Title: Responding to Lawn Weed Management Questions
1Responding to Lawn Weed Management Questions
- Dr. John Stier
- University of Wisconsin-Madison
- Environmental Turfgrass Extension Specialist
2Presence of Weeds Usually Indicates Underlying
Problem
- Turfgrasses adapted to the local environment
resist weeds best
3Good Turf Management
- Mowing
- 2-3 inch height 1/3 Rule
- Sharp blades
- Fertility
- 3-4 lb N/1000 ft2 Holiday Schedule
- Irrigation
- Turf species
- Kentucky bluegrass/perennial ryegrass
- Fine fescue low maintenance, dry shade
- Rough or supina bluegrasses for moist shade
4Moss and Algae
- Low light
- Restricted air movement
- Poor drainage
- Often compounded by poor management
5Why 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
6Post-Emergent Grassy Weed Control
- Difficult
- Annuals crabgrass
- MSMA retail
- Perennials tall fescue, bentgrass, quackgrass,
nimblewill - Glyphosate (Roundup, Kleenup)
7Creeping 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
8Pre-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
9Crabgrass 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
10Post-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
11Factors Affecting Herbicide Control
Wild violet
- Formulations
- Esters
- volatile
- readily absorbed
- use during cool temps or hard-to-kill weeds
- Salts
- less volatile
- use during hot temps
- less smell
12Weed and Feed Products
- Herbicide impregnated on fertilizer prill
- Post or pre-emergence
- Post Stick to leaves?
- Pre Timing?
13Non-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!
14LD50 and LC50 Measure Rate Acute Toxicity
- Amount to kill 50 of animals Lethal Dose to
50 (LD50) - LC50 Inhalation Toxicity
- Lower LD or LC50 values More toxic!
15Toxicity of Common Substances
LD50
3500 ppm 10 oz ai/180 lb adult
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.
16EPA 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.
17Pesticide Fate
Photodecomposition
(Volatilize)
Pesticide Applied
(Drift)
Runoff ?
Plant Uptake Degradation
Thatch Adsorption
Microbial decomposition
Soil Chemistry Reactions and Decomposition
Leaching?
18Corn Gluten Meal
- Accidental discovery
- Research-based!
- Activity
- Herbicidal(?)
- Fertility (10 N)
19Corn Gluten Meal Application
- 12-20 lb/M
- Early spring
- Late summer
- Irrigate
- Timing critical
- Short-lived peptides
20Crabgrass 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.
21Corn 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
22Other 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!
23Conclusion
- A little herbicide goes a long way if
- Turf is properly managed!