ECOLOGY AND CONTROL OF ANNUAL WEEDS IN TURFGRASS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1013421
• Project Start Date: Aug 18, 2017
• Project End Date: Jul 31, 2022
• Program Code: [(N/A)]- (N/A)

Recipient Organization
RUTGERS, THE STATE UNIVERSITY OF NEW JERSEY
3 RUTGERS PLZA
NEW BRUNSWICK,NJ 08901-8559

Performing Department
Plant Biology

Non Technical Summary
Annual bluegrass (Poa annua L.) is one of the most problematic weeds of turfgrass in New Jersey and around the world, especially on golf courses and athletic fields. Infested parks, athletic fields, and golf courses often exhibit poor playing quality during hot and dry conditions in the summer unless substantial pesticide and irrigation inputs are used. Turfgrass systems infested with annual bluegrass are less economical and require more inputs than systems with desirable turfgrass species such as creeping bentgrass,Kentucky bluegrass or tall fescue. Crabgrass (Digitaria spp.) is another common annual weed that invades lawns, athletic fields and golf courses across the United States. Crabgrass reduces the functional and aesthetic quality of turfgrass, particularly in the fall and winter after it completes its life cycle and dead plants leave large voids in the turfgrass. Lawns, parksand athletic fields infested with crabgrass wear out quickly and produce a muddy field prone to soil erosion.Herbicides can be used for annual bluegrass control but they often cause injury to desirable turfgrass and provide annual bluegrass control that is inconsistent and often too rapid, creating large voids in the turfgrass canopy. Non-chemical methods can aid in preventing annual bluegrass establishment but are largely ineffective in controlling established annul bluegrass. Crabgrass control programs used by professionals and homeowners rely extensively on herbicides; multiple herbicide applications are often required to provide acceptable crabgrass control even when used in conjunction with proper cultural practices to promote desirable turfgrass growth. Effective alternatives to synthetic herbicides that involve cultural practices and non-synthetic herbicides need to be developed. Research to better understand factors contributing to infestations of annual bluegrass and crabgrass would aid the development of these alternatives and help improve cultural practices to complement both synthetic and non-synthetic herbicides.In addition to investigating applied approaches for weed control, we will also investigate microbes that may enhance the competitiveness of crabgrass. It is generally accepted that communities of bacteria and fungi inhabit plants as endophytes, meaning they colonize plant tissues. In most cases these bacteria and fungi do not cause disease and have been shown to increase the fitness of plant hosts. The microbial endophytes of crabgrass have hardly been researched. This research will explore seed-associated endophytes of crabgrass and attempt to elucidate their affect on the fitness of these weedsThis project will investigate low environmental impact alternatives to synthetic herbicides and how they can be used in concert with cultural practices to control weeds that are extremely problematic across the northern United States. Initially, these synthetic herbicide alternatives and cultural practices will be evaluated as separate components to understand their influence on weeds. To combine these components into an integrated system for weed control, components determined with weed control efficacy or influence on weed invasion will be combined and investigated in various systems for weed control. This research will hopefully develop improved integrated approaches to manage these problematic weeds on home lawns, athletic fields and golf courses with fewer pesticide inputs.

Animal Health Component

80%

Research Effort Categories

Basic

20%

Applied

80%

Developmental

0%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
216	2130	1140	100%

Knowledge Area
216 - Integrated Pest Management Systems;

Subject Of Investigation
2130 - Turf;

Field Of Science
1140 - Weed science;

Keywords

weeds

biocontrol

endophytes

turfgrass

Goals / Objectives
This project will investigate low environmental impact alternatives to synthetic herbicides and how they can be used in concert with cultural practices to control weeds that are extremely problematic across the northern United States. Initially, these synthetic herbicide alternatives and cultural practices will be evaluated as separate components to understand their influence on weeds. To combine these components into an integrated system for weed control, components determined to have weed control efficacy or influence on weed invasion will be combined and investigated in various systems for weed control. This research will hopefully develop improved integrated approaches to manage these problematic weeds.

