Suppression of Microdochium Patch on Annual Bluegrass Putting Greens using Iron Sulfate, Phosphorous Acid, Sulfur, and Mineral Oil

Managing Microdochium patch on intensively manicured annual bluegrass putting greens is a challenge for turfgrass professionals in cool-humid climates similar to the Pacific Northwest. Fungicides are the predominant means to mitigate damage caused by this fungal pathogen, however pesticide restrictions are making it even more challenging to suppress Microdochium patch. Five field experiments, two growth chamber experiments, and two in vitro experiments were carried out to explore the use of iron sulfate heptahydrate, phosphorous acid, sulfur, and mineral oil on the suppression of Microdochium patch and on turfgrass quality. Mineral oil combined with either sulfur or phosphorous acid suppressed Microdochium patch, although combinations of mineral oil and sulfur reduced turfgrass quality, especially in the winter months. This reduction provides evidence that mineral oil and sulfur combinations should be avoided under similar conditions. Eliminating mineral oil applications in the winter months and replacing these applications with a sulfur and phosphorous acid combination suppressed Microdochium patch and mitigated damage although a temporary loss of turfgrass quality was still observed. Applying iron sulfate heptahydrate every two weeks suppressed Microdochium patch but resulted in suboptimal turfgrass thinning. Increasing the application interval of iron sulfate heptahydrate beyond two weeks decreased the level of Microdochium patch suppression observed. Increasing the water carrier volume of iron sulfate heptahydrate applications resulted in less abiotic damage quantified by having higher green cover percentages and these higher carrier volumes did not have a negative impact on Microdochium patch suppression. No benefit in Microdochium patch suppression was observed when adding iron sulfate heptahydrate to phosphorous acid applications compared to phosphorous applications alone, although turfgrass quality was improved when phosphorous acid was used in combination with some rates of iron sulfate heptahydrate. Both iron sulfate heptahydrate and phosphorous acid applications reduced the turfgrass surface pH for up to 17 days post application. Subsequent growth chamber and in vitro studies suggested that a reduction in pH was not solely responsible for the suppression in Microdochium patch by iron sulfate heptahydrate applications. These studies have demonstrated that multiple approaches of suppressing Microdochium patch are available to turfgrass managers and that future research is warranted in using these techniques as a part of an integrated pest management plan

Managing Microdochium Patch Using Non-Traditional Fungicides on Annual Bluegrass Putting Greens

Currently, fungicide applications are the predominant method of control for the cool weather pathogen Microdochium patch (Microdochium nivale). Increasing pesticide restrictions have generated concern regarding management of Microdochium patch. Three separate field trials exploring non-traditional fungicides were conducted between 2013 and 2015 on an annual bluegrass (Poa annua L.) sand-based putting green at the Lewis Brown Horticulture Farm, Corvallis, OR. The objective of the first project was to evaluate the effects of the cultural practice of rolling in combination with mineral oil and fertility on Microdochium patch incidence. The objective of the second trial was to quantify the effects on Microdochium patch incidence using biological control products in combination with rolling. Finally, the objective of the third experiment was to quantify the effects of different nitrogen and iron sulfate rates in combination with simulated golfer traffic on the effects of Microdochium patch incidence as well as turfgrass recuperation. The first experiment determined that rolling in combination with Civitas One or Sulfur DF + PK Plus suppressed disease to levels comparable to traditional fungicides. Civitas One with rolling resulted in abiotic damage. The second experiment determined that rolling as well as the biological control agents BW136N, followed by Rhapsody suppressed Microdochium patch disease. The third experiment determined that 4.88 Kg N ha⁻¹ combined with 97.65 Kg FeSO₄ ha⁻¹ provided the greatest combination of disease control and turf quality

Ethofumesate-resistant annual bluegrass (Poa annua) in grass seed production systems

