Download - What to Do About Weeds
What to Do About Weeds
Developed by: Susan DonaldsonUniversity of Nevada Cooperative Extension UNCE, Reno, Nev.
Topics to be covered What is a weed? Why worry about weeds? How weeds are regulated? Weed biology Factors that lead to plant invasion Preventing invasion and spread of weeds Identifying weeds Control - mechanical, cultural, biological, and
chemical Common weeds in your area
USDA-ARS
What’s a weed?
Invasive weed spreadWeed Annual Spread Reduced Grazing
Dyers woad 14% 38%
Canada thistle 10% 42%
Dalmation toadflax 8% 46%
Tall whitetop 9% 55%
Leafy spurge 12% 59%
Yellow starthistle 17% 65%
Spotted knapweed 24% 80% UNCE, Reno, Nev.
Weed impacts Decreased grazing
potential Economic losses
from refusals of hay shipments
Decreased crop yields
Cost of controlUNCE, Reno, Nev.
Weed impactsDecreased property values
Loss of wildlife and fish habitat
Impairment of wetland functions
Increased erosionToxicityUNCE, Reno, Nev.
Damaging to the economy or environment Difficult to control Dominate sites
Thre
e D
’s
Dicot (Broadleaf)
•Two true leaves• Broad leaves
have net-like veins
•Coarse tap root
Monocot(Grass)
•One seed leaf•Parallel veins •Fibrous roots
How weeds grow
Monocot Vs Dicot
Plant life cycles Annual
◦ One season for all stages of development
◦ Produce foliage, flower seeds, then die
Yellow starthistleUNCE, Reno, Nev.
Summer annuals◦ Live from spring to fall◦ Examples:
◦ foxtail, pigweed Winter annuals
◦ Germinate in fall and winter
◦ Examples:◦ cheatgrass and
mustard
Plant life cycles Biennials
◦ Require two seasons for completion of life cycle
◦ First year: develop roots and low-growing leaves
◦ Second year: flowers, sets seed and matures
◦ Examples are mullein and musk thistle
UNCE, Reno, Nev.
Musk thistle
Plant life cycles
Perennials◦ Live more than two years◦ Will produce foliage, seed,
and reach maturity each year
◦ Examples: perennial pepperweed Canada thistle
UNCE, Reno, Nev.
Dandelion
Reproduction Annuals and biennials
◦ Seed ◦ Seed bank
Perennials◦ Simple: Reproduce by seed and pieces of root
◦dandelions◦ Bulbous: Produce seed, bulblets and bulbs
◦wild onion◦ Creeping: Produce seeds, rhizomes (underground
stems), stolons (above ground stems), or creeping roots
◦pepperweed
UNCE, Reno, Nev.
Plant parts for broadleaf identification
NRCS, Bozeman, Mont.
Identifying weeds
Have you correctly identified the weed?
Tumble mustard
Spotted knapweed
Dandelion
Yellow starthistle
How do weeds ensure their success?
They are very competitive◦ Grow well in spite of interference from other
plants They take advantage of the characteristics
of sites, including:◦ Exposed or disturbed soil (grading road
shoulders)
◦ Turfgrass, range, pasture or groundcover that is weakened by disease, pests, or poor management
◦ Places where a desired species is not well-adapted to its environment
UNCE, Reno, Nev.
How do weeds ensure their success?
They are persistent◦ Will return year
after year
◦ Reproduce vigorously
◦ Spread seeds effectively
UNCE, Reno, Nev.
How do weeds ensure their success?
They are harmful◦ Can alter the site
they grow in by◦ accumulating salts, ◦ changing water
table depths, ◦ increasing erosion, ◦ increasing wildfire
frequency, ◦ Etc.
UNCE, Reno, Nev.
How do weeds spread? Natural means
◦ Wind◦ Water ◦ Animals
Humans◦ Irrigation◦ Roadside shoulder work◦ Construction/ fill dirt◦ Vehicles◦ Tillage◦ Contaminated seed or feed◦ Livestock management
UNCE, Reno, Nev.
What can we do? Practice Integrated Pest Management (IPM)
IPM is a sustainable approach to managing pests that combines biological, cultural, physical and
chemical tools in a way that minimizes economic, health, and
environmental risks
UC Davis
Hand removal of weeds
Sticky traps and other physical traps/barriers
Components of an IPM program Planning Setting action thresholds Monitoring and detection Identification Implementation Evaluation
IPM tools for weed management (IWM) Prevention
Eradication Mechanical controls Cultural controls Biological controls Chemical controls
Building a weed management planCONSIDER THE:
Identity of the weed Biology of the weed Extent of the problem Environmental conditions of the site Ultimate objectives for the site Most economical solution
UNCE, Reno, Nev.