Project Methods
Objective One: Determine if annual bluegrass weevil can be used as a biological control of annual bluegrass on golf course fairways in combination with other management practices.This research will be conducted at the Rutgers Horticultural Research Farm No. 2 and on two New Jersey golf course fairways. We will investigate three annual bluegrass weevil control regimens alone and in combination with a plant growth regulator and interseeding program for annual bluegrass control in a mixed creeping bentgrass annual bluegrass fairway. The details of each of these components are outlined below.Three Annual Bluegrass Weevil Control Programs: The first annual bluegrass weevil program is designed to completely prevent annual bluegrass weevil damage by controlling early- and late-instar larvae using an industry standard insecticide-based control program. The second program will allow first generation annual bluegrass weevil larvae to develop and cause annual bluegrass damage before an insecticide application. The field plots will be monitored closely to determine when annual bluegrass weevil damage results in marginally acceptable turfgrass quality, at which time insecticides will be applied to halt further turf damage. Additional insecticides will be applied to control second and third generation annual bluegrass weevil larvae for the rest of the growing season in these plots if damage is observed. The third program will not use any insecticide for annual bluegrass weevil control.Interseeding: Plots with different annual bluegrass weevil management programs will be divided into sub plots to evaluate the effects of '007' creeping bentgrass interseeding compared to no interseeding. To maximize the competitive advantage of creeping bentgrass seedlings, interseeding will occur approximately 1 week after whole plots in the second annual bluegrass weevil program cross the damage threshold, likely in early June.PGR Program: Sub plots with annual bluegrass weevil management programs and interseeding will be divided again into sub-sub plots to evaluate these strategies in combination with a paclobutrazol plant growth regulator program that involves monthly applications from April to October.Objective Two: Identify bacterial and fungal isolates of smooth crabgrass and annual bluegrass seed that are endophytic and determine their influence on weediness.We have isolated bacteria and fungi that vector on or within smooth crabgrass (Digitaria ischaemum (Schreb.) Schreb. ex Muhl.) and annual bluegrass (Poa annua L.) seed by surface disinfecting seeds in 4% sodium hypochlorite for 40 min. to remove all surface and placing into bacterial culture media as above to isolate cultivable species. We have obtained nine isolates from annual bluegrass and 17 from smooth crabgrass. We have also identified a Curvularia spp. fungus that may be endophytic to smooth crabgrass seed. We will evaluate the effect of these isolates on smooth crabgrass and annual bluegrass as well as common weeds of turfgrass and cropping systems. We hypothesize that some of these bacteria that become will become intracellular and increase fitness of smooth crabgrass and annual bluegrass. We also hypothesize that some of these bacteria will decrease fitness of competitor species. Weed-isolate interactions will be evaluated through a graduated screening process consisting of the following methods.Plate BioassayTo better understand the weed control spectrum and effects on cultivated turfgrasses, the aforementioned bacterial isolates will be evaluated with various plant species.Each experimental unit will consist of one 100 x 15-mm petri dish filled with sterile water agar (0.7%). One mL of mid-log culture will be dispensed onto the water agar and allowed to absorb into the agar for 3 to 4 hours. Ten surface sterilized seeds of each target weed or cultivated turfgrass will be placed onto the agar surface and incubated at 15 °C under ambient light for an appropriate period of time to allow for germination and root/shoot growth. After the appropriate period, mortality will be determined and the longest root on each plant will be measured. Each treatment will be replicated ten times and the experiment will be repeated in time.Whole Plant AssayBased on the results of the first screen, certain isolate x weed combinations will be evaluated further on whole plants. Two sterilized seeds will be planted to into Magenta boxes (77mm × 77mm × 97mm) filled to a 20 mm depth with sterilized peat-based growing media. After dicots accumulate at least 4 true leaves and monocots reach the two-tiller stage, the boxes will be inoculated with the appropriate bacterial isolate by dispensing 5 mL of mid-log culture onto the growing media. After the appropriate period, mortality will be determined and the longest root, on each plant will be measured. Each treatment will be replicated ten times and the experiment will be repeated in time. Comparisons will be made to a control treated with sterile media.Greenhouse ScreenBased on the results of the first and second screen, certain isolate x weed combinations will be evaluated further on weeds and desirable turfgrass planted in non-sterilized sandy loam field soil in a greenhouse to evaluate pre- and post-emergence efficacy of certain isolates. Seeds will be planted to one half of a seed tray (165 x 100 x 50 mm) filled with soil and allowed to grow until dicots accumulate at least 4 true leaves and monocots reach the two-tiller stage. Plants will be thinned so that only 5 plants are present at the time of treatment. Another set of seeds will be planted 24 hours prior to treatment application to evaluate pre-emergence control. Bacterial isolates will be applied by dispensing 20 mL of mid-log culture to each tray. Weed control will be evaluated visually compared to a non-treated control. To provide a quantitative assessment of post-emergence treatments, the plants in each tray will be harvested and the roots and shoots will be separated. The roots will be washed free of soil, dried at 60°C for 48 hours and weighed. Shoots will be dried similarly and weighed. Root and shoot weights will be compared to the non-treated control to determine percent reduction for each treatment.Objective Three: Evaluate the effect of certain cultural practices on weed encroachment in turfgrass.We will evaluate the effect of aerification timing on crabgrass cover in a simulated lawn. This is a two-year experiment; treatments will be applied in 2017 and responses will be evaluated in 2017 and 2018. This experiment will be conducted at Rutgers Horticulture Farm No. 2. Collaborators at Iowa State University, Kansas State University and the University of Nebraska will also conduct this experiment. We hypothesize that core cultivating in the fall will not increase crabgrass cover relative to the non-treated control but spring core-cultivation will. Plots sized 10' by 15' with a low to moderate infestation of crabgrass the previous year will be used for the experiment.Objective Four: Develop integrated approaches that use biological, cultural, and chemical management to control crabgrass and annual bluegrass in an economical program that can be utilized by stakeholders.The exact methods of these experiments will not be finalized until the third year of this project. We will develop multi-year field experiments that integrate significant findings of objectives one, two, and three into traditional management programs to determine how suitable they are for use by stakeholders. These new approaches will displace certain components of a traditional management program. We will conduct these trials using larger plots with weed densities more commonly observed in turfgrass systems. This is more likely to elucidate smaller effect sizes associated with alternative practices over a multi-year experiment.

