A Parliamentary Owl Consulting project
Weed Identification
Barnyardgrass
Coarse summer annual grass reaching 1–5 ft. The absence of a ligule is the single most reliable identification feature.
- NO ligule — smooth bare collar region
- Flattened keeled stem, often red-purple at base
- Purplish-brown finger-like racemes with awned spikelets
- Common in wet, disturbed areas and irrigated crop fields
Black Nightshade
Upright broadleaf 1–2 ft. Small white star-shaped flowers; round berries green then turning black at maturity. Foul odor when crushed.
- White 5-petaled star flowers with yellow anther cone
- Round berries: green → black at maturity
- Irregular sinuate leaf margins
- Foul odor when foliage is crushed
Buckhorn Plantain
Rosette-forming perennial with narrow lance-shaped leaves bearing 3–5 prominent parallel ribs. Cylindrical spike on long ridged stalk.
- NARROW lance-shaped leaves — contrast with broadleaf plantain's oval leaves
- 3–5 prominent parallel ribs running leaf length
- Cylindrical spike flower head with visible white stamens
- Fibrous roots; sessile leaves (no petiole)
Canada / Bull / Sow Thistle
Spiny-leaved thistles. Canada thistle is a creeping perennial with extensive root system — a Nebraska Prohibited Noxious Weed.
- Canada: smaller flowerheads, no stem wings, creeping perennial roots — NE Prohibited
- Bull: large solitary head, spiny-winged stem, biennial
- Sow: milky sap when broken, hollow stem, annual
- All: alternate spiny leaves, composite purple flower heads
Downy Brome / Cheat
Soft, densely hairy winter annual grass — one of the most troublesome weeds in Nebraska winter wheat.
- SOFT DENSE HAIRS covering entire plant: leaves, sheath, seed head
- Drooping, nodding panicle with long awns
- Membranous ligule; no auricles
- Purplish-red seed head at maturity, drooping to one side
Common Cocklebur
Coarse summer annual 1–4 ft. Toxic as a cotyledon-stage seedling. Produces spiny burs that attach to clothing and animals.
- SPINY EGG-SHAPED BUR with 2 hooked terminal spines — unmistakable
- Sandpaper-rough texture on both leaf surfaces
- Stem often spotted/mottled purple
- Cotyledon stage highly toxic to livestock
Common Lambsquarters
Upright summer annual 2–5 ft. The white/gray mealy coating on young leaves and growing tips is the hallmark feature.
- WHITE/GRAY MEALY COATING on young leaves — like powdered sugar
- Diamond- to triangular-shaped leaves with irregular toothed margins
- Tiny green flowers in terminal spikes
- Smooth stem with green/red stripes
Common Mallow
Low-growing spreading annual or biennial. Round kidney-shaped leaves with 5–7 shallow lobes. Distinctive round segmented seed capsule.
- Rounded shallowly lobed leaves with crinkled margins
- Small whitish-pink flowers with notched petals
- ROUND SEGMENTED SEED CAPSULE — looks like a wheel of cheese ('cheeseweed')
- Prostrate to spreading growth habit
Common Milkweed
Robust perennial 2–5 ft with thick opposite leaves and milky latex sap in all plant parts. Large bumpy seed pods split to release silky seeds.
- MILKY WHITE LATEX SAP when any plant part is broken — most reliable feature
- Large thick opposite leaves (4–8 in); fine white hairs on underside
- Large warty/bumpy seed pod splitting to release seeds with silky hairs
- Complex flower with 5 reflexed petals and corona; pink-purple globe clusters
Common / Giant Ragweed
Major allergen weed. Common ragweed has deeply fern-like lobed leaves. Giant ragweed has large opposite 3-lobed leaves and reaches 6–12 ft.
- Common: deeply pinnately lobed fern-like leaves; soft-hairy stem
- Giant: large OPPOSITE leaves with 3 palmate lobes; very tall and coarse
- Both: small greenish flowers in terminal racemes; hairy stems
- Both: burr-like seed with projections
Common Sunflower
Large coarse summer annual 3–8 ft. Rough sandpaper-like hairy leaves. Wild type has multiple smaller heads vs. single large head in crop type.
