Weed identification and common weeds associated with sugarcane

Calvin Odero

Everglades RECBelle Glade, FL

Weed classification

• Weeds come in all growth forms• May be classified as

– Grass– Grass-like (sedge)– Broadleaf

• Forbs• Succulents• Shrubs

Monocots

Dicots

Weed classification: life cycles

Annuals- reproduce by seed only Biennial:

Life cycle completed in two years Flowering and fruiting in second year Examples: wild carrot, cudweed

Perrenials: Simple- reproduce by seed only Creeping- reproduce by seed and vegetative

propagules

Grass identification: vegetative parts

• Leaf blade, blade margin• Collar margin• Midrib• Ligule - structure which

occurs in grasses at point where the leaf sheath and blade meet

• Auricle - projections where sheath and blade meet

• Sheath margins - split with overlapping margins or united

Auricle variations

Ligule variations

Sheath variations

Steps 1 to grass ID

• Overall characteristics– Relative length and

width of first leaf– Seed characteristics

Step 2 to grass ID

• Stem Type– Round– Flat– Triangular

Step 3 to grass ID

• Ligule Type– Absent– Hairy– Membranous

Step 4 to grass ID

• Blade Type– Hairy or not (glabrous)– Midrib prominence and

color– Margin characteristics– Presence of auricles

Step 5 to grass ID

• Sheath margins– Split with overlapping

margins– United– Margin with hairs or

not

Step 6 to grass ID

• Root systems– Perennial with

creeping rhizomes– Annual

Monocots: grasses and sedges

Grasses Sedges (Grass-like)

Stems • Hollow or flattened• Occasionally solid• Nodes (jointed)

• Solid• Triangular (3-sided)• Without nodes

Leaves • Parallel veins• 2 sides

• Parallel veins• 3 sides

Flowers • Small• Inconspicuous

• Small• Inconspicuous

Example • Fall panicum • Yellow nutsedge

Yellow vs purple nutsedge

• Yellow

(Cyperus esculentus)– Leaves gradually taper

to a point– Flowers yellowish-

brown– Tubers smooth, round

shaped, at ends of rhizomes

• Purple

(Cyperus rotundas)– Leaves abruptly tapers

to a point– Flowers purple to

brown– Tubers rough, irregular

shaped, connected in chains

Purple vs yellow nutsedge

Fall panicum (Panicum dichotomiflorum)

• Most common grass in the area• Relatively easy to identify

– Stem can be hairy or smooth– Hairy when young– Ligule fringe of hairs– Round stem– Widely dispersed seedhead

Fall panicum (Panicum dichotomiflorum)

Goosegrass (Eleusine indica)

• Found in many fields• Low growing

– Very white, flattened stems

– Looks like it has been stepped on

– Probably not competitive

Crabgrass (Digitaria spp.)

• Very wide first leaf

• Initial clumping growth progressing to prostrate, tillering

• Visible membranous ligule

• Can be very hairy, or hairless, depending on species

Broadleaf panicum (Urochloa adspersa)

• Relatively prostrate growth– Wide leaves with wavy

margins– Round stems– Usually dark green in

color– Very similar to

alexandergrass

Broadleaf panicum (Urochloa adspersa)

Crowfootgrass (Dactyloctenium aegyptium)

• Plants glabrous, blade margins hairy

• Seed head like a crow foot

• Bends and roots at the lower nodes

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

Bermudagrass (Cynodon dactylon)

Sorghum (Sorghum almum)

• ‘Wild oat’• Closely related to

johnsongrass– No rhizomes– Large, membranous

ligule– Robust plant

Sorghum (Sorghum almum)

Torpedograss (Panicum repens L.)

• Perennial with robust, creeping, sharply pointed rhizomes

• Leaf blade stiff and erect

• Hairs on upper and lower leaf surface

• Seedheads with stiff, ascending branches

• Occurs in wet areas

Guineagrass (Panicum maximum)

• Some plants are extremely hairy, while others are hairless

• Small plants have narrow leaves

• Becomes very large• Highly branched

seedhead• Round stem

Napiergrass (Pennisetum pupureum)

• Very robust plant– Forms dense clumps

in fields– Long, wide leaves with

finely toothed margin– Up to 12 feet tall– Seedhead has “bottle

brush” appearance

Paragrass (Brachiaria mutica)

