Transcript Curtis Rainbolt EREC

Weeds Commonly Found in
Sugarcane
Curtis Rainbolt
EREC-Belle Glade
What Are Weeds?
Plant out place
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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
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Why Weed ID?
Weeds are prominent pests in crops
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Control methods almost always required
Mechanical
➔ Cultural
➔ Chemical (herbicides)
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Also important pests of natural areas
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Invasive weeds
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Brazilian pepper, old world climbing fern, Australian
pine, etc.
Impact of Weeds
Economic
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Reduced yields of crops
➔ Reduced quality of turf
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Ecosystems
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Crowd out native species
➔ Reduced habitat quality for all species
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Both plants and animals
How Do Weed Cause Harm?
Competition for:
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Light
➔ Nutrients
➔ Water
➔ Space
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Identification
Vegetative parts of grasses often
used to aid in identification:
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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
Diagnostic Grass
Structure
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Primary leaf
structures used to ID
grass
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ligule
auricle
collar
sheath
Vegetative
Characteristics
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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
• 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:
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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
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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
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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
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Wide leaves with wavy margins
Round stems
Usually dark green in color
Very similar to alexandergrass
Broadleaf panicum
Alexandergrass
(Brachiaria plantaginea)
– Relatively prostrate growth
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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
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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
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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
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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.)