- ROUGH BRISTLY HAIRS covering leaves and stems — sandpaper texture
- Heart-shaped lower leaves; alternate leaves on upper stem
- Wild: branched with multiple smaller heads (vs. single crop head)
- Seeds: small black/striped achenes
Large Crabgrass
Low-growing summer annual grass that roots at stem nodes. Forms dense spreading mats in row crop fields.
- Sprawling branching stems that ROOT AT LOWER NODES
- Leaf blade densely hairy on upper surface and margin
- Membranous ligule; no auricles
- Seed head: 3–12 finger-like racemes radiating from stem tip
Curly Dock
Upright perennial 2–4 ft with large lance-shaped leaves with distinctively curled margins. Deep taproot. Rust-brown papery seed clusters in fall.
- STRONGLY CURLED/WAVY LEAF MARGINS — most reliable feature
- Large basal rosette of long lance-shaped leaves
- Rust-brown 3-winged seed clusters on tall stalks in fall
- Deep fleshy taproot; yellow interior when cut
Dandelion
Familiar rosette-forming perennial. Deeply toothed basal leaves; hollow scape bearing single yellow head; white spherical puffball seed head.
- MILKY WHITE LATEX SAP in all plant parts
- Leaves: deeply pinnately lobed with teeth pointing backward toward base
- HOLLOW leafless flower stalk (scape); single yellow composite head
- White spherical 'clock' puffball seed head
Field Bindweed
Persistent creeping perennial vine with deep extensive root system. Arrow-shaped leaves; pink or white funnel-shaped flowers.
- ARROW/SPEAR-SHAPED LEAVES with basal lobes pointing outward
- Pink or white funnel/trumpet flowers (1 in); 2 small bracts well below calyx
- Vining twining growth habit; wraps around crop stems
- Deep white fleshy roots extending 20+ ft; NE Prohibited Noxious Weed
Foxtail (Yellow / Green / Giant)
Three closely related summer annual grasses with bristly cylindrical seed heads. Most common weeds in Nebraska row crops.
- Yellow foxtail: TWISTED HAIR TUFTS at collar; yellow-orange bristles; compressed sheath
- Green foxtail: no twisted hairs; green or purple bristles; most common in Nebraska
- Giant foxtail: largest (to 6 ft); NODDING seed head; hairy upper leaf surface
- All three: cylindrical bristle-covered seed head; ligule is a fringe of hairs
Ground Cherry
Related to nightshade and tomato. The papery lantern-shaped husk enclosing the small berry fruit is the unmistakable identification feature.
- PAPERY LANTERN-LIKE HUSK enclosing a small tomato-like fruit — unmistakable
- Yellow bell-shaped flowers with dark purple center spots
- Alternate ovate leaves with wavy or coarsely toothed margins
- Sticky-hairy stem in some species
Horse Nettle
Spiny perennial in the nightshade family. Both leaf surfaces and stem bear sharp yellow spines. White to lavender star flowers.
- SHARP STRAW-COLORED SPINES on stem and leaf midribs — wear gloves
- White to lavender star-shaped flowers with yellow anther cone
- Round berries: yellow-orange when ripe; toxic to humans and livestock
- Deeply lobed leaves with star-shaped hairs visible with hand lens
Jimsonweed
Extremely toxic — all parts especially seeds contain tropane alkaloids. Large white trumpet flowers and spiny seed capsule are unmistakable.
- LARGE WHITE TRUMPET-SHAPED FLOWER (3–4 in long) opening in evening
- SPINY EGG-SHAPED SEED CAPSULE — distinctive and unmistakable
- Large coarsely toothed rank-smelling leaves
- Smooth often purple-tinged thick stem; ALL PARTS HIGHLY TOXIC
Johnsongrass
Tall robust perennial grass 3–6 ft spreading by seeds AND rhizomes. Nebraska Prohibited Noxious Weed. Prominent white midrib in leaf blade.
- PROMINENT WHITE MIDRIB running length of broad leaf blade
- Hairy fringed membranous ligule
- Large open branching purple-tinged panicle seed head
- Scaly RHIZOMES (underground stems) with finger-like nodes; NE Prohibited
Morning Glory (Tall / Ivyleaf)
Twining summer annual vine. Funnel-shaped flowers in purple, pink, or blue. Wraps around crop stems causing harvest problems.