Progress 10/01/19 to 09/30/20

Outputs
Target Audience:Other scientists and industry professionals. Changes/Problems:Extension activites were limited with no in person meetings or field days. Many online meetings have replaced them, but this format limits the scope of work to present. What opportunities for training and professional development has the project provided?Graduate student Katherine Diehl was responsible for various projects to understand whether annual bluegrass weevil can be used as a biological tool for annual bluegrass control as part of her MS thesis. She successfullydefended her thesis in February 2020. As corresponding author, Katieprepared, submitted, and revised a manuscript based on this research in Crop Science Journal. Postdoctoral research Richard Chen led the work described in Objective 2. Field researcher Dan Tuck is leading the research to better understand chelated iron for crabgrass control. How have the results been disseminated to communities of interest?Two journal articles were submitted and accepted for dissemination in the scientific community. Several abstracts were presented at scientific meetings. Research from Objectives 1 and 2 werepresented at various meetings across the United States to industry professional groups. What do you plan to do during the next reporting period to accomplish the goals?We will initiate greenhouse research to investigate the efficacy of chelated iron for smooth crabgrass control at different growth stages as referenced above. Results discussed in Objective 3 will be submitted for publication. We will initiate field research to further explore the annual bluegrass weevil for annual bluegrass control in golf fairways

