Weeds Commonly Found in Sugarcane Curtis Rainbolt EREC-Belle Glade

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 Ecosystems 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 Nutsedge Leaf Characteristics 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 Root system 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.)