- Tall: HEART-SHAPED unlobed leaves; large purple to pink funnel flowers
- Ivyleaf: DEEPLY 3-LOBED ivy-like leaves; smaller blue to pale purple flowers
- Both twine clockwise on crop stems; hairy stems
- Distinct from field bindweed by hairy stems and heart/lobed (not arrow) leaves
Yellow Nutsedge
Grass-like perennial SEDGE spreading by underground tubers (nutlets). 'Sedges have edges' — triangular stem cross-section distinguishes from grasses.
- TRIANGULAR STEM — 'sedges have edges' (grasses round, rushes round)
- Leaves in groups of 3 (vs. 2 ranks in grasses)
- Yellow-brown spikelets in umbrella-like clusters
- Small brown NUTLETS (tubers) at root tips spread the plant
Puncturevine
Prostrate summer annual. Produces extremely sharp hard burs ('goat-heads') that puncture bicycle tires and injure animal feet.
- WOODY BUR WITH 2–4 SHARP HARD SPINES — punctures tires and skin
- Mat-forming prostrate growth habit; dense hairy stems
- Opposite pinnately compound leaves with small oblong leaflets
- Small (1/2 in) yellow 5-petaled flowers
Redroot Pigweed
Coarse upright summer annual 2–5 ft. Pink-red taproot is the most reliable identification feature. Dense bristly seed head.
- PINK-RED TAPROOT AND LOWER STEM — most reliable feature
- Hairy stem and leaf undersides (unlike waterhemp which is smooth)
- Short dense bristly terminal seed head; bracts longer than sepals
- Ovate-to-rhombic leaf with notched tip and wavy margin
Russian Thistle / Tumbleweed
The iconic tumbleweed. Dense bushy summer annual that breaks off at soil line and tumbles in wind. Abundant in dryland western Nebraska.
- Young: soft cylindrical needle-like fleshy green leaves
- Mature: hard spiny plant with striated red-green stems and bushy rounded form
- BREAKS OFF at soil line and tumbles in wind dispersing seeds
- Abundant in dryland fields and roadsides in western Nebraska
Shepherd's Purse
Small winter annual 4–16 in. Deeply lobed basal rosette. Triangular heart-shaped seed pods resemble an old-fashioned coin purse.
- TRIANGULAR NOTCHED (HEART-SHAPED) SEED PODS — unmistakable
- Deeply pinnately lobed basal leaves; stem leaves clasp the stem
- Small white 4-petaled cross-shaped flowers (Brassicaceae pattern)
- Common in wheat fields and disturbed areas
Pennsylvania Smartweed
Upright summer annual with lance-shaped leaves. Swollen papery sheath (ocrea) at each node is the Polygonaceae family ID feature.
- SWOLLEN PAPERY SHEATH (OCREA) at each stem node — characteristic of Polygonaceae
- Pink to rose dense terminal spike flower heads
- Leaves lance-shaped; may have dark chevron marking
- Commonly found in wet low areas and irrigated fields
Wild Mustard
Annual mustard with bright yellow 4-petaled cross-shaped flowers and hairy stems. Important winter wheat broadleaf weed.
- BRIGHT YELLOW CROSS-SHAPED (CRUCIFORM) FLOWERS — 4 petals
- Lower leaves coarsely lobed lyre-shaped; upper leaves clasp the stem
- HAIRY STEM (vs. smooth waxy stem of crop canola)
- Cylindrical seed pod with long beak; ribbed surface
Wild Oats
Winter annual grass resembling cultivated oats. Distinctive large drooping panicle with large spikelets bearing twisted bent awns.
- LARGE DROOPING OPEN PANICLE with horseshoe-shaped spikelets
- TWISTED BENT (GENICULATE) AWN — looks like a bent pin; hygroscopic
- Membranous jagged-edged (erose) ligule; no auricles
- Clockwise-twisted floret base
Silverleaf Nightshade
Perennial nightshade with silvery star-shaped hairs giving leaves a gray-silver appearance. Prickly stem and midribs; purple flowers.