Impacts
What was accomplished under these goals? Objective 1: The graduate student working on this objective defended her thesis in February and had the first of two journal articles related to the project accepted in early December. The second article is in preparation. This research found that the annual bluegrass weevil can control annual bluegrass, but that the insect must be allowed to cause severe damage. This is problematic in turfgrass where a significant portion of the sword is composed of annual bluegrass and rapidly killing the annual bluegrass is problematic. We observed this anecdotally in our research when the sward was composed of >50% annual bluegrass. To explore this in more detail a proposal (led by Dr. Koppenhofer in entomology, with my project supporting) was submitted to examine the utility of annual bluegrass weevil for annual bluegrass control in golf fairways that consists of 0, 10, 25 and 50% annual bluegrass. Our objective is to determine if annual bluegrass weevil larvae can be allowed to cause severe annual bluegrass damage in fairways with less annual bluegrass, thus providing better annual bluegrass control. Objective 2: In previous research we determined that annual bluegrass endophytes were not pathogenic to competitor plants. So we sought to determine whether these endophytes might enhance annual bluegrass and contribute to its weediness. Annual bluegrass is a very competitive weed of turfgrass systems across the US. We wanted to determine whether annual bluegrass endophytes are conserved across locations and management inputs (e.g., fertilizer) within these locations. In this study, we conducted metagenomic analyses of microbial communities associated with annual bluegrass seeds from three locations with sandy soils in New Jersey, North Carolina, and Texas. Annual bluegrass plants were collected from adjacent areas with high (i.e., fairways and sod) and low management inputs at each location. Seeds were collected from annual bluegrass plants and surface sterilized or left non-sterilized. The bacterial and fungal communities were characterized. Regardless of locations and seed treatments, the bacterial community associated with annual bluegrass seeds was composed of 13 phyla, 18 classes, 38 orders, 61 families and 100 genera. At genus level, Pantoea (49%) and Pseudomonas (35%) bacteria were the most abundant. Sterilization procedure reduced the diversity of bacterial community associated with NC seeds but not NJ or TX seeds. Sterilization did not affect the diversity of fungal communities on TX samples but reduced the diversity of fungal communities on NJ samples This suggests many bacteria and fungi live inside the seed, possibly to be transferred to the plant seedling. Among the genera we found on/in P. annua seeds, some are known to contain plant-beneficial microbes, e.g. Pantoea, Pseudomonas, Cladosporium, and Aureobasidium. Objective 3. An article detailing this research was accepted for publication in the International Turfgrass Research Journal in 2020, to be published in 2021. Our research efforts on this objective have concluded, but the findings continue to be shared in my Extension outreach teaching Objective 4. Our current research found that annual bluegrass weevil larvae provided selective annual bluegrass control similar to that of plant growth regulator programs currently used by practitioners. Control from annual bluegrass weevil larvae was enhanced further when combined with plant growth regulator programs. This two-strategy approach was extremely effective, so much so that the playability of the turfgrass was compromised when annual bluegrass comprised a significant portion of the sward. The next phase of this research will determine how well this combination approach works in fairways that consist of 0, 10, 25 and 50% annual bluegrass, as mentioned in Objective 1. Other research: Consumer and legislative pressure have increased the demand for natural or low-impact weed control products. Smooth crabgrass is a ubiquitous weed problem of turfgrass systems of which efficacious natural or low-impact control products are limited. Field experiments were conducted to evaluate the efficacy of chelated iron containing herbicides for PRE and POST smooth crabgrass control at various rates, timings, and sequences. Chelated iron is not a traditional synthetic herbicide and can be used as part of a low environmental impact management program. We have found that two applications of chelated iron can suppress crabgrass. In 2020 we investigated two-application programs of chelated beginning June 1, June 15, July 1, or July 15. A preliminary analysis of data suggests that chelated iron is effective when applied in June, but not July once crabgrass growth becomes rapid. Greenhouse research is needed to better understand the influence of crabgrass growth stage on chelated iron efficacy.

Publications

• Type: Journal Articles Status: Published Year Published: 2020 Citation: Diehl, K.H., M.T. Elmore, A.M. Koppenh�fer, J.A. Murphy, O.S. Kostromytska. 2020. Annual bluegrass weevil, paclobutrazol, and overseeding for annual bluegrass control in cool-season turfgrass. Crop Science. https://doi.org/10.1002/csc2.20430
• Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Diehl. K.H., M.T. Elmore, J.A. Murphy, A.M. Koppenh�fer. 2020. Annual bluegrass weevil for annual bluegrass control in fairways. Proceedings of the 29th Annual Rutgers Turfgrass Symposium. Volume 29, page 28.
• Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Chen, Q., B. Aleem, J.F. White and M.T. Elmore. 2020. Microbiome analysis of annual bluegrass seeds. Proceedings of the 29th Annual Rutgers Turfgrass Symposium. Volume 29, page 37.
• Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Diehl. K.H., M.T. Elmore, J.A. Murphy, A.M. Koppenh�fer, O.S. Kostromytska. 2020. Annual bluegrass weevil (Listronotus maculicollis), overseeding, and paclobutrazol for annual bluegrass (Poa annua) in golf fairways. Northeastern Plant Pest and Soils Conference. Volume 73, page 61.
• Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Tuck, D.P. and M.T. Elmore. 2020. Smooth crabgrass control programs with chelated iron weed control products. Northeastern Plant Pest and Soils Conference. Volume 73, page 109.

