Unit 9: Basic Weed Scouting
Unit 9: Basic Weed Scouting
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Unit 9 Objectives:
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Knowledge of basic scouting procedures
Understanding of proper scouting times
Using field weed surveys
Basic weed ID
Unit 9: Basic Weed Scouting
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Early season weed scouting
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Done within 2 wks of planting after emergence
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Also can determine:
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Need for hoeing
– Preemergence & preplant herbicides
– Need for post emergence herbicides
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ID and record weed species
Unit 9: Basic Weed Scouting
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Determine severity of weed infestation
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Count number of weeds/10’ of row for heavy
infestations, weeds/100’ of row for light infestations
Sample area <5 ac
Record weed height & growth stage
Also note soil conditions
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Can help indicate herbicide effectiveness
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Too dry, not enough moisture for chemical uptake
Too wet, herbicide may have leached through root zone
Unit 9: Basic Weed Scouting
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Identify weeds as early as possible for most
effective control
Weed mapping
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Complete a detailed weed map of each field by
mid-May
Will help you monitor changes in weed population
throughout the year, & from year to year
Include:
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Perennial weed locations
Unit 9: Basic Weed Scouting
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Annual weed locations & infestation levels
Mark distinguishing features
Final weed survey
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Timing: late July to mid-August
Add to, or complete another weed map
Don’t generalize observations from areas near
waterways, poorly drained areas, next to borders
Rank species from most commonly to least
commonly found
Unit 9: Basic Weed Scouting
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Economic Threshold guidelines
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Weeds and crop compete for the same resources:
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Soil
Fertility
Sunlight
Water
Problems other than yield losses:
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Clogging, damaging harvest equipment
Loss of cash rented ground to “neater” farmers
Unit 9: Basic Weed Scouting
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Weed infestations the first 4-6 wks, then
treatment = no economic losses
No weeds first 4-6 wks, then weed infestation =
minimal yield losses, but increased weed seed
production
Similar weeds typically cause economic losses in
similar crops
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Grass weeds to grass type crops
Corn weeds to corn type crops
Broadleaf weeds to broadleaf type crops (soybeans)
Unit 9: Basic Weed Scouting
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Giant Foxtail
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Blade is densely hairy
Ligule has fringe hairs
Found through the Midwest
Giant Foxtail
Unit 9: Basic Weed Scouting
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Yellow foxtail
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Sheath is flattened, smooth with split,
overlapping, smooth margins
Blade is smooth with long hairs
Ligule has fringe hairs
Yellow Foxtail
Unit 9: Basic Weed Scouting
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Green Foxtail
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Sheath – round to slightly flat w/ split, overlapping
hairy margins
Blade is smooth to rough w/ rough margins
Ligule is a fringe of hairs
Continuous hairy collar
Green Foxtail
Unit 9: Basic Weed Scouting
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Fall Panicum
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Sheath – slightly flat, smooth w/ split, overlapping
membranous margins
Blade is smooth w/ prominent mid-vein
Ligule is a fringe of hairs
Continuous collar
Fall Panicum
Unit 9: Basic Weed Scouting
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Shattercane
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Sheath – rounded and smooth w/ split,
overlapping thin, membranous margin
Blade – flat w/ sparsely placed hairs on upper
surface
Ligule – long, membranous, rounded w/ jagged
ciliated margin
Shattercane
Unit 9: Basic Weed Scouting
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Johnsongrass
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Very similar to shattercane
Johnsongrass
Unit 9: Basic Weed Scouting
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Yellow Nutsedge
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Leaves – triangular, taper to a point, greenish
yellow
Very distinctive
Yellow Nutsedge
Unit 9: Basic Weed Scouting
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Quackgrass
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Sheath – rounded w/ sparse, short hairs, can be
smooth & split, overlapping margins
Blade – flat, rough to smooth
Ligule – short, membranous, truncate in shape
Quackgrass
Unit 9: Basic Weed Scouting
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Burcucumber
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Hypcotyl – green & rough
Cotyledons – oblong to spoon shaped
True leaves – alternate, pentagon shaped
somewhat hairy
Petioles – long & greed
Fruit – barbed, prickly bristles
Burcucumber
Unit 9: Basic Weed Scouting
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Common Cocklebur
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Hypcotyl – smooth, fleshy, purple tinge near soil
Cotyledons – fleshy, shiny, long and thin shaped
True leaves – opposite (first pair), alternate later
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Serrated leaves
Oval in shape
Rough to hairy surface
Petioles – long, hairy, can be purple spotted
Common Cocklebur