- SILVERY-GRAY LEAF COLOR from dense star-shaped hairs — most reliable feature
- Spine-tipped prickles on stems and midribs
- Violet/purple star-shaped flowers with yellow anther cone
- Round berries: green mottled pattern → yellow-orange when ripe
Broadleaf Plantain
Low rosette perennial with broad oval strongly ribbed leaves. Distinguished from buckhorn plantain by wide egg-shaped vs. narrow lance-shaped leaves.
- BROAD OVAL EGG-SHAPED LEAVES (vs. narrow in buckhorn plantain)
- 5–9 prominent parallel ribs; well-defined petiole
- Cylindrical narrow spike with tiny greenish flowers
- Fibrous root system; rosette growth form
Crop Plant & Seed Identification
Alfalfa
Premier forage legume of Nebraska. Trifoliolate leaves finely serrated near tip. Purple flowers. Small kidney-shaped seeds.
- Trifoliolate leaves with leaflets finely serrated near tip
- Purple (or yellow in some varieties) flower clusters
- SMALL KIDNEY-SHAPED SEEDS — yellow to olive-green, smooth
- Nitrogen-fixing root nodules with Bradyrhizobium bacteria
Barley
Small grain with distinctive long clasping hairy auricles at the leaf collar. 6-row (most common in NE) or 2-row types. Long awns on seed head.
- LARGE CLAW-LIKE HAIRY AURICLES at collar — most reliable small grain feature
- 3 spikelets per node in head (vs. 1 in wheat)
- Seed: enclosed in hull, elongated, pale gold
- Longest awns of the small grains
Canola
Important oilseed crop. Very small round dark brown seeds. Waxy blue-green leaves; bright yellow 4-petaled cross flowers.
- TINY ROUND SEEDS (like small BBs) — dark reddish-brown to black
- Smooth waxy blue-green stems (vs. hairy wild mustard)
- Bright yellow cross-shaped 4-petaled flowers
- Seeds much smaller than mustard; rounder than radish
Corn — Dent
Nebraska's primary grain crop. Large flat seed with a dent in the crown at maturity. Yellow most common. Embryo visible on flat face.
- DENT IN CROWN of seed from soft starch shrinkage at maturity
- Flat on embryo side; rounded back; much larger than other cereal grains
- Yellow (dent corn) or white; germ visible as lighter area on face
- Plant: large midrib in leaf; no auricles; distinct from sorghum
Oats
Spring small grain with open drooping panicle (unlike spike of wheat/barley). Hulled grain, elongated and golden.
- OPEN SPREADING PANICLE (not a spike) — key contrast to wheat/barley/rye
- Elongated narrow seed enclosed in hull
- NO AURICLES; large membranous ligule
- No awn or very short awn (vs. long twisted awn in wild oats)
Grain Sorghum (Milo)
Drought-tolerant summer annual. Round small tan to reddish-brown seeds. Compact erect seed head. White midrib in leaf blade.
- COMPACT UPRIGHT PANICLE (vs. open drooping in Johnsongrass)
- Round seeds ~4mm; tan to reddish-brown
- WHITE MIDRIB in leaf blade; hairy nodes on stem
- Shorter plant (3–5 ft) than Johnsongrass; NO rhizomes
Soybean
Round to oval pale yellow seeds with tan-buff hilum. Trifoliolate hairy leaves and pods. Stipules at leaf base.
- Round to oval pale yellow seed; OVAL TAN HILUM (seed scar)
- Smooth shiny seed coat; much larger/rounder than alfalfa or clover
- Trifoliolate leaves with stipules at base; hairy stems and pods
- Nitrogen-fixing nodules with Bradyrhizobium japonicum
Sugarbeet
Key Panhandle crop. Large conical white taproot. Broad wavy glossy dark green leaves on long petioles. Corky multigerm seed cluster.
- Seed = MULTIGERM CLUSTER (corky irregular reddish-brown) or monogerm (single rounded)
- Plant: large glossy wavy-margined basal leaves with long petioles
- Large WHITE CONICAL STORAGE ROOT with high sucrose content
- Biennial — requires vernalization to flower
Sunflower (Crop)
Cultivated sunflower for oilseed or confection. SINGLE large terminal head on single erect stem. Seeds larger than wild type.
