Presentation on theme: "Responding to Lawn Weed Management Questions"— Presentation transcript:
1 Responding to Lawn Weed Management Questions Dr. John StierUniversity of Wisconsin-MadisonEnvironmental 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 Fertility Irrigation Turf species 2-3 inch height: 1/3 RuleSharp bladesFertility3-4 lb N/1000 ft2: Holiday ScheduleIrrigationTurf speciesKentucky bluegrass/perennial ryegrassFine fescue: low maintenance, dry shadeRough 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, storageRate?Timing?Rain, growing conditionsTemperatureLow-restrict absorption/translocationWarm to mod. high-best absorption/translocationV. high-dries on surface prior to absorptionTurf cover & management
7 Creeping Bentgrass Poor quality seed Fine stolons easily ripped up May take years to become noticeablePuffy patch, small-leaved grassFine stolons easily ripped upSpray glyphosate1 ft past perimeterof patchBentgrass patch1 ftstolons
8 Pre-Emergent Weed Herbicides Form barrier between soil surface and seedIrrigation or rainfallPrevent seed germinationapply March-AprilUsed for annual grasses, some broadleavesWill stop perennial germinationExamples: pendimethalindithiopyr (some post-emergent)siduron--OK for seeding
9 Crabgrass and Quackgrass Spring and summerLight green colorBrown after frostShort, wide leavesFine hairs on leaves/stemEasy to pull plantPerennialGray-green colorLonger, narrower leavesFew hairsAuriclesCan’t pull plantRhizomes
10 Post-Emergent Broadleaf Herbicides Apply to visible weeds when actively growingBroadleaf weed control: 2,4-D; MCPP; MCPA; dicamba; triclopyrSold in combinations (e.g., Weed-B-Gon)Dicamba is soil mobile, can damage taxus, junipers, others
11 Factors Affecting Herbicide Control Wild violetFormulationsEstersvolatilereadily absorbeduse during cool temps or hard-to-kill weedsSaltsless volatileuse during hot tempsless smell
12 Weed and Feed Products Herbicide impregnated on fertilizer prill Post or pre-emergencePost: Stick to leaves?Pre: Timing?
13 “Non-Toxic” Pesticides Misnomer: Pesticides intended to be toxic to pestsEPA regulates toxicity: no significant danger when used properlyAvoid reliance on non-regulated “biological” or “organic” pesticidesMay not workNo toxicity testing!“Non-Toxic” Pesticides
14 LD50 and LC50 Measure & Rate Acute Toxicity Amount to kill 50% of animals = Lethal Dose to 50% (LD50)LC50 = Inhalation ToxicityLower LD or LC50 values = More toxic!
15 Toxicity of Common Substances LD50CuSO4Bordeaux MixtureFungicide11Caffeine---1922,4-DVariousHerbicide*Aspirin1240*Table salt3320GlyphosateRoundup58003500 ppm = 10 oz ai/180 lb adultSource: Pesticide profiles: Toxicity, environmental impact, & fate M.A. Karmin (ed). Lewis Publishers*Source: Applied weed science M.A. Ross & C.A. Lembi. Prentice-Hall.
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.
20 Crabgrass Reduction in Field Trials of Corn Gluten Meal on Kentucky Bluegrass Adapted from Christians, N.E The use of corn gluten meal as a natural preemergent weed controlin turf. ITS No. 7. Intertec Publishing Corp., Overland Park, KS, p
21 Corn Gluten Meal for Weed Control High use rates (12-20 lb/M)One to two applications annuallyExpensive: $25-$45 per application/MPre-emergent onlyOverseeding limitationsFertility effect
22 Other Ways to Reduce Risk Use pesticides only when necessaryIntegrated Pest ManagementChoose products with lower toxicitiesFollow ALL label instructionsGloves, rates, disposalRemember…Risk = Toxicity x Exposure!
23 Conclusion A little herbicide goes a long way if… Turf is properly managed!