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Spring and Fall Preemergence Weed Control Options for Turf

Dr. Tim R. Murphy
Extension Weed Scientist
University of Georgia
Griffin, GA

• Slide Presentation (PowerPoint, 53 KB)

TABLE OF CONTENTS

Spring and Fall Preemergence Weed Control Options for Turf Preemergence Options Repeat Applications - Summer Goosegrass Crabgrass spp. Annual bluegrass Continuous Annual Bluegrass Germination Preemergence Herbicides Guidelines - Preemergence Fertilizer/Preemergence Products Fertilizer/Preemergence Products - Other Considerations Preemergence Herbicides - Formulation Effects Preemergence Herbicides - Formulation Effects Preemergence Herbicides - Formulation Effects Weed Life Cycles Weeds can be a problem all 12 months What is the best Herbicide? It Depends... Preemergence Herbicide Selection Preemergence Herbicide Selection Suggested Application Dates Lack of Preemergence Herbicide Performance

SLIDE CONTENTS

Spring and Fall Preemergence Weed Control Options for Turf Dr. Tim R. Murphy Extension Weed Specialist University of Georgia Griffin Preemergence Options Repeat Applications - Summer Space 8 to 10 wks apart Apply 1/2 X fb 1/2X May improve control of crabgrass and goosegrass 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 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 Annual bluegrass Winter annual Germinates late summer-fall at soil temperatures around 70 F. Second germination flush in mid- to late-winter PPT Slide Continuous annual bluegrass seed germination occurred from mid-Nov. through early January in Knoxville, TN. Callahan and McDonald, 1992 Preemergence Herbicides Need rainfall or irrigation (1/2 inch) Do not control emerged weeds Granular or sprayable Most available on dry fertilizer carriers Guidelines - Preemergence Labeled products only Established turfgrass Apply before weed emergence Need rainfall or irrigation within 5 days Consider split applications Delay mowing until after incorporation Know future plans 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 Yelverton, et al., 1996 Preemergence Herbicides- Formulation Effects Johnson and Murphy, 1991 Preemergence Herbicides- Formulation Effects Johnson and Murphy, 1991 Weed Life Cycles Summer annuals - < 1 yr. Winter annuals - ə yr. Biennials - 2 yr. Perennials - > 2 yr. PPT Slide Weeds can be a problem in all 12 months. PPT Slide What is the best preemergence herbicide for turfgrasses?? PPT Slide 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?? Suggested Application Dates North Georgia Spring, March 1 - 20 Fall, August 20 - Sept. 15 South Georgia Spring, Feb. 10 - March 1 Fall, Sept. 20 - Oct. 15 Early is always better than late! Lack of Preemergence Herbicide Performance No rainfall or irrigation Excessive rainfall shortly after application High rainfall year Poor site drainage Drought Rate too low Mow/Bag before incorporation