Turfgrass Weed Management I Methods II Grass Weed Control Tim R Murphy Crop and Soil Sciences The University of Georgia The Goal Establish and maintain a high quality nearly weed free turfgrass Turfgrass Weeds Reduce quality Reduce density Decrease aesthetic value or utility of the turfgrass Develop A Plan Goals Economics Alternatives Benefits Weed Management Strategy Diagnose problem Evaluate control methods Select program Execute program Evaluate Identify the Weed Problem READ textbooks and periodicals Keep a diagnostic tool kit hand lens etc Know the life cycle of the pest What temp does a specific weed seed germinate Is the weed the cause or effect of the problem Confirm your diagnosis Weed Life Cycles Summer annuals 1 yr Winter annuals 1 yr Biennials 2 yr Perennials 2 yr Weeds can be a problem in all 12 months Integrated Weed Management Preventive Cultural Biological Mechanical Herbicides Preventive Methods State and federal laws Weed free seed plant material Topsoil no nutsedge Clean equipment Field borders Cultural Methods Adapted turfgrasses Fertility management Cultivation practices Irrigation Pest control Soil Fertility Effects on Weeds Low N legumes mosses High P annual bluegrass High N common chickweed Low soil pH red sorrel broomsedge Weeds Favored in Compacted Soils Annual bluegrass Goosegrass Prostrate knotweed Common lespedeza Path rush Weeds Favored by High Soil Moisture Sedges purple nutsedge green kyllinga Rushes Annual bluegrass Mosses Weeds Favored by Low Soil Moisture Prostrate spurge Poorjoe Common lespedeza Prostrate knotweed Maintain Healthy Turfgrass Manage the roots to have good shoots Soil testing is a must Utilize cultural practices fertility irrigation mowing height etc to improve stress tolerance Keep mower blades sharp Use the best species and cultivars for your location Preemergence herbicides are the foundation of annual grass control Herbicide layer Weed seeds germinate and are controlled as they come in contact with the herbicide Turfgrass roots below the herbicide layer Preemergence herbicides do not prevent weed seeds from germinating Preemergence Options Atrazine Simazine Balan XL TeamPro Surflan Barricade Pendimethalin Kerb Dimension Bensulide Pennant Gallery Ronstar The majority of herbicides used for preemergence annual grass control are dinitroanilines and dithiopyr DNA s Barricade Pendulum Surflan Balan Treflan Dimension Best used on established turf Mitotic inhibitors Relatively immobile in the soil What is the best preemergence herbicide for turfgrasses It depends Preemergence Herbicide Selection Turfgrass species Weed species Immature vs established Time of year Irrigation capabilities Renovation plans Preemergence Herbicide Selection Granular or spray equipment Desired control level Application frequency Ornamental tolerance Cost Annual Grass Control Ratings Herbicide Benefin Benefin oryzalin Benefin trifluralin Bensulide Dithiopyr Oryzalin Oxadiazon Pendimethalin Prodiamine Crabgrass G G E F G E G E G E G G E G E Goosegrass F F G F P F G F G G E F G F G Annual Bluegrass G E G E G E P F G E G E G E G E G E Crabgrass spp Summer annual At least 5 species in GA tropical smooth large southern blanket Germinates at soil temps 53 to 58 F 4 inch depth Light required Crabgrass spp Summer annual Southern crabgrass Smooth crabgrass Goosegrass Summer annual Germinates soil temp 4 inch depth averages 60 to 65 F Usually germinates 2 to 6 weeks later than crabgrass Light required goosegrass Summer annual Prefers compacted areas that are overwatered goosegrass crowfootgrass Goosegrass Cultural Controls Aerify to alleviate compaction Redirect traffic Control watering Encourage thick turf Core Aerification Previously thought to break up herbicide layer and reduce weed control Research shows little increased crabgrass or goosegrass due to core aerification Ronstar oxadiazon Not a mitotic inhibitor Preferred herbicide for sprigging or high traffic areas athletic fields tees etc Preferred herbicide for preemergence goosegrass control Will control crabgrass but is more effective on goosegrass Annual bluegrass Winter annual Germinates late summer fall at soil temperatures around 70 F Second germination flush in mid to late winter Continuous annual bluegrass seed germination occurred from mid Nov through early January in Knoxville TN Callahan and McDonald 1992 Annual bluegrass control Boat shaped leaf tip annual bluegrass Preemergence Control Barricade Pendulum Surflan Dimension Balan Ronstar Kerb Atrazine Simazine Preemergence Herbicides Need rainfall or irrigation 1 2 inch Do not control emerged weeds Preemergence Herbicides If irrigation is not available apply well in advance of expected weed germination to allow for an activating rainfall Loss of activity may occur if they are not watered in within 7 to 10 days Treflan Team is the most volatile Surflan the least volatile Losses from photodecomposition and volatilization Irrigation Timing and Formulation Effect on Crabgrass Control with Pendimethalin 45 Plants sq ft 40 35 30 25 WP Sprayable 7 watered in 7 days after application 20 15 10 5 0 GR 0 WP 0 GR 7 WP 7 GR granular 0 watered in immediately Relative Volatility of Preemergence Herbicides Volatility 2500 2000 2000 1500 1000 376 500 0 500 2 5 30 Surflan Ronstar 2 5 Pendimet Treflan Barricade Relative Solubility of Preemergence Herbicides Solubility ppm 250 200 200 150 77 100 50 23 17 Pendimet Treflan 0 Surflan Ronstar 0 013 Barricade Granular Formulations Poor Distribution of Active Ingredients Spreader not calibrated changes with age Bag settings are only guidelines Spreader and or product cause a skewing of product distribution over the turf Particle size too large for uniform coverage Lower application rates reduce uniform coverage Fertilizer Preemergence Products Correct fertilizer analysis Time of year N release characteristics Supplemental fertilizer applications Supplemental herbicide applications Fertilizer Preemergence Products Other Considerations Uniform coverage required Uniform particle size is important Release characteristics of fertilizer product Control equivalent to sprayable and granular products Preemergence Herbicides Formulation Effects Barricade 65WG lbs ai acre 0 75 Smooth Crabgrass Control 98 0 29G 0 75 91 0 5G 0 75 81 Yelverton et al 1996 Preemergence Herbicides Formulation Effects Control Dimension 1EC lbs ai acre 0 5 Smooth Crabgrass 64 Goosegrass 31 1EC 0 75 91 29 0 25G 0 25 82 55 0 25G 0 38 100 78 0 25G 0 5 100 82