER ET AL. 2005). A PROACTIVE APPROACH ADVOCATES MORE DIVERSIFIED MANAGEMENT OPTIONS RIGHT FROM THE START. SOIL WEED SEEDBANK MANAGEMENT IS AN IMPORTANT ELEMENT OF PROACTIVE RESISTANCE MANAGEMENT. SIMULATION MODELS HAVE EMPHASIZED THAT THE RISK OF HERBICIDE RESISTANCE IS STRONGLY AND POSITIVELY ASSOCIATED WITH SOIL SEEDBANK SIZE (BAGAVATHIANNAN ET AL. 2013; NEVE ET AL. 2011). TRADITIONAL WEED CONTROL RECOMMENDATIONS WERE BASED ON AN ECONOMIC THRESHOLD (ET) CONCEPT, WHICH ADVOCATES CONTROL WHEN WEED DENSITIES EXCEED A YIELD LOSS THRESHOLD. HOWEVER, THE ET CONCEPT DOES NOT ADEQUATELY ADDRESS THE LIKELIHOOD OF WEED SEEDBANK ADDITION, WHICH MIGHT INCREASE FUTURE WEED MANAGEMENT COSTS AND ALSO ELEVATE THE RISK OF RESISTANCE EVOLUTION (NORRIS 1999; BAGAVATHIANNAN AND NORSWORTHY 2012). THEREFORE, A PROACTIVE APPROACH TO RESISTANCE MANAGEMENT REQUIRES A STRONG FOCUS ON MINIMIZING SOIL WEED SEEDBANK LEVELS.OBSTACLES TO IPM ADOPTIONBEST MANAGEMENT PRACTICES (BMPS) BASED ON AN IPM APPROACH TO HERBICIDE RESISTANCE MANAGEMENT HAVE BEEN DEVELOPED WITH COLLABORATIVE EFFORTS BETWEEN USDA-APHIS AND WEED SCIENCE SOCIETY OF AMERICA, UTILIZING THE KNOWLEDGE GAINED FROM A WEALTH OF RESEARCH ACTIVITIES CONCERNING THIS ISSUE (NORSWORTHY ET AL. 2012). THE LEVEL OF ADOPTION OF THE BMPS, HOWEVER, HAS BEEN SLOW. A SURVEY BY RIAR ET AL. (2013B) INDICATED THAT ONE OF THE MAJOR CONSTRAINTS TO BMP ADOPTION BY GROWERS IS THE FAILURE TO RECOGNIZE THE LONG-TERM BENEFITS OF BMP ADOPTION. CONVINCING GROWERS OF THE ECONOMICAL COMPETENCE OF A PROACTIVE, IPM APPROACH TO HERBICIDE RESISTANCE MANAGEMENT REMAINS A SIGNIFICANT CHALLENGE. A NUMBER OF BMPS FOR THE MANAGEMENT OF HERBICIDE RESISTANCE IN PALMER AMARANTH (NEVE ET AL. 2011) AND BARNYARDGRASS (BAGAVATHIANNAN ET AL. 2013) WERE DEVELOPED WITH GUIDANCE FROM SIMULATION MODELING EFFORTS, BUT THESE MODELS WERE ONLY INTENDED AS RESEARCH TOOLS AND ARE NOT SUITABLE FOR USE AS DECISION-AID TOOLS IN EXTENSION ACTIVITIES. THE LACK OF AN EFFECTIVE, USER-FRIENDLY, EDUCATION/EXTENSION TOOL TO DEMONSTRATE THE LONG-TERM BIOLOGICAL AND ECONOMIC VIABILITY OF IPM STRATEGIES REPRESENTS A SUBSTANTIAL LIMITATION TO THE PROMOTION OF IPM TACTICS BY EXTENSION PERSONNEL.PAM: A BIO-ECONOMIC MODEL TO GUIDE PALMER AMARANTH MANAGEMENTWITH THE NEED FOR AN EFFECTIVE DECISION-SUPPORT TOOL TO ASSIST THE DISSEMINATION OF IPM TACTICS BY EXTENSION PERSONNEL, OUR TEAM HAS DEVELOPED A MICROSOFT EXCEL&TRADE; BASED TOOL, KNOWN AS THE PALMER AMARANTH INTEGRATED MANAGEMENT (PAM) MODEL. THIS TOOL HAS BEEN EFFECTIVE FOR DEMONSTRATING THE LONG-TERM BIOLOGICAL AND ECONOMIC BENEFITS OF ADOPTING INTEGRATED STRATEGIES FOR PALMER AMARANTH MANAGEMENT (LINDSAY ET AL. 2017). THE MODEL SIMULATES LONG-TERM (10 YEAR) AVERAGE ECONOMIC RETURNS AS WELL AS THE SEEDBANK SIZE OF PALMER AMARANTH. IT ALLOWS THE USER TO BUILD VARIOUS CROP