Transcript Slide 1
Developed by: Susan Donaldson University of Nevada Cooperative Extension UNCE, Reno, Nev. 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 What’s a weed? USDA-ARS Invasive weed spread Weed 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. Decreased grazing potential Economic losses from refusals of hay shipments Decreased crop yields Cost of control UNCE, Reno, Nev. Decreased UNCE, Reno, Nev. property values Loss of wildlife and fish habitat Impairment of wetland functions Increased erosion Toxicity Damaging to the economy or environment Difficult to control Dominate sites 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 Annual ◦ ◦ Summer annuals ◦ ◦ One season for all stages of development Produce foliage, flower seeds, then die Live from spring to fall Examples: ◦ foxtail, pigweed Winter annuals ◦ ◦ Germinate in fall and winter Examples: ◦ cheatgrass and mustard UNCE, Reno, Nev. Yellow starthistle 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 Perennials ◦ ◦ ◦ Live more than two years Will produce foliage, seed, and reach maturity each year Examples: perennial pepperweed Canada thistle UNCE, Reno, Nev. Dandelion 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. NRCS, Bozeman, Mont. Spotted knapweed Tumble mustard Dandelion Yellow starthistle 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. They are persistent ◦ ◦ ◦ Will return year after year Reproduce vigorously Spread seeds effectively UNCE, Reno, Nev. They are harmful ◦ ◦ ◦ ◦ ◦ UNCE, Reno, Nev. ◦ Can alter the site they grow in by accumulating salts, changing water table depths, increasing erosion, increasing wildfire frequency, Etc. UNCE, Reno, Nev. Natural means ◦ ◦ ◦ Wind Water Animals Humans ◦ ◦ ◦ ◦ ◦ ◦ ◦ Irrigation Roadside shoulder work Construction/ fill dirt Vehicles Tillage Contaminated seed or feed Livestock management 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 Hand removal of weeds UC Davis Sticky traps and other physical traps/barriers Planning Setting action thresholds Monitoring and detection Identification Implementation Evaluation Prevention Eradication Mechanical controls Cultural controls Biological controls Chemical controls 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. 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 weedinfested areas USDA NRCS 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 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 Cultivation Hoeing Bulldozing Burning Hand pulling Mowing Mulching Solarizing (use clear plastic for maximum affect) Repeated tillage can help reduce seed populations UNCE, Reno, Nev. CSUCE UNCE, Reno, Nev. Cultural control involves using land management tools that make it difficult for weeds to be successful ◦ Shading ◦ Water and nutrient management ◦ Correct seeding rates 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. 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 http://www.tamariskcoalition.org/ NDOA UNCE, Reno, Nev. CSUCE Herbicides Managed grazing Prevention Dense vegetation, no bare spots Proper fertility and species USDA NRCS Herbicide Fungicide Insecticide Glyphosate Trade or brand name ◦ N-(phosphonomethyl)glycine Common name ◦ Rodenticide … Chemical name ◦ RoundUp, Aquamaster, Glypro, Rodeo, etc. Brand ◦ Monsanto www.scotts.com 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 1. 2. 3. 4. 5. 6. 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 7. 8. 9. 10. 11. 12. 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) Caution Less toxic Warning Danger More toxic Interfere with or disrupt biochemical or physiological processes in susceptible plants Often affect a specific enzyme or reaction Example: amino acid inhibitors - glyphosate Selective ◦ ◦ Kills only a specific plant or type of plant Most common types are broadleaf vs. grass Examples 2,4-D of selective herbicides (Weed-b-Gone, Weedar 64) picloram (Tordon, retricted use, persistent) chlorsulfuron (Telar, Glean) triclopyr (Garlon 3A) ALWAYS READ AND FOLLOW THE LABEL DIRECTIONS! USDA NRCS 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! 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. 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 CSUE