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Montana Pesticide Education Montana Pesticide Education ProgramProgram
http://mtpesticides.orghttp://mtpesticides.org
Residential Weed Residential Weed ManagementManagement
Residential Weed Residential Weed ManagementManagement
What is considered a weed?
• Any plant growing where it is not wanted.
• Obnoxious Weeds– Toxic Weeds– Invasive and Noxious weeds are the most
troublesome.• Rapidly dominate the site• Very difficult to control
Weeds are Indicators of Site Conditions
• Salty Soils– Shepherds Purse, Russian Thistle
• Acid soils – Very Acid Soils– Horsetail – Hawkweed & Knapweed
• Badly drained soils– Horsetail
• Deep shade– Ground ivy, chickweed
Noxious Weeds in Montana• Landowners are responsible for controlling the spread noxious
weeds on their property
• Cat 1 = established & widespread
• Cat 2 = recently introduced and rapidly spreading
• Cat 3 = Not yet detected or in few locations
Category 1 Category 2
Noxious Weeds in MontanaCategory 3
Weed Management
• Buy clean seed for wildflowers or lawns; don’t plant weeds!
• Clean yard equipment before using it in another area
• Get weeds along streams under control
• Use mulch materials or weed mats
• Pull weeds early – before they go to seed!
Prevention is the most effective practice of all!
Control MethodsMechanical• Mowing, hand pulling, burning, solarizing
Cultural• Shading, site preparation, plant
appropriate competitive vegetation
Biological• Parasites, predators, and pathogens;
typically a slow process – not for urban
Chemical• Repeated application
• Plants must be growing
• USE ACCORDING TO LABEL
Weed Biology/Life Cycles
Exploit Weed Weaknesses
• Monocots: parallel leaf veins, growth points at/below soil levelGrasses
–Grass family
•Cheatgrass, quackgrass
–Sedge family
•Nutsedge
–Lily family
•Wild onion, death camas
Dicots: net-like leaf veins, diverse Dicots: net-like leaf veins, diverse growing pointsgrowing points
Many others
Broadleaf–Composite family
•Dandelions, thistles, knapweed
–Mustard family
•Shepherd's purse, lambsquarter, whitetop
–Carrot family
•Hemlock
Stages of Weed Development
• 1. Seedling
– Tender, vulnerable
• 2. Vegetative
– Great uptake of water and nutrients
• 3. Seed production
– Reduced uptake, energy directed to flowers, fruit
• 4. Maturity
– Little uptake or energy production
• Annual weeds: live one year – Summer annuals: seed & die by winter.
• Pigweed, lambsquarter, black medic
– Winter annuals: germinate in late summer, overwinter, produce seed, die the next season.
• Chickweed, curly dock, cheatgrass, black medic
Biennial weeds: broadleaf plants with a 2-year life cycle
Houndstongue, mullein, burdock, bull thistle
– mature, seed and die in second year
– vegetative growth first year (Rosette)
• Perennial weeds: live 3 or more years– most persistent
– difficult to control
– propagules• rhizomes, stolons, bulbs, tubers
– wide range of dicots and monocots
Managing Landscape Weeds
• Maintain competition – grazing management
• Prevent seed production
• Prevent seed germination
• Limit emerged weeds early
• Limit susceptible stages of mature weeds.
Chemical designed to control weeds. Plant, soil and weather conditions influence herbicidal activity.
Herbicide Characteristics
Contact Systemic
Herbicide Herbicide CharacteristicsCharacteristics
PersistentNon
Persistent
Herbicide Herbicide CharacteristicsCharacteristics
SelectiveNon
Selective
Herbicide Characteristics
• Application in relation to plant development
– Pre-plant• Before crop is planted
– Pre-emergent• Before weeds emerge
– Post emergent• After weeds emerge
Herbicides and Plant Characteristics
• Growing points
• Leaf shape and orientation
• Wax and cuticle
Herbicides and Plant Herbicides and Plant CharacteristicsCharacteristics
Leaf hairsLeaf hairs
DeactivationDeactivation
Life cycle stageLife cycle stage
Herbicide Effectiveness
0
20
40
60
80
100
seedling vegetative flowering mature
% control
Climatic Factors
• Relative humidity
• Light
• Precipitation
• Temperature
Biennial
2-5 feet tall
Flowers purple July-September
Reproduces by seed
Seed can be viable for 10 years
Bull Thistle (Cirsium vulgare)
Control:
hand pull
cut or mow before going to seed
herbicides? When?
Perennial
Flowers light pink-purple
Grows 1-4 feet tall
Has deep horizontal roots
Reproduces through creeping roots, some seed
Canada Thistle (Cirsium arvense)
Control:
pull by hand (small plants)
apply herbicides; spot-spraying young plants is very effective
Control:
hand pull or dig* (small plants)
apply herbicides in early spring or late fall*be sure to wear gloves & properly dispose of all plant material
Biennial
Grows to 10 feet tall
Tiny white flowers & purple-mottled stems
All parts of plant are highly poisonous (if eaten)
Reproduces by seed
Poison Hemlock (Conium maculatum)
Control: cut, dig, or hand pull (small plants) cut and remove the flowering spikes to prevent new seedlingsapply herbicides when actively growing at full to late flowering
Perennial
Flowers purple on spikes
Stems are square; plant can be 6-8 feet in height
Reproduces by seed and roots
Purple Loosestrife (Lythrum salicaria)
Weed treatment in riparian areas
• Select the most effective treatment methods for the site
• If herbicides are used, be sure the label allows application adjacent to or in the water
• Consider wipe application or hand removal
Sensitive areas
Where is this water going?
Non-target vegetation
Herbicides in a Residential Setting
Drift
Animals & kids
Concerns over chemical use
Movement of contaminated soil and vegetation
Hose End
Sprayers For Urban/Residential Use
Skid Mount
ATV & Lawn Tractor
BackpackHand Held
Spot Treatment < 1/10th acre
Up to 1 acre> 1 acre depending on tank size & GPA
General Precautions
Prevent Drift
Calibrate Your Sprayer Add the right amount
UseCommon
Sense
1.30% Dicamba 3.05% 2,4-D10.6% MCPP
8.0% Triclopyr
What To Use
Now what?• Inventory the plants on
your property
• Identify invasive plants and weeds
• Do you have a weed problem? Why?
• What can you change about the way you manage your property to decrease the weed population?
Then...• Determine appropriate
controls and your plans for the site and start working
• Monitor for invasive plants
• Plant native plants in your yard after the weeds are under control
• Share this information with others