- SINGLE LARGE HEAD on erect stem (vs. branched multiple heads in wild type)
- Oilseed: black seeds; Confection: striped larger seeds
- Rough hairy leaves and stems (same as wild, but plant is taller and unbranched)
- Achenes much larger and more uniform than wild common sunflower
Red Clover
Important forage legume. Trifoliolate leaves with V-shaped pale marking on each leaflet. Purple-red globe flower heads.
- V-SHAPED PALE CHEVRON marking on each leaflet
- Small heart- to egg-shaped seeds — yellow to violet, about 2mm
- Round red/purple GLOBOSE flower head (no stalk on individual flowers)
- Hairy leaves and stem; larger seed than alfalfa
White Clover
Low-growing perennial legume spreading by stolons. White globe flower heads. Trifoliolate leaves often with white chevron marking.
- WHITE GLOBE FLOWER HEADS on leafless peduncles
- Spreading by stolons (aboveground runners) — forms dense sod
- Trifoliolate leaves often with white crescent or chevron marking
- Very small seeds — similar to red clover but rounder and lighter
Insect Identification
Alfalfa Weevil
Major alfalfa pest. Adults: small brown snout beetle with darker dorsal stripe. Larvae: bright green legless grubs with white stripe and black head.
- Adult: 3/16 in brown weevil with DOWNWARD-CURVED SNOUT; darker brown dorsal stripe
- Larva: GREEN LEGLESS C-curved; distinct BLACK HEAD; white dorsal stripe
- Damage: skeletonized alfalfa tips appear SILVERY-GRAY from distance
- ET: 1–2 larvae per stem (3rd instar)
Aphids — Soybean Aphid
Tiny soft-bodied insects forming colonies on new growth. Produce sticky honeydew. Soybean aphid: yellow-green with black cornicles.
- Tiny (1–2 mm) pear-shaped soft body; various colors by species
- CORNICLES (TAILPIPES) — small tubes projecting from rear of abdomen
- Winged and wingless forms in same colony
- Soybean aphid: YELLOW-GREEN body; BLACK CORNICLES; on soybean terminals
Assassin Bug
Important predator of crop pest insects. Elongated body; curved dagger-like beak held under the head. Actively stalks and impales prey.
- CURVED HEAVY BEAK held under the head when not feeding — most reliable feature
- NARROW 'NECK' connecting head to body
- Long grasping forelegs used to hold prey
- Can deliver painful bite if handled carelessly
Field Cricket
Large black cricket with long antennae, enlarged hind jumping legs, and long ovipositor on females. Minor crop pest.
- JET BLACK or dark brown; large (1 inch); flattened body
- VERY LONG FILAMENTOUS ANTENNAE — longer than body
- ENLARGED HIND FEMORA for jumping
- Female: LONG NEEDLE-LIKE OVIPOSITOR between 2 cerci (tails)
Chinch Bug
Tiny slow-moving bug sucking sap from stems at soil line in large colonies. Adults: black with white wings. Red nymphs with white stripe.
- Adult: 1/6 in; BLACK BODY, WHITE WINGS with black triangular spot
- Nymph: BRIGHT RED-ORANGE with white band across abdomen
- Characteristic foul smell when crushed
- Aggregates at base of plant stems; dryland fields
Corn Earworm
Major pest entering corn ear through silk. Larva HIGHLY VARIABLE in color with alternating stripes; rough microspines on body surface.
- VARIABLE COLOR larva (green, tan, brown, pink) with alternating light and dark stripes
- MICROSPINES on body surface visible under hand lens — consistent feature
- Enters corn at silk end; feeds down into ear tip
- Adult moth: tan-yellow with gray-brown markings
Cutworms
Fat smooth caterpillars found at or below soil surface. Cut corn seedlings at soil line. Black cutworm: dull gray-black with small bumpy tubercles.