Progress 10/01/18 to 09/30/19

Outputs
Target Audience:Other scientists and professional practitioners. Changes/Problems:It has been tough to gain approval and find resources to advance Objective 2 beyond the results reported in the journal article. What opportunities for training and professional development has the project provided?Graduate student Katherine Diehl was responsible for various projects to understand whether annual bluegrass weevil can be used as a biological tool for annual bluegrass control as part of her MS thesis. She will defend her thesis in January 2020. Her responsibilities were to implement various treatments and measure responses. She was also responsible for monitoring annual bluegrass weevil populations at the various field research sites. Undergraduate students Andrew Petryna and Liam Ryan also assisted with projects associated with objectives 1 to 3. Katherine Diehl also assisted with laboratory experiments exploring bacteria associated with smooth crabgrass seed. As part of this project she learned sterile laboratory techniques, media preparation, DNA extraction, purification and sequencing, among other skills. How have the results been disseminated to communities of interest?The results of the annual bluegrass weevil research and the core-cultvation research were presented to professional turfgrass managers at the Rutgers Turfgrass Research Field Days where over 800 persons were in attendance. They were presented at various Extension presentations given by the PI in lecture at various meetings across the United States. It is estimated that results of this research were communicated to at least 900 professional turfgrass managers during the reporting period. What do you plan to do during the next reporting period to accomplish the goals?Research to explore the Pantoeabacteria strain isolated from smooth crabgrass in a controlled (greenhouse) environment to determine their impact on competitor species should be conducted. Field research to explore integrated strategies for smooth crabgrass control with alternative/organic herbicides needs to be conducted.

Impacts
What was accomplished under these goals? Objective 1: The results of research conducted in several locations in 2017, 2018, and 2019 indicate that the annual bluegrass weevil can be used as part of an integrated weed management program for annual bluegrass control in creeping bentgrass fairways. We found that modifying the industry standard insecticide programs to allow the annual bluegrass weevil to feed on annual bluegrass resulted in annual bluegrass control. This control was improved when this modified inseciticde program was combined with herbicide products that can also provide partial annual bluegrass control. Objective 2: We isolated over 20 strains of bacteria from the seeds of annual bluegrass and smooth crabgrass. Of these strains, several of those from smooth crabgrass but not annual bluegrass were pathogenic to competitor plant species common dandelion and white clover. The most pathogenic isolates were studied in more detail and determined to be Pantoea ananastis.This research suggests that smooth crabgrass seed harbors microbes that can make competitor plant species grow more slowly. However, this research was conducted in sterile culture and should continue in a greenhouse environment to explore this hypothesis in further detail. Objective 3: The results of two research trials in 2017, 2018, and 2019 indiciate that the time of year in which core cultivation is performed does not affect crabgrass encroachment. This research was conducted in both tall fescue and Kentucky bluegrass, two common lawn grasses in the northern US. The results of this research suggest that turfgrass managers can core cultivate in the springtime to improve soil structure for turf growthand not be concerned about making crabgrass worse. Objective 4: The annual bluegrass weevil work described in Objective 1determined that the annual bluegrass weevil can be used in conjunction with the herbicide paclobutrazolas part of an integrated weed management program. Adding creeping bentgrass interseeding to this program did not improve annual bluegrass control.We plan to take the results of Objective 3 (which were not conclusive until 2019) and develop research to explore integrated weed management programs in 2020.

Publications

• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: Diehl. K, M. Elmore, A. Koppenhofer, J. Murphy, D. Tuck and O. Kostromytska. 2019. Annual bluegrass weevil (Listronotus macuilicollis) and paclobutrazol for annual bluegrass (Poa annua) control in fairways. Northeastern Plant Pest and Soils Conference. Volume 72, page 5.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Elmore, M.T., J.F. White, K.L. Kingsley, K.H. Diehl, and S.K. Verma. 2019. Pantoea spp. associated with smooth crabgrass (Digitaria ischaemum) seed inhibit competitor species. Microorganisms. 7:143; 14 pp. doi:10.3390/microorganisms7050143
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: Diehl. K.H., M.T. Elmore, J.A. Murphy, A.M. Koppenhofer, O.S. Kostromytska. 2019. Annual bluegrass weevil (Listronotus maculicollis) and paclobutrazol for annual bluegrass (Poa annua) in creeping bentgrass (Agrostis stolonifera) fairways. 2019 Crop Science Society Meeting Abstracts. Paper 39-7. 1 page.

