Fall Spray Day Weed Identification Calvin Odero Everglades Research and Education Center Belle Glade December 1, 2010
Outline Weed definition Weed classification Weed identification Grass weed diagnostics Grass weeds of row crops Broadleaf weed diagnostics Broadleaf weeds of row crops
What are weeds? Common definitions Plants growing where they are not wanted Plants out of place Plants which are a nuisance Plants whose virtues have not been discovered Plants that are objectionable or interfere with the activities or welfare of man (WSSA)
What are weeds? A native or introduced species that has perceived negative ecological or economic effect on agricultural or natural systems A plant is a weed because it has definable characteristics that set it apart from other species
Characteristics of weeds Abundant seed production Rapid establishment Seed dormancy Long term seed dispersal Adaptations for spread Vegetative reproduction Capacity to occupy disturbed sites
Weed classification 200 plant species are the most important world weeds Family Species Percent of total Poaceae (Grass) Cyperaceae (Sedge) 44 12 27% 43% Asteraceae (Sunflower) 32 Polygonaceae (Buckwheat) Amaranthaceae (Pigweed) Brassicaceae (Mustard) Fabaceae (Bean) Convolvulaceae (Morningglory) Euphorbiaceae (Spurge) Chenopodiaceae (Goosefoot) Malvaceae (Mallow) Solanaceae (Nightshade) 8 7 7 6 5 5 4 4 4 68% in 12 plant families
Weed classification Phylogenetic relationships Ancestry and ancestral similarities Habitat Cropland, rangeland, forest, aquatic, environmental, parasitic Life history Annual, biannual, perennial Type of plant Broadleaf, grass, sedge
Weed identification Manuals feature mature weeds, flowers, and fruit characteristics as an aid in identification Weeds must be controlled when small, before they flower or mature to prevent them from competing with the crop for Light Soil nutrients Soil moisture Space
Weed identification Knowing how to identify weeds then understanding their life cycles and vulnerabilities are important steps towards control Proper weed identification allows for identification of the best cultural strategies for control, and selection of effective herbicides and application timings
Weed identification Distinguishing between annuals, biennials, and perennials is the most compelling reason to learn weed identification as management strategies and herbicide effectiveness differ significantly between these categories
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)
Step 1 to grass identification Overall characteristics Relative length and width of first leaf Seed characteristics
Step 2 to grass identification Grass leaves are either rolled or flat within the stem Sedges can be identified by a triangular stem Rolled Flat Triangular
Step 3 to grass identification Some grasses have auricles Ligule may be absent or present Membrane Fringe of hair (hairy)
Step 4 to grass identification Blade type Hairy or glabrous (lacking hair) Midrib prominence and color Margin characteristics
Step 5 to grass identification Leaf sheaths may be Open, split and overlapping, closed (fused) Hairy or glabrous (lacking hair)
Step 6 to grass identification Root system Annual, with a simple, fibrous root system Perennial, producing rhizomes, rootstocks, or stolons
Grasses and grass-like seedling species: monocots (leaves have parallel veins, sheaths at the base clasp the stem) 1. Leaves generally broader.....spreading dayflower 1. Leaves narrow 2. Stems triangular (3-angled or sided), solid 3. Leaves gradually tapering to a sharp point.....yellow nutsedge 3. Leaves abruptly tapering to a sharp point......purple nutsedge 2. Stems roundish, hollow: 4. From fibrous roots, rhizomes, or stolons: 5. Leaves flat: 6. Leaves folded in the bud: 7. Ligule a fringe of hairs......bermudagrass 7. Ligule membranous.......goosegrass 6. Leaves rolled in a bud: 8. Ligule a fringe of hairs... fall panicum guineagrass crowfootgrass giant bristlegrass nappiergrass 8. Ligule membranous...almum sorghum southern crabgrass
Spreading dayflower (Commelina diffusa) Annual, creeping growth habit Seedling Leaves wider than grasses, rounded tip Later leaves much longer than wider Mature plant Stems, leaves are thick and fleshy Stem swollen at nodes, appearing jointed Leaves sessile, often hairy on upper and lower surfaces, margins smooth Roots fibrous, stems root at node Two large and one small blue petal Propagation by seed, vegetatively
Spreading dayflower
Nutsedges (Cyperus spp.) Perennial, 3-angled stems, leaves arranged in threes, long grass-like leaves Seedling small inconspicuous, rarely encountered Propagation primarily by tubers Yellow nutsedge Leaves yellow-green Leaves gradually tapering to a sharp point, midrib ends Tubers produced at end of rhizomes Yellowish-brown spikelet Purple nutsedge Leaves dark green Leaves abruptly tapering to a sharp point, midrib continues Tubers produced along the length of rhizomes Reddish-purple spikelet
Nutsedges (Cyperus spp.) Yellow nutsedge A - sharp or needle like tip B - Constriction 1/2 to 1 1/2 inches from tip C - Midrib groove absent or barely visible beyond constriction point (B) Purple nutsedge D - boat shaped tip E - without constriction at tip F - midrib groove continues to leaf tip C B Yellow nutsedge A F E D Purple nutsedge