- Fat smooth GREASY-LOOKING caterpillar; CURLS INTO TIGHT C when disturbed
- Black cutworm: dark granular skin; cuts stems AT OR BELOW SOIL SURFACE
- Found at base of cut plants when soil is excavated
- Scout corn V1–V5 for fresh cut plants in early morning
European Corn Borer
Pale tan caterpillar with small brown-gray CIRCULAR SPOTS (tubercles) on each segment. Bores into corn stalk causing lodging.
- Pale tan to pinkish-cream with ROWS OF SMALL DARK BROWN CIRCULAR SPOTS
- Dark head capsule; about 1 inch at maturity
- SHOT-HOLE FEEDING on leaves before boring into stalk
- Corn stalk breakage at ear zone; sawdust-like frass at entry holes
Grasshopper
Familiar crop and rangeland pest. Large hind legs for jumping. Differential grasshopper has distinct herringbone black pattern on inner hind femur.
- Enlarged muscular HIND LEGS for jumping
- Differential: HERRINGBONE BLACK MARKINGS on inner hind femur — most reliable feature
- Redlegged: RED COLORING on hind tibia
- Incomplete metamorphosis — nymphs look like small adults
Green Lacewing
Important predator of aphids and mites. Adults: bright green, large iridescent net-veined wings, golden eyes. Larvae are voracious 'aphid lions'.
- Bright green delicate body; IRIDESCENT GOLDEN EYES — unmistakable
- Large intricately NET-VEINED transparent green wings held tent-like over body
- Larvae: alligator-shaped mottled gray-brown with long curved mandibles
- Eggs on SLENDER STALKS attached to plant surfaces
Ladybird Beetle (Lady Beetle)
Among the most important beneficial insects in crop fields. Round dome-shaped orange-red with 7 black spots. Larvae also voracious aphid predators.
- Round STRONGLY DOMED; ORANGE-RED WITH 7 BLACK SPOTS (7-spot species)
- Short clubbed antennae; 6 short legs visible beneath
- Larva: flat elongated; BLACK WITH ORANGE LATERAL SPOTS (alligator-shaped)
- Both adult and larva consume aphids, mites, and scale insects
Leafhopper
Small wedge-shaped pale green insects. RUNS SIDEWAYS when disturbed. Causes 'hopperburn' — V-shaped yellowing at leaf tips.
- Small (1/8 in); WEDGE-SHAPED body tapering to rear; pale green
- RUNS SIDEWAYS when disturbed — most distinctive behavior
- Causes V-SHAPED TIP YELLOWING (hopperburn) from phloem feeding
- Rows of spines on hind tibia; wings held tent-like
Colorado Potato Beetle
Major defoliator of potato/tomato/pepper. BOLD YELLOW/ORANGE AND BLACK STRIPED ELYTRA pattern is unmistakable. History of insecticide resistance.
- YELLOW/ORANGE BODY WITH 10 BLACK STRIPES ON ELYTRA — unmistakable
- Yellow-orange BRICK-SHAPED EGGS in neat clusters on leaf undersides
- Larva: FAT RED-ORANGE with two rows of black spots on sides
- Has developed resistance to virtually every insecticide class
Two-Spotted Spider Mite
NOT a true insect — 8 legs, 2 body segments, Arachnida. Tiny yellow-green mites on leaf undersides. Fine webbing on infested leaves.
- Tiny (0.5mm) oval; 8-LEGGED ARACHNID — not a 6-legged insect
- TWO DARK SPOTS on each side of greenish-yellow abdomen
- Fine silken WEBBING on undersides of infested leaves
- STIPPLING damage: tiny pale dots on upper leaf surface
Green Stink Bug
Shield-shaped bright green bug with orange-red and black band on abdomen edge. Produces defensive stink. Piercing-sucking feeder.
- SHIELD-SHAPED BODY; BRIGHT GREEN with orange/red and black margin markings
- 3-segmented beak held under body; sucking mouthparts
- Produces FOUL-SMELLING CHEMICAL when disturbed
- BARREL-SHAPED EGGS in neat rows on leaf surfaces
Wireworm
Larvae of click beetles. Narrow cylindrical hard shiny yellowish-brown grubs. Feed on germinating seeds and roots. Live in soil 3–5 years.