Method 1 of IWM:Prevent the invasion and spread of weeds
Plant clean, weed-free seed Avoid spreading weed seeds with manure Sanitize tillage and harvest equipment prior
to moving them from one field to another Plant and maintain desirable plant species Consider crop rotation to slow weed spread
Minimize soil disturbance and bare ground
Don’t overgraze pastures Apply the appropriate
amount of water Avoid driving in weed-
infested areas
Method 1 of IWM:Prevent the invasion and spread of weeds
USDA NRCS
Method 1 of IWM:Prevent the invasion and spread of weeds
Don’t transport flowering plants that you cannot identify
Pull small patches before seed is formed
Carefully remove weeds that have flowered
Report new infestations
Method 2 of IWM:Eradication
Removal of all weeds of a given species from an area so they will not recur unless reintroduced
Must deplete seed bank of viable weed seeds by controlling all seedlings
Only feasible for small, new invasions Must revegetate the area
Method 3 of IWM: Mechanical Control Cultivation Hoeing Bulldozing Burning Hand pulling Mowing
UNCE, Reno, Nev.
CSUCE
Mulching Solarizing (use clear
plastic for maximum affect)
Repeated tillage can help reduce seed populations UNCE, Reno, Nev.
Method 4 of IWM:Cultural control
Cultural control involves using land management tools that make it difficult for weeds to be successful◦ Shading◦ Water and nutrient management◦ Correct seeding rates
Method 5 of IWM:Biological control
Biological control is the use of one organism to suppress another◦ Can reduce pesticide use◦ Agents can be free or
purchased◦ Can effectively and
economically suppress pests
◦ Does not eradicate a weedUNCE, Reno, Nev.
Method 5 of IWM:Biological control
Characteristics of successful biocontrol agents:◦ Prolific◦ Thrive and become
widespread in all habitats and climates that the pest weed occupies.
◦ Good colonizers of new areas.
Leaf eating beetle (Diorhabda elongata)
on tamarisk
NDOA
Tamarisk biocontrol
NDOAhttp://www.tamariskcoalition.org/
Method 6 of IWM:Chemical control
UNCE, Reno, Nev.
CSUCE
Manage pastures to minimize weeds
USDA NRCS
Herbicides
Prevention
Proper fertility and species
Dense vegetation, no bare spots
Managed grazing
Naming herbicides Chemical name
◦ N-(phosphonomethyl)glycine Common name
◦ Glyphosate Trade or brand name
◦ RoundUp, Aquamaster, Glypro, Rodeo, etc.
Brand◦ Monsanto
www.scotts.com
Pesticides: an all-inclusive term for all “cides”
Herbicide Fungicide Insecticide
Rodenticide …
To spray or not to spray?Consider: The goals for the site The site conditions
◦ Accessibility◦ Proximity to surface water◦ Depth to groundwater◦ Presence of rare species
Effectiveness against target species
Behavior in the environment
Toxicity Safety
Twelve steps to follow before using herbicides:
1. Identify the weeds2. Determine their life cycles3. Consider all control alternatives4. Select the chemical based on
effectiveness, safety, and price5. Read the label carefully and make
sure the herbicide is labeled for the pest and the site
6. Determine the best time to apply the chemical
7. Is the chemical restricted-use-only?8. Consider proximity to water, nearby trees
or shrubs, soil composition, tendency to contaminate water supplies
9. Check the weather 10. Have you read the MSDS?11. Are you applying the appropriate amount
by the best method?12. Do you understand all safety
requirements, and have you followed them carefully? (PPE)
Twelve steps to follow before using herbicides:
Pesticide toxicity
CautionWarningDanger
Less toxic
More toxic
How do herbicides work? Interfere with or disrupt biochemical or
physiological processes in susceptible plants
Often affect a specific enzyme or reaction Example: amino acid inhibitors - glyphosate
Chemical control Selective
◦ Kills only a specific plant or type of plant
◦ Most common types are broadleaf vs. grass USDA NRCS
ALWAYS READ AND FOLLOW THE LABEL DIRECTIONS!
Examples of selective herbicides 2,4-D (Weed-b-Gone, Weedar 64) picloram (Tordon, retricted use, persistent) chlorsulfuron (Telar, Glean) triclopyr (Garlon 3A)
Nonselective herbicides Kills most or all of the vegetation in the
area covered May be pre-mergent or postemergent
chemicals
ALWAYS READ AND FOLLOW THE LABEL DIRECTIONS!
Examples of nonselective herbicides ◦ glyphosate (Roundup)◦ imazapyr (Arsenal; use pre-emergence or
postemergence; has a long residual in high pH soil)
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 to minimize spray drift
UNCE, Reno, Nev.
Now what? Go home and inventory and identify the
weeds on your property Why do you have a weed problem?
What can you change about the way you manage your property to decrease weeds?
Determine the most appropriate controls for the site
Make weed management plan Start working! Monitor your property for weeds on a
continual basis
Successful weed management requires constant vigilance and care on the part of the
land manager.
CSUE