• Prostrate growing, medium size grass– Long stems covered

with hairs• Short hairs on leaf

surface

– Swollen nodes– Grows in very wet

areas• Often moves out of

ditches

– Pasture grass in Africa

Dicots: broadleaf plants

• Two cotyledons• Primary root often becomes a strong tap

root with smaller secondary roots• Leaves are usually net veined and broad

at the base with a petiole or stalk

Dicots: broadleaf plants

Forbs Shrubs Succulents

Stems • Solid• Pithy

• Solid • Growth rings

• Fleshy, thick• Sharp spines

Leaves • Net-veined • Net-veined • Small, fleshy• Seldom present

Flowers • Small or large • Colored• Showy

• Small• Showy

• Showy

Example • Common lambsquarters

• Lantana • Cacti

Broadleaf identification: vegetative parts

• Cotyledons - seed leaves

• First true leaf• Older leaves• Midvein• Leaf apex• Margin• Terminal bud

Steps 1 & 2 in broadleaf ID

• Overall appearance

• Shape of cotyledons

Steps 3 & 4 in broadleaf ID

• Leaf shape

• Leaf arrangement– opposite– alternate– whorled

• Root system

Spiny amaranth (Amaranthus spinosus)

• Most common‒ Large, upright growth

habit, entire leaves‒ Very evident spines

located at nodes

Livid amaranth (Amaranthus blitum)

• Can be prostrate or erect

• Notched leaf tips

Alligatorweed (Alternanthera philoxeroides)

• Common in wet areas of the EAA‒ Often spread by

cultivation‒ Low growing

• Hollow stems when growing in wet spots

• Opposite leaves• Small white blooms

Alligatorweed (Alternanthera philoxeroides)

Common lambsquarters (Chenopodium album)

• Common during the cooler months

• Can be difficult to control due to waxy leaf surface that leaves a white-gray color

Common purslane (Portulaca oleracea)

• Prostrate, succulent• Leaves small,

smooth, opposite or alternate

• Red stems• Small, yellow flowers

Common ragweed (Ambrosia artemisiifolia)

• Deeply dissected leaves

• Many hairs on upper and lower surfaces

• Long seedhead at top of plant

• Yellow/white flowers in multiples

Ragweed parthenium (Parthenium hysterophorus)

• Less common than common ragweed‒ Common along

canals, ditch-banks, noncrop areas

• Leaves less deeply dissected‒ Divisions don’t go all

the way to the stem

• White flowers‒ Single, not multiples

American black nightshade (Solanum americanum)

• Becoming more common in EAA‒ Alternate leaves

• Usually entire to somewhat lobed

‒ Purple fruit

Dayflower (Commelina spp.)

• Common in open areas, field edges– Small, probably not

competitive– Prostrate growth habit– Parallel veins on

leaves– Actually a monocot– Blue flowers

Sources of Weed ID Information

• Web Picture/Taxonomic Sites– Aquatic, Wetland and Invasive Plant

Particulars and Photographs (U. of Florida)• Excellent pictures and information• http://aquat1.ifas.ufl.edu/photos.html

– Weed Identification and Control in Southern Turfgrasses (U. of Georgia)

• Pictures, descriptions• http://www.griffin.peachnet.edu/cssci/TURF/turf.htm

• Southern Weed Science Society ID Guide

Sources of Weed ID Information

• Web Picture/Taxonomic Sites–Many, many more sites

• Many reputable sites– Many universities– Other public agencies

• Buyer beware– Some incorrect information on the web!

If you need help

• Actual plants are best– Store in plastic bag with damp paper towel

• 8 t0 10 hours

– Press between two pieces of paper• Change paper often while drying• Will last indefinitely

– Store on truck dashboard• PLEASE DON’T!

– Bring several plants• Flowers and seeds if possible• Different growth stages if possible

If you need help

• Pictures– Overall view (growth habit)– Specific characteristics

• Ligule (grasses)• Hair characteristics• Leaf shape• Root system

– Tubers, rhizomes, stolons

• Stem shape• Seeds or flowers if available• Other characteristics we looked at earlier

If you need help

• Additional information– What type of area

• Dry or wet• Sandy or muck• Cropped area, natural area, disturbed area• History of area (previous crops, etc)

– Actual location• County, nearby town/city/landmark

Take Home

• Weed ID can be challenging– Many resources available

• Web is very helpful

– When you need help:• Provide as much information as possible

– Quality plant sample– Identify important/unique characteristics– Site information (wet vs. dry, etc.)

Weed ID manuals

Contact Information

Calvin Odero

University of Florida-IFAS

Everglades Research & Education Center

3200 E Palm Beach Road

Belle Glade, FL 33430

561-993-1509

dcodero@ufl.edu