Utility of Harvest Weed Seed Control for Italian Ryegrass Management in Wheat

increases in infestations across the state. This weed species has proved to be the most problematic weed for Kentucky wheat growers with our previous research identifying multiple populations of glyphosate-resistant, pinoxaden (Axial XL), and pinoxaden plus fenoxaprop (Axial Bold) resistant annual ryegrass in Kentucky wheat fields. The continued increase and spread of herbicide resistance in ryegrass is inevitable within Kentucky wheat acres as many farmer rely heavily on the pinoxaden based herbicides for postemergence control of ryegrass. The lack of potential postemergence herbicides in the very near future and limitations of currently effective preemergence herbicides call for additional control tactics such as harvest weed seed control at harvest. Rigid ryegrass seed destruction at harvest has been implemented by Australian farmers for over a decade with much success. Previous work supported by the Kentucky Small Grain Growers Association has shown the potential for harvest weed seed control tactics with the majority of ryegrass seed being retained on the ryegrass seed head at harvest and minimal seed shatter at the combine header when infestations are at least partially controlled with a herbicide program. The next step in this research is to investigate the actual use of harvest weed seed control practices for their utility in Kentucky wheat acres. Objectives: 1. Investigate the utility of a Redekop Seed Control Unit installed on a commercial John Deere combine for management of Italian ryegrass in wheat 2. Investigate the utility of chaff lining practices and implementation for management of Italian ryegrass in wheat Research Methods: Objective 1: A Redekop Seed Control Unit (SCU) was purchased and installed on a famer owned John Deere S780 in May of 2022. Replicated 1-acre blocks containing ryegrass infestations were setup in the fall of 2021 and were harvested with and without the SCU engaged. Collections of header shatter, chaff (both straw and fine chaff), and grain samples were collected to evaluate ryegrass seed distribution back into the soil seed bank. Collection will be processed to capture the number viable ryegrass seeds within each collection site throughout the fall of 2022. The study will be repeated in the 2022-23 growing season as well. Objective 2: Chaff lining is the practice of funneling all the fine chaff portion into a concentrated row to create an environment not conducive to growth of weed seeds contained within the fine chaff. Alternatively, chaff lining can also concentrate weed seed to enable target herbicide applications for species that do emerge from within the chaff line. This practice has been adopted in other areas facing herbicide resistant weeds and can be implemented a reduce cost as compared to purchasing an SCU. The goal of this research is to investigate the use of chaff lining at wheat harvest to manage ryegrass populations. Chaff lines were created during the 2022 wheat harvest using fine chaff from research plots with heavy ryegrass infestations. Chaff line efficacy will be evaluated under the influence of chaff line placement and double crop soybean planting. Chaff lines will be either aligned with the wheat rows (or within the combine tire track) and across the wheat row stubble. Double crop soybean will then be planted either across the chaff lines (causing disruption) or with the chaff lines. Chaff lines will be evaluated for ryegrass emergence in the fall of 2022 and spring of 2023 prior to corn planting. Ryegrass seed will also be evaluated for seed viability following set exposure times within the chaff lines. Budget: This research is projected to cost approximately $13,740 which will include salary for Hayden Love (graduate student) who will be primarily responsible for initiating this research and conducting all analysis of samples.