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Responding to Lawn Weed Management Questions Dr. John Stier University of Wisconsin-Madison Environmental Turfgrass Extension Specialist.

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Presentation on theme: "Responding to Lawn Weed Management Questions Dr. John Stier University of Wisconsin-Madison Environmental Turfgrass Extension Specialist."— Presentation transcript:

1 Responding to Lawn Weed Management Questions Dr. John Stier University of Wisconsin-Madison Environmental Turfgrass Extension Specialist

2 Presence of Weeds Usually Indicates Underlying Problem Turfgrasses adapted to the local environment resist weeds best

3 Good Turf Management Mowing –2-3 inch height: 1/3 Rule –Sharp blades Fertility –3-4 lb N/1000 ft 2 : Holiday Schedule Irrigation Turf species –Kentucky bluegrass/perennial ryegrass –Fine fescue: low maintenance, dry shade –Rough or supina bluegrasses for moist shade

4 Moss and Algae Low light Restricted air movement Poor drainage Often compounded by poor management

5 Why do I Have Weeds in My Lawn Again This Year? Correct product used? –Age, storage Rate? Timing? –Rain, growing conditions –Temperature Low-restrict absorption/translocation Warm to mod. high-best absorption/translocation V. high-dries on surface prior to absorption Turf cover & management

6 Post-Emergent Grassy Weed Control Difficult Annuals: crabgrass –MSMA: retail Perennials: tall fescue, bentgrass, quackgrass, nimblewill –Glyphosate (Roundup, Kleenup)

7 Creeping Bentgrass Poor quality seed –May take years to become noticeable –Puffy patch, small- leaved grass Fine stolons easily ripped up Spray glyphosate 1 ft past perimeter of patch Bentgrass patch 1 ft stolons

8 Pre-Emergent Weed Herbicides Form barrier between soil surface and seed –Irrigation or rainfall Prevent seed germination –apply March-April –Used for annual grasses, some broadleaves –Will stop perennial germination Examples:pendimethalin dithiopyr (some post-emergent) siduron--OK for seeding

9 Crabgrass and Quackgrass Spring and summer Light green color Brown after frost Short, wide leaves Fine hairs on leaves/stem Easy to pull plant Perennial Gray-green color Longer, narrower leaves Few hairs Auricles Cant pull plant Rhizomes

10 Post-Emergent Broadleaf Herbicides Apply to visible weeds when actively growing Broadleaf weed control: 2,4-D; MCPP; MCPA; dicamba; triclopyr –Sold in combinations (e.g., Weed-B-Gon) –Dicamba is soil mobile, can damage taxus, junipers, others

11 Factors Affecting Herbicide Control Formulations –Esters volatile readily absorbed use during cool temps or hard-to-kill weeds –Salts less volatile use during hot temps less smell Wild violet

12 Weed and Feed Products Herbicide impregnated on fertilizer prill Post or pre-emergence Post: Stick to leaves? Pre: Timing?

13 Non-Toxic Pesticides Misnomer: Pesticides intended to be toxic to pests EPA regulates toxicity: no significant danger when used properly Avoid reliance on non-regulated biological or organic pesticides –May not work –No toxicity testing!

14 LD 50 and LC 50 Measure & Rate Acute Toxicity Amount to kill 50% of animals = Lethal Dose to 50% (LD 50 ) LC 50 = Inhalation Toxicity Lower LD or LC 50 values = More toxic!

15 Toxicity of Common Substances CuSO4Bordeaux Mixture Fungicide11 Caffeine--- 192 2,4-DVariousHerbicide375-666 *Aspirin--- 1240 *Table salt--- 3320 GlyphosateRoundupHerbicide5800 LD 50 Source: Pesticide profiles: Toxicity, environmental impact, & fate. 1997. M.A. Karmin (ed). Lewis Publishers *Source: Applied weed science. 1999. M.A. Ross & C.A. Lembi. Prentice-Hall. 3500 ppm = 10 oz ai/180 lb adult

16 EPA: 2,4-D Not Linked to Human Cancer (9 Aug. 2007) 300 studies since 1989 "Based on extensive scientific review of many epidemiology and animal studies, the Agency finds that the weight of the evidence does not support a conclusion that 2,4- D, 2,4-DB and 2,4-DP are likely human carcinogens," according to a notice released by EPA.

17 Pesticide Fate Pesticide Applied (Volatilize) (Drift) Photodecomposition Runoff ? Plant Uptake & Degradation Thatch Adsorption Microbial decomposition Soil Chemistry Reactions and Decomposition Leaching?

18 Corn Gluten Meal Accidental discovery Research-based! Activity –Herbicidal(?) –Fertility (10% N)

19 Corn Gluten Meal Application 12-20 lb/M –Early spring –Late summer Irrigate Timing critical –Short-lived peptides

20 Crabgrass Reduction in Field Trials of Corn Gluten Meal on Kentucky Bluegrass Adapted from Christians, N.E. 1993. The use of corn gluten meal as a natural preemergent weed control in turf. ITS No. 7. Intertec Publishing Corp., Overland Park, KS, p. 284-290.

21 Corn Gluten Meal for Weed Control High use rates (12-20 lb/M) –One to two applications annually Expensive: $25-$45 per application/M Pre-emergent only Overseeding limitations Fertility effect

22 Other Ways to Reduce Risk Use pesticides only when necessary –Integrated Pest Management Choose products with lower toxicities Follow ALL label instructions –Gloves, rates, disposal Remember… –Risk = Toxicity x Exposure!

23 Conclusion A little herbicide goes a long way if… Turf is properly managed!


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