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Weeds Commonly Found in Sugarcane

What Are Weeds?

➔Plant out place➔ Using this definition, almost any plant can be a

weed➔ Melaleuca--native tree in Australia, but weed in south

Florida➔ Corn--crop when it is planted, but weed when

volunteer plants come up the next year➔ Most “weeds” are non-cultivated native or non-native

plants

Why Weed ID?

➔Weeds are prominent pests in crops➔ Control methods almost always required

➔ Mechanical➔ Cultural➔ Chemical (herbicides)

➔Also important pests of natural areas➔ Invasive weeds

➔ Brazilian pepper, old world climbing fern, Australian pine, etc.

Impact of Weeds

➔Economic➔ Reduced yields of crops➔ Reduced quality of turf

➔Ecosystems➔ Crowd out native species➔ Reduced habitat quality for all species

➔ Both plants and animals

How Do Weed Cause Harm?

➔Competition for:➔ Light➔ Nutrients➔ Water➔ Space

Identification

Vegetative parts of grasses often used to aid in identification:➔ 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

Diagnostic Grass Structure

➔ Primary leaf structures used to ID grass

➔ ligule➔ auricle➔ collar➔ sheath

Vegetative Characteristics

• Blade

• Midrib• Ligule• Collar• Sheath• Auricle

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

Differences between grasses and sedges:• Sedges have a solid, triangular in cross

section, stem. Leaves are arranged in threes (extend in three directions).

• Grass stems may be round or flattened.

Purple vs Yellow NutsedgeLeaf Characteristics

• Purple– A - boat shaped tip– B - without constriction at tip– C - midrib groove continues to

leaf tip

• Yellow– D - sharp or needle like tip– E - Constriction 1/2 to 1 1/2

inches from tip– F - Midrib groove absent or

barely visible beyond constriction point (E)

Purple vs Yellow Nutsedge

Purple vs Yellow Nutsedge

Vegetative parts of broadleaf weeds often used to aid in identification:

• cotyledons - seed leaves

• first true leaf

• older leaves

• midvein

• leaf apex

• margin

• terminal bud

Dicots: Broadleaved plants

– 1. Two cotyledons

– 2. Primary root often persists to become a strong tap root with smaller secondary roots.

– 3. Leaves are usually net veined and are usually broad at the base with a petiole or stalk usually present

Diagnostic Broadleaf Structure

• Cotyledon

• Leaf– midvein– margin– shape– arrangement

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

Common Sugarcane Weeds

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)

Wild oats (Sorghum almum)

• Not really an oat– Closely related to johnsongrass

• No rhizomes• Large, membranous ligule• Robust plant

– Can look like sugarcane seedling when small– Do we identify it correctly early?

Wild Oats (Sorghum almum)

Broadleaf panicum

• Panicum adspersum (Urochloa adspersa)– Relatively prostrate growth

• Wide leaves with wavy margins• Round stems• Usually dark green in color• Very similar to alexandergrass

Broadleaf panicum

Alexandergrass (Brachiaria plantaginea)

– Relatively prostrate growth• Somewhat wide leaves with straight margins• Round stems• Usually light green in color• Very similar to broadleaf panicum

– leaves narrower (usually)– margins straight rather than wavy (usually)

Alexandergrass (Brachiaria plantaginea)

Alexandergrass vs Broadleaf panicum

Guineagrass (Panicum maximum)

• Very problematic if you have it– Small plants have narrow leaves

• Stems, sometimes leaves very hairy

– Becomes very large– Highly branched seedhead– Round stem– Can look similar to Sorghum almum

• Sorhum almum shouldn’t be hairy

Guineagrass (Panicum maximum)

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

Napiergrass(Pennisetum pupureum)

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

Paragrass (Brachiaria mutica)

Bermudagrass (Cynodon dactylon)

• Very common – Easy to identify

• Small leaves• Rhizomes and stolons• Matt forming• Ligule fringe of short hairs (hard to see)

Bermudagrass (Cynodon dactylon)

Goosegrass (Elusine indica)

• Found in many fields

• Low growing– Very white, flattened stems– Looks like it has been stepped on– Probably not competitive

Goosegrass (Elusine indica)

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

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.

Spiny pigweed (Amaranthus spinosus)

• Most common pigweed species– Stickerweed

• Large, upright growth habit, entire leaves

• Very evident spines located at nodes

Spiny pigweed (Amaranthus spinosus)

Alligatorweed (Alternanthera philoxeroides)

• Common in many areas of the EAA– Prefers wet areas– 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 some years– Usually during the cooler months (Dec, Jan)– Can be difficult to control

• Waxy leaf surface– Small “dots” of wax are useful for ID– Gives leaves a white-gray color

• Alternate leaves• Medium size lobes on leaves

Common lambsquarters (Chenopodium album)

Common purslane(Portulaca oleracea)

• Very common– Probably not competitive– Prostrate growing– Succulent– Leaves small, smooth, opposite or alternate– Small, yellow flowers– Red stems

Common purslane(Portulaca oleracea)

Common ragweed(Ambrosia artemisiifolia)

• Often found on ditch banks and field edges– Deeply dissected leaves– Many hairs on upper and lower surfaces– Long seedhead at top of plant

• Yellow flowers

– Similar in appearance to ragweed parthenium• Different flower type

Common ragweed(Ambrosia artemisiifolia)

Ragweed parthenium(Parthenium hysterophorus)

• Primarily ditchbanks– Less common than common ragweed– Leaves less deeply dissected

• Divisions don’t go all the way to the stem

– White flowers• Single, not multiples

Ragweed parthenium(Parthenium hysterophorus)

Dayflower (Commelina spp.)

• Common in open areas, field edges– Small, probably not competitive– Prostrate growth habit– Parallel veins on leaves

• Actually a monocot, not a dicot

– Blue flowers

Dayflower (Commelina spp.)

American black nightshade(Solanum americanum)

• Occasional weed in EAA– Problematic in vegetables (tomato, pepper)

• Same family (Solanaceae)• Resistant to paraquat in some areas

– Alternate leaves• Usually entire to somewhat lobed

– Purple fruit– Seems quite competitive

American black nightshade(Solanum americanum)

Sources of Weed ID Information

• Picture books:– Wildflower books

• Good for plants with prominent flowers

– Area-specific books• Many exist

– Varying quality of information

– Southern Weed Science Society ID Guide• Excellent resource

– Very thorough (almost to many plants)

Sources of Weed ID Information

– “Simple” keys– Many for specific crops or areas

– Helpful in crops where common weeds are limited– Not so helpful in natural/disturbed areas

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

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!

So You’re Stumped!• If you need help:

– Actual plants are best• 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

• Store on truck dashboard– Please don’t!

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

So You’re Stumped!

• 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

So You’re Stumped!

• 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.)