Introduction To Weed Science And Weed Identification

Introduction to Weed Science andWeed Identification

Definition of a Weed A plant growing where it is not wanted (Oxford Dictionary) Any plant or vegetation, excluding fungi, interfering withthe objectives or requirements of people(European Weed Science Society) A plant that is especially successfulat colonizing and proliferating indisturbed sites

First Steps in Weed Management To effectively manage weeds youshould know:– What weed you are dealing with –correct identification– Consider impact of the weed– Life cycle of the weed Weed biology influences methods andoptimum time for managementstrategies

Weed Classification Morphology– Structure and form Life cycle– How it developsGround ivyYellow foxtailYellow nutsedge

Weed Classification – Morphology Monocotyledon – onecotyledon or oneembryonic leaf– Grasses, sedges, rushes Dicotyledon - twocotyledons– “Broadleaf” plants

Weed Classification – Life Cycle Annuals– Complete their life cyclefrom seed to seed in lessthan 12 monthsGiant foxtailVelvetleafCocklebur

Summer Annuals Seeds germinate in spring Flower in mid to latesummer Produce seed in latesummer or fall, then die Similar growing season tocorn and soybean E.g., lambsquarters,foxtails, crabgrass,purslane, waterhempLambsquartersLarge crabgrass

Winter Annuals Germinate in late summeror fall Dormant over winter Flower and produce seedin mid to late spring Die in summer E.g., shepherd’s purse,chickweed, pennycress,speedwellsPennycressChickweed

Biennials Complete life cycle intwo years Germinate and formbasal rosette first year,remain vegetative andstore food for winterWild carrotMusk thistleWild parsnip

Biennials Flower, produce seed, and dieduring second growing season Need undisturbed soil for atleast two years E.g., musk thistle, wild carrot,wild parsnip, garlic mustardWild carrotMusk thistleWild parsnip

Perennials (herbaceous) Live for more than two years– Simple: produce a taproot,spread only by seed E.g., Dandelion, broadleafplantainBroadleaf plantain– Creeping: can reproduce bybuds, rhizomes, tubers,bulbs, and seed E.g., Quackgrass, nutsedge,leafy spurgeYellow nutsedge

Weed ID - Sources of Information ISU Weed Identification Field GuideReference booksExtension bulletinsMany websites– http://www.wssa.net/Weeds/ID/PhotoGallery.htm– http://plants.usda.gov/ Someone “in the know”– Local experts– Extension offices

What Makes a Weed Successful? Seed characteristics Ability to germinate andgrow in many environments Rapid seedling growth Self-compatibility or easycross-pollination Vigorous vegetativereproduction Ability to tolerateenvironmental stressesProstrate spurgeCanada thistle

Seed Characteristics Longevity of seedLong period of seed productionHigh seed outputAbility to produce seed inadverse conditions Long and short seed dispersalGiant ragweedLambsquarters

Vegetative Reproduction Rhizomes– Underground structures thatproduce new plants E.g., canada thistle, quackgrass Stolons– Above-ground creeping stemsthat root at nodes andproduce new plants E.g., ground ivy (creepingcharlie)QuackgrassGround ivy

Vegetative Reproduction Bulbs, bulblets, tubers– Underground leaf tissuemodified for foodstorage. Produces newplants E.g., wild garlic, yellownutsedgeYellow nutsedge– Aerial bulblets (aboveground) E.g., wild onion, wild garlicWild onion

Vegetative Reproduction Plant reproduction– Each plant part canregenerate anotherplant– When cultivating, theimplement canredistribute them in thefield E.g., Asiatic dayflower,purslaneAsiatic dayflowerPurslane

Dispersal WindAttachment – burs, thorns, stickersDandelionBirds – digestion/excretionArtificial dispersal – “humandispersal”– Soil and compost– Equipment– Plants– Contaminated seedBurdock

Weed Management StrategiesCanada thistleVelvetleafPoison ivyYellow nutsedge

Summary Identify the weed Know the life cycle Use control strategies based onweed species, life cycle, crop, fieldor landscape situation, and theenvironment

Introduction to Weed Science and Weed Identification . Definition of a Weed A plant growing where it is not wanted (Oxford Dictionary) Any plant or vegetation, excluding fungi, interfering with the objectives or requirements of people (European Weed Science Society)