Yellow nutsedge
Purple nutsedge
Bermudagrass (Cynodon dactylon) Perennial, mat forming, spreading rhizomes and stolons Seedling Ligule a row of hairs (hard to see) Blades smooth, slightly rough margins Sheath smooth Mature plant Leaves flat, ring of white hair around collar Blades smooth (with hair toward base), margins slightly rough Sheaths strongly compressed, smooth or with few hairs in the collar Hard, scaly rhizomes and flattened stolons 3-7 finger-like spikes radiating from a central point
Bermudagrass
Goosegrass (Eleusine indica) Annual, prostate, mat-like rosette with stems radiating from a central point Seedling Short membranous unevenly toothed ligule with cleft at center Blades smooth, strongly folded Sheath smooth, prominently compressed, light green to white at base Collar broad, hairless Mature plant Blades folded along midvein, smooth, occasionally sparsely hairy on both sides, rough margins Sheath loosely overlapping, smooth, whitish at base Collar broad, white, sparse hair at the edges Root system fibrous, does not root at nodes 2-6 spikes in clusters at top of stems, one spike below the others, Two rows of seed on underside of spikes
Goosegrass
Goosegrass
Fall panicum (Panicum dichotomiflorum) Annual with erect or spreading broadly from the base Seedling Ligule fringe of hairs First few leaves densely hairy only on lower surface Sheath densely hairy, rough margins Collars densely hairy Seedlings become less hairy with age, completely lack hairs at maturity Purplish coloration Mature plant Stems have waxy appearance, swollen and irregular lower nodes Blades smooth on both sides, dull above and glossy beneath Midrib prominent Sheaths smooth, purplish, slightly compressed Fibrous root system, stems root at nodes Freely branched, spreading panicle, may appear purplish at maturity
Fall panicum
Fall panicum
Guineagrass (Panicum maximum) Perennial, tufted grass, short, creeping rhizome Ligule hairy Leaf-blade surface glabrous, or pubescent (soft fine hair) Erect stems, root at nodes Sheath covered in fine hair (very hairy) Large multi-branched, open panicle, spikelets green to purple Very problematic
Guineagrass
Crowfootgrass (Dactyloctenium aegyptium) Annual, mat forming, above ground runners Seedling Ligule a fringe of hairs Blade and sheath glabrous (hairless) Margins with long stiff hairs Mature plant Blade smooth, margins with long stiff hair Sheath smooth, collar hairy 1-7 spikes, spikelets on lower side, seeds extend out in the shape of a claw (like crow s foot) Root fibrous
Crowfoot
Giant bristlegrass (Setaria magna) Annual with erect stems, up to 12 ft tall Seedling Ligule hairy Blade smooth to rough Sheath smooth Mature plant Blades flat, rough Sheaths smooth, but margins near top lined with hairs Joints smooth, distinctive ring of fine hairs below the joint Stem extremely flat Roots fibrous Seed head a panicle (cylindrical composed of bristles, yellowish-brown in color, and usually 3-12 inches long)
Giant bristlegrass
Nappiergrass (Pennisetum purpureum) Perennial with robust, erect, cane-like stems Seedling Ligule hairy Blade hairless to more or less hairy long stiff hair Sheath hairy Mature plant Blades flat, rough, long stiff hair on upper surface, rough or smooth on lower surface Sheath hairy at or near bottom of stem Stem round (unlike giant bristle grass) Seed head similar to bristly bottle brushes
Nappiergrass
Sorghum-almum (Sorghum almum) Perennial from short, thick, scaly underground runners Seedling Ligule membranous at the base, fringed at the top Blade hairless Sheath smooth, hairless Can look like sugarcane seedling when small Mature plant Blade rough, flat, prominent midrib, no hairs (except occasionally at base on upper leave surface) Sheath open, smooth except for a few hairs Open panicle composed of numerous whorled branches
Sorghum-almum
Sorghum-almum
Southern crabgrass (Digitaria ciliaris) Annual, tufted, prostrate to spreading Seedling Membranous ligule Stiff hairs on blade and sheath at right angle to plant surface Collar broad with long hairs at margin Mature plant Blades lack hair on both surfaces Sheaths compressed and hairy Tillering after 4-5 true-leaf, tiller nodes elongate Elongated stems root at nodes Older sheaths may turn dark red or maroon Seed head 3-5 (-13) spikes clustered at the top of stems
Southern crabgrass
Southern crabgrass
Broadleaf weeds diagnostics Leaves have netlike veins (wider than grasses) Two cotyledons or seed leaves (dicots) True leaves develop above cotyledons Shapes of cotyledons and first true leaves are important for identification 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 diagnostics
Steps to broadleaf identification Overall appearance Shape of cotyledons Leaf shape Leaf arrangement Root system