Progress 10/01/17 to 09/30/18

Outputs
Target Audience:Other scientists and green industry professionals Changes/Problems:In 2018 we foundthat chelated iron (Fe-HETDA) is an alternative to synthetic herbicides that we evaluated for both broadleaf weed control and crabgrass. We did not initially discuss an evaluation of chelated iron for weed control in the proposal because did not expect it to be very effective.However, our 2017 and 2018 results demonstrate that two sequential applications of Fiesta brand chelated iron made 30 days apart can provide good white clover control in cool-season turfgrass lawns. Chelated iron is more effective and more selective for broadleaf weeds than other alternative/organic weed control options evaluated. We also found that two applications of Fiesta chelated iron can provide some smooth crabgrass control. This is a novel finding and we will repeat the experimentin 2019. Fiesta herbicide has promise as an important component of a low impact integrated management strategy for weed controlit isincluded the progress report. What opportunities for training and professional development has the project provided?Graduate student Katherine Diehl was responsible for various projects to understand whether annual bluegrass weevil can be used as a biological tool for annual bluegrass control as part of her MS thesis. Her responsibilities were to implement various treatments and measure responses. She was also responsible for monitoring annual bluegrass weevil populations at the various field research sites. Undergraduate students Alex Coward, Chris Cote, and Benny Tran assisted withthe annual bluegrass weevil project, the crabgrass cultivation project, and the chelated iron for weed control projects. Program technician Daniel Tuck helped developed the idea and protocols associated with the chelated iron for weed control project. Katherine Diehl also assisted with laboratory experiments exploring bacteria associated with smooth crabgrass seed. As part of this project she learned sterile laboratory techniques, media preparation, DNA extraction, purification and sequencing, among other skills. Katherine also gave one scientific presentation on the smooth crabgrass endophyte project. How have the results been disseminated to communities of interest?The results of the annual bluegrass weevil research and the core-cultivation research were presented to professional turfgrass managers at the Rutgers Turfgrass Research Field Days where over 400 persons were in attendance.A popular press article was published in a magazine for golf course superintendents in January 2018. Information on chelated iron for weed control was presented to over 100 turfgrass managers at the New Jersey Turfgrass Association Expo Education Conference in December 2017. What do you plan to do during the next reporting period to accomplish the goals?Twoscientific abstracts were submitted for meetings in the 2019 reporting periodto discuss the results of the annual bluegrass weevil research. This research will be prepared for publication in a scientific journal in 2019. The results of the core-cultivation for crabgrass control project were presented to over 200 turfgrass managers at the Missouri Green Expo in December 2018 and the New England Sports Turf Managers Association Education Day in November 2018. Information on chelated iron for weed control will be included in several presentations to green industry professionals scheduled forwinter 2018-2019.

Impacts
What was accomplished under these goals? Preliminary findings of this project were: 1) The annual bluegrass weevil demonstrates selectivity as a biological control of annual bluegrass, but the weevil is not very effective when used alone. Annual bluegrass control with the annual bluegrass weevil alone was transient. For example, when annual bluegrass weevil was not present, annual bluegrass cover in July was ~40%. When the annual bluegrass weevil was present, annual bluegrass cover was ~30% in July. But there was no difference between these treatments a month later in August. When plant growth regulators (that suppress annual bluegrass) were combined with the weevil, annual bluegrass cover was ~10% in July and ~20% in August. Our 2017 and 2018 data suggest annual bluegrass weevil combined with plant growth regulatorshavepotential as a practical biological control, but more research is needed before this strategy can be adopted widely by practitioners. 2) Bacteria isolated from smooth crabgrass seeds can kill broadleaf weed seedlings in petri dishes in a laboratory. These isolates generally do not affect the grasses we have tested, but kill broadleaf weed seedlings such as white clover, common dandelion, and curly dock when bacterial suspensions are inoculated onto seeds. Two particular isolates (sequenced and determined to bePantoea ananatis)caused >80% mortality to white clover and dandelion seedlings, but less than 35% mortality to smooth crabgrass in petri dish experiment. Meanwhile another Pantoea speciesstrain included in the experiments as a negative standard caused 0% mortality of white clover seedlings. These isolates were included in a patent with other microbes from a collaborator laboratory. 3) Just as in 2017,core cultivation did not increase crabgrass incidence in a simulated lawn, regardless of when the core-cultivation treatments were performed in 2018. There was a slight trend that core-cultivation in May (when most crabgrass seedlings germinate) increased crabgrass incidence as plots core cultivated in May had 15% crabgrass cover in August compared to 10% for plots core-cultivate in the autumn, but this differencewas not statistically significant. This non-significant trendgives us impetus to continue this experimentfor one more season. These findings suggest that core-cultivation should be used to encourage the growth of healthy turfgrass during both the spring and the fall, even if pre-emergence herbicides are not applied to control crabgrass. 4) In 2018 we foundthat chelated iron (Fe-HEDTA) is an alternative to synthetic herbicides that we evaluated for both broadleaf weed control and crabgrass. We did not initially discuss evaluating chelated iron for weed control in the proposal because did not expect it to provide good weed control. However, our 2018 results demonstrate that two sequential applications of Fiesta (a brand of Fe-HEDTA chelated iron) made 30 days apart can provide good white clover control in cool-season turfgrass lawns. Chelated iron is more effective and more selective for broadleaf weeds than other alternative/organic weed control options evaluated. We also found that two applications of Fiesta chelated iron can provide some smooth crabgrass control. Two application of Fiesta provided 87% smooth crabgrass control in August compared to 0% control provided by corn gluten meal, a common organic pre-emergent crabgrass control product. This is a novel finding and we will repeat the experimentin 2019. Fiesta herbicide has promise as an important component of a low impact integrated management strategy for weed controlit is included the progress report.