ROTATION AND WEED MANAGEMENT STRATEGIES FOR A 10-YEAR PERIOD AND SEE FOR THEMSELVES THE ECONOMIC AND BIOLOGICAL BENEFITS OF USING, OR DRAWBACKS OF NOT USING, A DIVERSIFIED IPM STRATEGY TO WEED MANAGEMENT. SPECIFIC NON-CHEMICAL OPTIONS INCORPORATED IN THE MODEL INCLUDE CROP ROTATION, ROW SPACING, COVER CROPS, SEEDBED PREPARATION, MOLDBOARD PLOWING AND HARVEST-TIME WEED SEED CONTROL, AMONG OTHERS. THIS TOOL ALSO INCLUDES A RESISTANCE RISK CALCULATOR THAT AUTOMATICALLY DISPLAYS THE RISK OF HERBICIDE RESISTANCE TO THE HOST OF MANAGEMENT OPTIONS SELECTED BY THE USER. THE PAM MODEL WAS DEVELOPED BASED ON CONSTANT FEEDBACK PROVIDED BY END USERS.THE PAM MODEL IS CURRENTLY AVAILABLE FOR DOWNLOAD AT HTTP://AGRIBUSINESS.UARK.EDU/DECISION-SUPPORT-SOFTWARE.PHP#PAM. THIS TOOL HAS BEEN WIDELY CIRCULATED THROUGH VARIOUS OUTREACH OUTLETS AND IS CURRENTLY USED IN EXTENSION ACTIVITIES. THE MAJOR TARGET AUDIENCE FOR THIS TOOL IS CROP CONSULTANTS AND EXTENSION PERSONNEL, WHO RUN VARIOUS SCENARIOS AND USE THE INFORMATION IN THEIR WEED MANAGEMENT PLANNING AND OUTREACH ACTIVITIES, WHILE SOME PROGRESSIVE FARMERS ALSO USE THIS BY THEMSELVES. A NUMBER OF WEED MANAGEMENT AND CROP PRODUCTION SCENARIOS CAN BE SIMULATED BY THE SOFTWARE AND THE OUTPUTS CAN BE USED TO DEMONSTRATE THE LONG-TERM BENEFITS OF DIVERSIFIED WEED MANAGEMENT.THE PLANTHE FOCUS OF THIS PROPOSAL IS TO IMPROVE THE PAM MODEL TO PROVIDE SYSTEM-BASED HERBICIDE RESISTANCE MANAGEMENT EDUCATION AND TO EXPAND ITS APPLICATION TO THE MID-WESTERN US. AS MENTIONED EARLIER, BARNYARDGRASS IS A DOMINANT GRASS WEED IN VARIOUS AGRONOMIC CROP PRODUCTION SYSTEMS ACROSS THE SOUTHERN AND MID-WESTERNUS. IT IS THE SECOND MOST IMPORTANT WEED SPECIES GLOBALLY THAT SHOWS HIGH-RISK FOR THE EVOLUTION OF HERBICIDE RESISTANCE, WITH RESISTANCE TO AT LEAST 10 DIFFERENT HERBICIDE SOA AS OF TODAY (HEAP 2019). THE PAM MODEL WILL BE REVISED AND IMPROVED TO INCLUDE WATERHEMP AND BARNYARDGRASS. FURTHER, THESE IMPROVEMENTS WILL BE IMPLEMENTED IN A WEBSITE INTERFACE TO ACHIEVE WIDER ACCESSIBILITY AND UTILIZATION. IT IS ANTICIPATED THAT SUCH IMPROVEMENTS WILL MAKE THIS A ROBUST-DECISION SUPPORT TOOL TO PROMOTE IPM-BASED STRATEGIES FOR HERBICIDE RESISTANCE MANAGEMENT.THE SHORT-TERM GOAL OF THIS PROJECT IS TO DEVELOP AND DELIVER A ROBUST SYSTEM-BASED DECISION-SUPPORT TOOL FOR DEMONSTRATING TO CONSULTANTS, DEALERS, DISTRIBUTORS, EXTENSION PERSONNEL AND GROWERS, THE BENEFITS OF ADOPTING AND THE PENALTIES OF NOT ADOPTING IPM TACTICS FOR HERBICIDE RESISTANCE MANAGEMENT ENCOMPASSING BOTH GRASS AND BROADLEAF WEEDS. THE LONG-TERM GOAL OF THE PROJECT IS TO DEMONSTRATE TO THE CLIENTELE THE VALUE OF SYSTEM-BASED IPM APPROACHES TO WEED MANAGEMENT AND THEREBY MINIMIZE THE ECONOMIC, HUMAN HEALTH, AND ENVIRONMENTAL IMPACTS ASSOCIATED WITH WEED MANAGEMENT IN GENERAL AND HERBICIDE RESISTANCE IN PARTICULAR.