Broadleaf seedling species: dicots (leaves usually with branched veins) 1. Linear cotyledons 2. First true leaves alternate 3. First true leaves ovate, nick in the tip 4. Stems reddish at the base but later with spines at nodes...spiny amaranth 4. Stems reddish towards base and smooth to hairy. smooth pigweed 2. First true leaves opposite but later leaves alternate 5. Leaves succulent 6. Leaves egg-shaped and widest at tip, sessile, red tinged... common purslane 5. Leaves not succulent 7. Leaves egg-shaped and pointed at tip, mealy white coating... common lambsquarters 1. Spatulate cotyledons 8. First true leaves opposite, deeply cleft but later alternate....common ragweed 8. First true leaves opposite, egg-shaped, covered in fine hairs.....parthenium ragweed
Smooth pigweed (Amaranthus hybridus) Annual, erect with smooth branched stem Seedling Cotyledons linear First true leave ovate, nick at tip, alternate, less wavy margins Stems reddish and smooth to hairy Mature plant Erect and slender Upper stem densely hairy, hairs short Flowers green in dense clusters at tip of stems Reddish shallow taproot
Smooth pigweed
Spiny amaranth (Amaranthus spinosus) Annual, erect, very sharp, stiff spines Seedling Cotyledons linear First true leaf ovate, nick at tip Leaves with wavy margin Stems reddish with spins at nodes later Mature plant Erect with freely branching stem Stem has pair of sharp spines at base of leaves Flowers green in dense clusters at tip of stems Reddish taproot
Spiny amaranth
Common purslane (Portulaca oleracea) Annual Seedling Cotyledons linear First true leaf egg-shaped and widest at tip (obovate) Leaves succulent, obovate, sessile, red tinged Stem prostrate, reddish Mature plant Stems much branched, purplish-red or green, smooth, completely prostrate, or turned up at ends Leaves opposite or alternate, thick, fleshy, smooth untoothed margins Blade spatulate, sessile Yellow clustered flowers at end of stem Thick taproot, fibrous secondary root
Common purslane
Common lambsquarters (Chenopodium album) Annual Seedling Cotyledons linear First true leaf lanceolate to ovate Leaves wavy or toothed and have gray-mealy coating First pair opposite, all other leaves alternate Stem covered in mealy-white granules Mature plant Stems erect, branching, hairless, vertically ridged, often with maroon stripes Leaves petioled, egg-shaped, irregularly toothed White-mealy coating on younger leaves Upper leaves are sometimes linear, sessile, may have entire margins Short and branched taproot Panicle arising from end of stems or leaf axils, individual flowers inconspicuous
Common lambsquarters
Common ragweed (Ambrosia artemisiifolia) Annual Seedling Cotyledons thick, spatulate Leaves opposite becoming alternate by the fourth node Blades hairy on upper surface and margin, densely hairy on underside Leaves deeply cleft on margins, forming rounded or slightly pointed lobes Mature plant Stems erect, branched, rough hairs Leaves hairy to nearly smooth Blades compound (pinnatifid) Leaves alternate, sometimes lower leaves opposite Shallow fibrous root Flower head small, green, inconspicuous, produce large amounts of pollen
Common ragweed
Ragweed parthenium (Parthenium hysterophorus) Annual Seedling Rounded paddle shape cotyledon First true leaves are egg-shaped, covered in fine, white hairs Older leaves become increasingly lobed and deeply divided Basal rosette Mature plant Leaves alternate, compound, lower leaves forming basal rosette, upper leaves entire to lobed (deeply divided), short hair on both sides Stem erect to branched Taproot White disked flowers
Parthenium ragweed
If you need help Collect actual plants Store in plastic bag with damp paper towel 8-10 hours Press between two pieces of paper Change paper often while drying Will last indefinitely Please don t store on truck dashboard Bring several plants Different growth stages if possible
If you need help Pictures Overall view (growth habit) Specific characteristics Ligule (grasses) Hair characteristics on leaves, stems Leaf shape Root system Fibrous, taproot, tubers, rhizomes, stolons Stem shape Seeds or flowers if available Other characteristics we looked at earlier
If you need help Additional information to collect Location Dry or wet Sandy or muck Cropped area, natural area, disturbed area Cropping history Actual location County, nearby town/city/landmark
Sources of weed ID information Picture books Southern Weed Science Society Weed ID Guide Excellent resource Weeds of Southern Turfgrasses (UF, IFAS) Wildflower books Good for plants with prominent flowers Area-specific books Many exist Varying quality of information
Sources of weed ID information Web Picture/Taxonomic Sites Aquatic, Wetland and Invasive Plant Particulars and Photographs (UF, IFAS) Excellent pictures and information http://aquat1.ifas.ufl.edu/photos.html Many, many more sites Many reputable sites Many universities Other public agencies Beware Some incorrect information on the web!
Take Home Message Weed ID can be challenging, get help from UF extension faculty Many resources available Web is very helpful When you need help Provide as much information as possible Quality plant sample Identify important/unique characteristics Location information
Contact Information Calvin Odero Office Wedgworth Building Room 155 Telephone 561-992-1336 (Office) Email dcodero@ufl.edu