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Transcript
Weed Management in the Landscape Calvin Odero Everglades REC Belle Glade Outline • Weeds – Weed classification, ID diagnostics • Weeds and landscapes • Lawns and turf – New – Established • Landscape ornamentals What is a weed? • Common definitions: – Plant growing where it is not wanted – Plant out of place – Plant that is a nuisance – Plant whose virtue has not been discovered – Plant that is objectionable or interferes with the activities or welfare of man (WSSA) Weeds and landscapes • Weeds are usually the most visible of landscape pests • Weeds are of concern principally because − Compete with desirable plants − Destruct the appearance and function of landscapes • Aesthetically unappealing • Weeds can harbor insect and disease pests • May pose a health hazard to humans – poison ivy, common ragweed Weeds and landscapes • Other harmful aspects of weeds – Increase the cost of site preparation – Increase the cost of maintenance – Increase the cost of protection Weed classification • Phylogenetic relationships – Ancestry, ancestral similarities • Habitat – Cropland, rangeland, aquatic, environmental, parasitic, landscape • Type of plant – Broadleaf, grass, sedge • Life history – Annual, biannual, perennial Weed identification • Proper identification and understanding of growth habits of weeds are important – Determine weed vulnerabilities – Important step towards control • Identification of the best management strategies – Selection of effective control method, ex. herbicides , application timings Grass weed diagnostics • One cotyledon or seed-leaf • Leaf blades are long, narrow, alternate with parallel veins • Leaf sheath encircles the stem • Junction of leaf blade with sheath is the collar • Ligule (projection at base of leaf blade) • Auricles (claw-like projections at the leaf collar that partially encircle the stem) Smooth crabgrass (Digitaria ischaemum) • Very wide first leaf • Initial clumping growth progressing to prostrate, tillering • Visible membranous ligule • Hairless • Inflorescence – 2-6 fingerlike branches Southern crabgrass (Digitaria ciliaris) • Seedling – Hairy leaves, sheath, and collar • Upper leaves occasionally hairy on upper surface only • Membranous ligule • Infloresence – 2-9 fingerlike branches Bermudagrass (Cynodon dactylon) • Easy to identify – – – – Small leaves Rhizomes and stolons Mat forming Ligule fringe of short hairs (hard to see) • Produces seed and spreads vegetatively Goosegrass (Eleusine indica) • Low growing – Very white, stems flattened – Looks like it has been stepped on – Ligule uneven, membranous Grass-like plants Spreading dayflower Doveweed Broadleaf weed diagnostics • Two cotyledons or seed leaves (dicots) • Leaves have netlike veins (wider than grasses) • True leaves develop above cotyledons • Leaves have a petiole (leaf stalk) or may be sessile (without a petiole) • Leaves alternate or opposite • Stem erect, viny or twining, prostrate Broadleaf weeds Persian speedwell Spiny sowthistle Brambles Annual sowthistle Common groundsel Hairy bittercress Smooth bedstraw Hyssop spurge Carolina geranium Garden spurge Prostrate spurge Yellow woodsorrel Sedge diagnostics • • • • 3-angled stems Leaves arranged in threes Long grass-like leaves Propagation primarily by tubers Sedges Yellow nutsedge • A - sharp or needle like tip • Tubers produced at end of rhizomes Purple nutsedge • B - boat shaped tip • Tubers produced along the length of rhizomes A Yellow nutsedge B Purple nutsedge Weed identification • Weed ID manuals feature – Small & mature weeds, flowers, fruit characteristics – http://erec.ifas.ufl.edu/weeds/index.html Weeds and landscapes • Control can be difficult due to complexity of many plantings − More than one species planted − Mix of annual and perennial ornamentals • Requires a variety of weed management options Weeds and landscapes • To plan for an existing planting or after an installation is in place, consider − Type of plants present • Woody plants can tolerate herbicides that would injure an herbaceous plant − Weeds present and their lifecycles – Public concerns • Use of herbicides – Effect of herbicide runoff on water quality Weeds and landscapes • Because of the many variables, weeds in landscape plantings are usually controlled by − Combination of nonchemical and chemical methods • A balanced weed management plan requires an integrated approach Weeds and landscapes • Integrated approach would include – Prevention – Sanitation – Hand weeding – Mulching – Mowing – Cultivation – Use of herbicides Lawns and turf • Turf areas include home lawns, commercial lawns, golf courses, parks, recreational areas, roadsides • Management practices produce a strong and vigorous turf – Choice of adapted lawn grass species, proper grading and seed bed preparation, fertilization, mowing, watering, pest control New lawns • Before planting – Cultivation – Herbicides with no residual toxicity to the turf to be seeded or sodded later • Glyphosate, glufosinate • After planting – Mowing – Herbicides • Low rates of growth regulator herbicides to avoid injury (1/4 – 1/2X rates) • Rates can gradually increase as grass becomes established Established lawns • Grasses have developed extensive root system, well tillered, rhizome system (runner) well developed • Properly manage turf to produce a dense, healthy, actively growing stand – Good management • Weeds can be controlled by hand pulling or cutting – Symptom of poor management • Large weed populations Established lawns • Proper management – Mowing height, mowing frequency, adapted species, fertilization, irrigation, thatch management • If weeds become a problem, there are many herbicides that may be used • Established turf tolerates herbicides much better than new planting Established lawns: herbicides • Soil-active (PRE) and foliar-active (POST) • PRE – applied 2-3 weeks before weed seed germination – Require immediate overhead irrigation/rainfall • POST – emerged weeds – Effective if weeds have active growth and not stressed – Check herbicide rainfast before application Established lawns: herbicides • Tolerance of turfgrass species differ • Many commercial formulations contain two- and three-way mixes – Provide a wide spectrum of weeds • Lawn fertilizers are formulated with broadleaf and grass herbicides Grass control • POST control in tolerant species through single/repeat applications of organic arsenicals – MSMA (Fertilome, Dallisgrass Killer) – 2-4 applications at 7-10 days required for complete control – Rate, number of applications increase as weeds mature • POST control of grassy weeds in centipedegrass – Sethoxydim (Vantage) – Atrazine-containing materials (Scotts Bonus Type S, Hi-Yield) • Provide good control of young grassy weeds with the added benefit of controlling many young broadleaf weeds Broadleaf control • Controlled with – Phenoxy (2, 4-D, MCPA, mecoprop) – Benzoic acid (dicamba) • Selective, systemic, foliar-applied herbicides • Few broadleaf weeds, especially perennials, are controlled with just one of these herbicides • These materials are commonly found in three-way herbicide mixtures – – – – Trimec Ortho's Weed-B-Gon Spectracide Weed Stop Repeat applications at 10-14 days apart necessary for satisfactory weed control Sedges • Thrive in soils that remain wet for extended periods of time – Poor drainage – Excessive irrigation • The first step in nutsedge control – No overirrigation – Provide surface and subsurface drainage Sedge control • Repeat applications of the organic arsenicals (MSMA) – Effective but treatments are slow to kill the weeds, repeat applications are necessary, will result in extensive damage to certain turf species • Selective control – Bentazon (Basagran T/O, Hi-Yield Basagran) • Contact, complete coverage necessary for better bentazon efficacy • Regrowth will normally occur from roots and tubers • Repeat applications necessary – Halosulfuron (Manage) – Imazaquin (Image) • Repeat applications, possibly over several years, required to control all the underground reproductive parts or purple nutsedge. Landscape ornamentals • Balanced weed management program requires an integrated approach – Prevention, sanitation, hand weeding, mulching, cultivation, use of herbicides • Herbicides may have a lesser role with a balanced approach to weed management Prevention and sanitation • Establishing plants in a weed-free environment is critical to long-term success • Exclude weed introduction – Contaminated potting soil – Contaminated stock plants • • • • Never allow weed seed production Scout to identify infestations Removal of containers with perennial weeds Disposal of pulled weed biomass Cultivation • Manual – Tedious, expensive, but occasionally necessary • Mechanical methods – – – – Rototilling Disking Plowing Hoeing • Care must be employed to avoid physical damage to valuable plants during weed removal Mulching • Very effective method of weed control • Mulching the soil surface – Reduces light necessary for germination – Presents a physical barrier to emergence – Moisture retention – Soil stabilization – Enhanced aesthetics – Reduction in the need for herbicides Mulching • Natural organic – Composted yard wastes or animal wastes, grain straw, peat moss, pine straw – Wood chips, hardwood bark, softwood bark – Placed 2-3 inches or greater depths • Natural inorganic – Sand, pebbles, stones, shale – Require plastic mulch on soil surface beneath them or use of herbicide • Synthetic materials – Polyethylene or woven synthetic fabric – Prevent weed seeds from germinating Use of herbicides • PRE and POST • Wide variety of tolerance to herbicides • Non-selective herbicides ideal for brick walks, along landscape bed borders, under woody ornamentals • ALWAYS READ THE HERBICIDE LABEL – IT IS THE LAW Contact Information Telephone: 561-993-1509 Email: [email protected] References • Weed management in landscapes http://www.ipm.ucdavis.edu/PDF/PEST NOTES/pnweedmanagement.pdf • Weed management in landscapes http://cecalaveras.ucdavis.edu/weed.htm • Weed control in gardens and landscapes http://www.hort.purdue.edu/ext/ho-217.pdf • Weed Control Options in Landscape Beds and Groundcovers http://www.ctahr.hawaii.edu/oc/freepubs/pdf/L12.pdf