Unit 9: Basic Weed Scouting

Unit 9: Basic Weed Scouting Unit 9 Objectives: Knowledge of basic scouting procedures Understanding of proper scouting times Using field weed surveys Basic weed ID

Unit 9: Basic Weed Scouting Early season weed scouting Done within 2 wks of planting after emergence Also can determine: Need for hoeing Preemergence & preplant herbicides Need for post emergence herbicides ID and record weed species

Unit 9: Basic Weed Scouting Determine severity of weed infestation 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 Can help indicate herbicide effectiveness Too dry, not enough moisture for chemical uptake Too wet, herbicide may have leached through root zone

Unit 9: Basic Weed Scouting Identify weeds as early as possible for most effective control Weed mapping 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: Perennial weed locations

Unit 9: Basic Weed Scouting Annual weed locations & infestation levels Mark distinguishing features Final weed survey 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 Economic Threshold guidelines Weeds and crop compete for the same resources: Soil Fertility Sunlight Water Problems other than yield losses: Clogging, damaging harvest equipment Loss of cash rented ground to “neater” farmers

Unit 9: Basic Weed Scouting 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 Grass weeds to grass type crops Corn weeds to corn type crops Broadleaf weeds to broadleaf type crops (soybeans)

Unit 9: Basic Weed Scouting Giant Foxtail Blade is densely hairy Ligule has fringe hairs Found through the Midwest

Giant Foxtail

Unit 9: Basic Weed Scouting Yellow foxtail 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 Green Foxtail 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 Fall Panicum 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 Shattercane 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 Johnsongrass Very similar to shattercane

Johnsongrass

Unit 9: Basic Weed Scouting Yellow Nutsedge Leaves – triangular, taper to a point, greenish yellow Very distinctive

Yellow Nutsedge

Unit 9: Basic Weed Scouting Quackgrass 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 Burcucumber 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 Common Cocklebur Hypcotyl – smooth, fleshy, purple tinge near soil Cotyledons – fleshy, shiny, long and thin shaped True leaves – opposite (first pair), alternate later Serrated leaves Oval in shape Rough to hairy surface Petioles – long, hairy, can be purple spotted

Common Cocklebur

Unit 9: Basic Weed Scouting Jimsonweed 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 Common Lambquarters Hypcotyl – purple, smooth Cotyledons – fleshy, long, oval, dull color True leaves – seem paired at first, become alternate Pale green Oval shape Irregular toothed margins Petioles – long, pale green

Common Lambsquarters

Unit 9: Basic Weed Scouting Ivyleaf Morningglory 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 Pitted Morningglory 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 Tall Morningglory 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 Eastern Black Nightshade Hypcotyl – reddish to purple Cotyledons – pointed tip w/ sparse hairs True leaves – alternate, oval, wavy tooth margins Underside – red to purple Petioles – red, purple, green, sparse hairs

Eastern Black Nightshade

Unit 9: Basic Weed Scouting Smooth Pigweed 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 Common Ragweed 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 Giant Ragweed 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 Smartweed 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 Waterhemp 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 Velvetleaf 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 Field Bindweed (perennial) Hypcotyl – smooth Cotyledons – kidney shaped True leaves – alternate, spade shaped, smooth Petioles - smooth

Field Bindweed

Unit 9: Basic Weed Scouting Hedge Bindweed (perennial) Hypcotyl – smooth Cotyledons – kidney shaped True leaves – alternate, larger than field bindweed, arrowhead shaped Petioles - smooth

Hedge Bindweed

Unit 9: Basic Weed Scouting Hemp Dogbane (perennial) 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 Common Milkweed (perennial) 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 Honeyvine Milkweed (perennial) 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