Publications

• Type: Conference Papers and Presentations Status: Other Year Published: 2018 Citation: Elmore, M.T., J.F. White, K.L. Kingsley, K.H.D. Diehl, and D.P. Tuck. 2018. Bacteria of smooth crabgrass (Digitaria ischaemum) seed inhibit competitor species. Northeastern Plant Pest and Soils Conference. Volume 72, page 16.
• Type: Conference Papers and Presentations Status: Other Year Published: 2018 Citation: Elmore M.T., J.F. White, K.L. Kingsley, K.H.D. Diehl, D.P. Tuck, and S.K. Verma. 2018. Bacteria of smooth crabgrass (Digitaria ischaemum) seed increase broadleaf weed seedling mortality. Proceedings of the Weed Science Society of America Annual Meeting. Volume 58, page 104.

Progress 08/18/17 to 09/30/17

Outputs
Target Audience:Other scientists and professional practitioners. Changes/Problems:Our research investigating cultural practices and crabgrass infestation in turfgrass was designed to be collaborative with colleagues at other universities to provide a more robust set of data. Other colleagues were not successful in cultivating smooth crabgrass infestation for this research and one other colleague moved on to another position. Rutgers University is likely going to be the only collaborator with sufficient data to contribute to this effort. What opportunities for training and professional development has the project provided?Graduate student Katherine Diehl was responsible for various projects to understand whether annual bluegrass weevil can be used as a biological tool for annual bluegrass control as part of her MS thesis. Her responsibilities were to implement various treatments and measure responses. She was also responsible for monitoring annual bluegrass weevil populations at the various field research sites. She was assisted by undergraduate students Alex Coward and Sekou Sako. Katherine Diehl also assisted with laboratory experiments exploring bacteria associated with smooth crabgrass seed. As part of this project she learned sterile laboratory techniques, media preparation, DNA extraction, purification and sequencing, among other skills. How have the results been disseminated to communities of interest?The results of the annual bluegrass weevil research and the core-cultvation research were presented to professional turfgrass managers at the Rutgers Turfgrass Research Field Days where over 400 persons were in attendance. What do you plan to do during the next reporting period to accomplish the goals?We plan to repeat experiments initiated in 2017. We are currently planning research trials for 2018 to explore concepts supported by 2017 research in more detail.

Impacts
What was accomplished under these goals? The preliminary findings of this project were: 1) The annual bluegrass weevil has potential as a biological control of annual bluegrass on golf course fairways. Results were not consistent across locations,therefore,2018 research will be important to determine the efficacy of annual bluegrass weevil as a biological control of annual bluegrass. 2) That smooth crabgrass seed may vector bacteria the increase its competitiveness against other weeds. 3) That core-cultivation did not increase incidence of smooth crabgrass in a simulated lawn, regardless of when the core-cultivation was performed. These results suggest that core-cultvation can be utilized as a cultural practice to increase turf density and prevent weed infestations in organic systems or those that apply limited synthetic herbicides.Research will be repeated in 2018 to confirm 2017 results. Research in 2018 will confirm 2017 results and explore these findings in more detail. Subsequent years will use findings of this project to develop integrated weed management approaches.

Publications

• Type: Other Status: Awaiting Publication Year Published: 2017 Citation: Elmore, M.T., Diehl K.H., Koppenhofer, A.M., and Murphy, J.A. 2017 Controlling Poa annua in creeping bentgrass fairways. Golf Course Management Magazine (in press)