The prolific seed production and polyploidy of annual bluegrass allow for the rapid development of herbicide resistance. Ethofumesate-resistant annual bluegrass plants were identified in the 1990s in grass seed production in Oregon, but their prevalence and distribution are not well documented. Therefore a dose–response experiment was initiated to determine the potential level of ethofumesate resistance in seed production systems. Seeds from 55 annual bluegrass populations were obtained from three sources: seed production fields (31 populations), the seed cleaning process (6 populations), and seed testing lots prior to retail distribution (18 populations). Additionally, two populations, one with known ethofumesate resistance and one with known susceptibility, were identified in preliminary testing and used as controls in this experiment. Seed from each collected population was increased. Individual seedlings were then transplanted into separate cone-tainers, grown to a size of 2 to 3 tillers in the greenhouse, and then sprayed using a compressed air track spray chamber with 10 doses of ethofumesate at 0, 0.56, 1.1, 2.8, 5.6, 8.4, 11.2, 16.8, 22.4, and 44.8 kg ai ha−1, with 0.84 to 2.2 kg ha−1 as the label application rate for perennial ryegrass. The resistant to susceptible ratio of populations across all sources ranged from 0.5 to 5.5. The most resistant populations found in production fields, seed cleaning, and seed testing lots had the effective dose necessary to kill 50% of the population (ED50) of 12.1, 9.4, and 13.1 kg ha−1, respectively. Furthermore, 68% of the populations found in production fields had ED50 higher than 6 kg ha−1, indicating common annual bluegrass resistance in grass seed production. As such, growers should implement integrated weed management strategies, as herbicides alone will likely be ineffective at controlling annual bluegrass

Agricultural Research Service Weed Science Research: Past, Present, and Future

The U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) has been a leader in weed science research covering topics ranging from the development and use of integrated weed management (IWM) tactics to basic mechanistic studies, including biotic resistance of desirable plant communities and herbicide resistance. ARS weed scientists have worked in agricultural and natural ecosystems, including agronomic and horticultural crops, pastures, forests, wild lands, aquatic habitats, wetlands, and riparian areas. Through strong partnerships with academia, state agencies, private industry, and numerous federal programs, ARS weed scientists have made contributions to discoveries in the newest fields of robotics and genetics, as well as the traditional and fundamental subjects of weed-crop competition and physiology and integration of weed control tactics and practices. Weed science at ARS is often overshadowed by other research topics; thus, few are aware of the long history of ARS weed science and its important contributions. This review is the result of a symposium held at the Weed Science Society of America\u27s 62nd Annual Meeting in 2022 that included 10 separate presentations in a virtual Weed Science Webinar Series. The overarching themes of management tactics (IWM, biological control, and automation), basic mechanisms (competition, invasive plant genetics, and herbicide resistance), and ecosystem impacts (invasive plant spread, climate change, conservation, and restoration) represent core ARS weed science research that is dynamic and efficacious and has been a significant component of the agency\u27s national and international efforts. This review highlights current studies and future directions that exemplify the science and collaborative relationships both within and outside ARS. Given the constraints of weeds and invasive plants on all aspects of food, feed, and fiber systems, there is an acknowledged need to face new challenges, including agriculture and natural resources sustainability, economic resilience and reliability, and societal health and well-being

Carbon Sequestration in Turfgrass–Soil Systems

Plants are key components of the terrestrial ecosystem carbon cycle. Atmospheric CO2 is assimilated through photosynthesis and stored in plant biomass and in the soil. The use of turfgrass is expanding due to the increasing human population and urbanization. In this review, we summarize recent carbon sequestration research in turfgrass and compare turfgrass systems to other plant systems. The soil organic carbon (SOC) stored in turfgrass systems is comparable to that in other natural and agricultural systems. Turfgrass systems are generally carbon-neutral or carbon sinks, with the exception of intensively managed areas, such as golf course greens and athletic fields. Turfgrass used in other areas, such as golf course fairways and roughs, parks, and home lawns, has the potential to contribute to carbon sequestration if proper management practices are implemented. High management inputs can increase the biomass productivity of turfgrass but do not guarantee higher SOC compared to low management inputs. Additionally, choosing the appropriate turfgrass species that are well adapted to the local climate and tolerant to stresses can maximize CO2 assimilation and biomass productivity, although other factors, such as soil respiration, can considerably affect SOC. Future research is needed to document the complete carbon footprint, as well as to identify best management practices and appropriate turfgrass species to enhance carbon sequestration in turfgrass systems