Unit 9: Basic Weed Scouting
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Jimsonweed
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Hypcotyl – fleshy, purple tinged, smooth
Cotyledons – smooth, narrow, short petioles
True leaves – alternate, large, smooth, pointed
apex, toothed margins
Petioles – long, pale green to purple, may have
short hairs
Jimsonweed
Unit 9: Basic Weed Scouting
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Common Lambquarters
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Hypcotyl – purple, smooth
Cotyledons – fleshy, long, oval, dull color
True leaves – seem paired at first, become
alternate
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Pale green
Oval shape
Irregular toothed margins
Petioles – long, pale green
Common Lambsquarters
Unit 9: Basic Weed Scouting
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Ivyleaf Morningglory
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Hypcotyl – dull green to purple, crease along both
sides
Cotyledons – shiny, smooth, deeply indented
base
True leaves – alternate, hairy, three lobed leaves
Petioles – long, hairy, green to reddish tint
Ivyleaf Morningglory
Unit 9: Basic Weed Scouting
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Pitted Morningglory
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Hypcotyl – smooth, somewhat purple
Cotyledons – smooth, butterfly shaped, deeply
indented lobes, pointed
True leaves – alternate, smooth, heart shaped,
maybe purple margins
Petioles – long and pale green to purple
Pitted Morningglory
Unit 9: Basic Weed Scouting
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Tall Morningglory
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Hypcotyl – dull green to purple, smooth
Cotyledons – shiny, smooth, deeply indented
base
True leaves – alternate, hairy broadly heart
shaped, pointed apex
Petioles – long, hairy, dull green to reddish tint
Tall Morningglory
Unit 9: Basic Weed Scouting
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Eastern Black Nightshade
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Hypcotyl – reddish to purple
Cotyledons – pointed tip w/ sparse hairs
True leaves – alternate, oval, wavy tooth margins
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Underside – red to purple
Petioles – red, purple, green, sparse hairs
Eastern Black Nightshade
Unit 9: Basic Weed Scouting
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Smooth Pigweed
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Hypcotyl – reddish purple
Cotyledons – oblong, purple tinge, rough to
smooth
True leaves – alternate, oval, notched or pointed
apex, pale green to reddish
Petioles – long, may be hairy
Root – long, red taproot
Smooth Pigweed
Unit 9: Basic Weed Scouting
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Common Ragweed
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Hypcotyl – purplish, rigid, rough
Cotyledons – club-shaped, rounded apex, smooth
surface
True leaves – opposite, irregular lobed
Petioles – grooved, widen to V-shaped stem
Common Ragweed
Unit 9: Basic Weed Scouting
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Giant Ragweed
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Hypcotyl – smooth, shiny, can be purple blotched
Cotyledons – spatulate, rounded apex gradually
narrowing to base, smooth, shiny
True leaves – opposite, oval, pointed w/ serrated
margins, rough short-haired surface
Petioles – concave above, winged toward stem,
rough hairy surface
Giant Ragweed
Unit 9: Basic Weed Scouting
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Smartweed
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Hypcotyl – smooth, tinged dark purple
Cotyledons – smooth, fleshy, elongated, shiny w/
hairy margins
True leaves – alternate and elongated, shiny, may
be spotted purple, hairy margins
Petioles – short, arise from swollen joints
Smartweed
Unit 9: Basic Weed Scouting
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Waterhemp
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Hypcotyl – reddish purple
Cotyledons – oblong, purple tinge
True leaves – alternate, narrow oval to elongated,
pale greed to reddish, smooth
Petioles - long
Waterhemp
Unit 9: Basic Weed Scouting
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Velvetleaf
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Hypcotyl – velvety, soft short hairs
Cotyledons – heart shaped, rounded apex, fuzzy
surface
True leaves – alternate, heart shaped, rounded
apex, serrated margin, velvety surface
Petioles – round, covered w/ soft hairs
Velvetleaf
Unit 9: Basic Weed Scouting
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Field Bindweed (perennial)
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Hypcotyl – smooth
Cotyledons – kidney shaped
True leaves – alternate, spade shaped, smooth
Petioles - smooth
Field Bindweed
Unit 9: Basic Weed Scouting
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Hedge Bindweed (perennial)
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Hypcotyl – smooth
Cotyledons – kidney shaped
True leaves – alternate, larger than field
bindweed, arrowhead shaped
Petioles - smooth
Hedge Bindweed
Unit 9: Basic Weed Scouting
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Hemp Dogbane (perennial)
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Hypcotyl – red above ground
Cotyledons – elongated, smooth
True leaves – opposite, elliptic, thick, shiny, white
midvein
Petioles – short, smooth, “milklike” sap
Hemp Dogbane
Unit 9: Basic Weed Scouting
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Common Milkweed (perennial)
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Hypcotyl – pale green to purple
Cotyledons – elliptical, thick, covered w/ short
hairs
True leaves – opposite, thick, dull, velvety,
elliptical, pointed
Petioles – ridged, “milklike” sap
Common Milkweed
Unit 9: Basic Weed Scouting
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Honeyvine Milkweed (perennial)
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Hypcotyl – green to slightly pink, smooth
Cotyledons – shiny, oblong, rounded apex,
narrows into long petiole
True leaves – opposite, oblong to heart shaped,
pointed apex, dull green to bluish tint
Petioles – long, sparsely hair covered
Honeyvine Milkweed