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What to Do About Weeds

What to Do About Weeds. Developed by: Susan Donaldson University 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

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What to Do About Weeds

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  1. What to Do About Weeds Developed by: Susan Donaldson University of Nevada Cooperative Extension UNCE, Reno, Nev.

  2. 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

  3. What’s a weed? USDA-ARS

  4. Invasive weed spread UNCE, Reno, Nev.

  5. Weed impacts • Decreased grazing potential • Economic losses from refusals of hay shipments • Decreased crop yields • Cost of control UNCE, Reno, Nev.

  6. Weed impacts • Decreased property values • Loss of wildlife and fish habitat • Impairment of wetland functions • Increased erosion • Toxicity UNCE, Reno, Nev. • Damaging to the economy or environment • Difficult to control • Dominate sites Three D’s

  7. How weeds grow • Dicot (Broadleaf) • Two true leaves • Broad leaves have net-like veins • Coarse tap root • Monocot • (Grass) • One seed leaf • Parallel veins • Fibrous roots

  8. Monocot Vs Dicot

  9. Plant life cycles • Annual • One season for all stages of development • Produce foliage, flower seeds, then die • Summer annuals • Live from spring to fall • Examples: • foxtail, pigweed • Winter annuals • Germinate in fall and winter • Examples: • cheatgrass and mustard UNCE, Reno, Nev. Yellow starthistle

  10. 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

  11. 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

  12. 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.

  13. Identifying weeds Plant parts for broadleaf identification NRCS, Bozeman, Mont.

  14. Have you correctly identified the weed? Spotted knapweed Tumble mustard Dandelion Yellow starthistle

  15. 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.

  16. How do weeds ensure their success? • They are persistent • Will return year after year • Reproduce vigorously • Spread seeds effectively UNCE, Reno, Nev.

  17. 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.

  18. 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

  19. 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

  20. Hand removal of weeds UC Davis Sticky traps and other physical traps/barriers

  21. 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

  22. Building a weed management plan CONSIDER 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.

  23. 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

  24. Method 1 of IWM:Prevent the invasion and spread of weeds • Minimize soil disturbance and bare ground • Don’t overgraze pastures • Apply the appropriate amount of water • Avoid driving in weed- infested areas USDA NRCS

  25. 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

  26. 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

  27. Method 3 of IWM: Mechanical Control • Cultivation • Hoeing • Bulldozing • Burning • Hand pulling • Mowing UNCE, Reno, Nev. • Mulching • Solarizing (use clear plastic for maximum affect) • Repeated tillage can help reduce seed populations CSUCE UNCE, Reno, Nev.

  28. 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

  29. 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 weed UNCE, Reno, Nev.

  30. 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. NDOA Leaf eating beetle (Diorhabda elongata) on tamarisk

  31. Tamarisk biocontrol NDOA http://www.tamariskcoalition.org/

  32. Method 6 of IWM:Chemical control UNCE, Reno, Nev. CSUCE

  33. Herbicides Managed grazing Prevention Dense vegetation, no bare spots Proper fertility and species USDA NRCS Manage pastures to minimize weeds

  34. Pesticides: an all-inclusive term for all “cides” Naming herbicides • Herbicide • Fungicide • Insecticide • Rodenticide • … • Chemical name • N-(phosphonomethyl)glycine • Common name • Glyphosate • Trade or brand name • RoundUp, Aquamaster, Glypro, Rodeo, etc. • Brand • Monsanto www.scotts.com

  35. To spray or not to spray?Consider: • Toxicity • Safety • 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

  36. Twelve steps to follow before using herbicides: • Identify the weeds • Determine their life cycles • Consider all control alternatives • Select the chemical based on effectiveness, safety, and price • Read the label carefully and make sure the herbicide is labeled for the pest and the site • Determine the best time to apply the chemical

  37. Twelve steps to follow before using herbicides: • Is the chemical restricted-use-only? • Consider proximity to water, nearby trees or shrubs, soil composition, tendency to contaminate water supplies • Check the weather • Have you read the MSDS? • Are you applying the appropriate amount by the best method? • Do you understand all safety requirements, and have you followed them carefully? (PPE)

  38. Less toxic More toxic Pesticide toxicity • Caution • Warning • Danger

  39. 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

  40. Chemical control • Selective • Kills only a specific plant or type of plant • Most common types are broadleaf vs. grass USDA NRCS • Examples of selective herbicides • 2,4-D (Weed-b-Gone, Weedar 64) • picloram (Tordon, retricted use, persistent) • chlorsulfuron (Telar, Glean) • triclopyr (Garlon 3A) ALWAYS READ AND FOLLOW THE LABEL DIRECTIONS!

  41. Nonselective herbicides • Kills most or all of the vegetation in the area covered • May be pre-mergent or postemergent chemicals • Examples of nonselective herbicides • glyphosate (Roundup) • imazapyr (Arsenal; use pre-emergence or postemergence; has a long residual in high pH soil) ALWAYS READ AND FOLLOW THE LABEL DIRECTIONS!

  42. 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.

  43. 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

  44. Successful weed management requires constant vigilance and care on the part of the land manager. CSUE

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