- HARD SLENDER WIRE-LIKE BODY; shiny jointed; yellowish-brown
- DOES NOT CURL (unlike fat C-curved white grubs)
- Three pairs of small true legs near head; very hard cuticle
- Adult (click beetle): can flip upright with CLICKING SOUND
White Grub
FAT C-CURVED white grubs that feed on corn roots. Much fatter and softer than wireworm. Identified by raster pattern at posterior end.
- FAT C-CURVED WHITE GRUB; brown head capsule; 3 pairs of legs near head
- MUCH FATTER than wireworm; soft not hard
- RASTER PATTERN: unique parallel rows of spines on last abdominal segment
- Adult: large oval brown May beetle (June bug) attracted to lights
Diseases, Nutrients & Disorders
Gray Leaf Spot — Corn
Most economically important foliar disease of Nebraska corn. RECTANGULAR lesions bounded by leaf veins — the single most reliable ID feature.
- RECTANGULAR LESIONS bounded by leaf veins — most reliable vs. NCLB
- Tan to grayish color; no concentric rings; no distinct margin
- Progresses from LOWER LEAVES upward
- Favored by warm humid nights and high crop residue
Northern Corn Leaf Blight
Large CIGAR-SHAPED lesions on corn leaves — contrast to GLS rectangular lesions. Grayish-green to tan; 1–6 inches long.
- CIGAR-SHAPED (boat-shaped) lesions 1–6 inches long — most distinctive feature
- NOT bounded by veins (contrast to GLS rectangular, vein-bounded lesions)
- Dark sporulation on lesion in humid weather
- Progresses from lower to upper leaves
Sudden Death Syndrome — Soybean
Foliar symptoms caused by toxins from root infection, NOT direct leaf infection. Interveinal chlorosis with green veins retained.
- INTERVEINAL CHLOROSIS/NECROSIS WITH GREEN VEINS RETAINED
- Leaflets drop but PETIOLES REMAIN attached to stem
- Root cortex: gray-brown rot; blue-tinged fungal growth on roots
- Internal stem PITH REMAINS WHITE (contrast: brown stem rot = brown pith)
Soybean Cyst Nematode (SCN)
Most yield-limiting pathogen of soybean in Nebraska. Tiny white or lemon-yellow PINHEAD-SIZED CYSTS visible on roots at R3–R6 stage.
- TINY WHITE/LEMON-YELLOW PINHEAD CYSTS on roots at R3–R6
- Cysts DO NOT wash off roots easily (unlike nitrogen-fixing nodules)
- NODULES are larger and differently attached than pinhead cysts
- Foliar: yellowing and stunting in IRREGULAR OVAL FIELD PATTERNS
Common Corn Smut
Produces visible dramatic galls on any aboveground plant part. Young galls are white/silver and fleshy; mature galls burst to release black powdery spores.
- LARGE IRREGULAR GALLS (tumor-like) on ears, stalks, leaves, or tassel
- Young galls: FLESHY WHITISH-SILVER, firm
- Mature galls: DARK GRAY-BLACK POWDERY MASS (teliospores)
- Spreads by windborne spores through wound sites — not residue-borne
Nitrogen Deficiency — Corn
V-shape yellowing starting at leaf tip of LOWER OLD LEAVES progressing toward base along midrib. Mobile nutrient — moves from old to new tissue.
- V-SHAPED YELLOWING from leaf tip down midrib on OLDEST LOWER LEAVES
- Begins on lower leaves; progresses UP plant as deficiency worsens
- General pale green color overall before distinct V pattern develops
- MOBILE NUTRIENT — symptoms on OLD tissue (contrast to Fe chlorosis on new)
Iron Deficiency Chlorosis — Soybean
Interveinal chlorosis on YOUNG UPPER LEAVES. Green veins remain visible against yellowed tissue. Caused by high-pH calcareous soils limiting iron availability.
- INTERVEINAL CHLOROSIS ON YOUNG UPPER LEAVES — contrast to N deficiency on old leaves
- GREEN VEINS REMAIN VISIBLE against yellow background
- IMMOBILE NUTRIENT — symptoms appear on YOUNG tissue first
- Associated with CALCAREOUS SOILS with high pH and high bicarbonate
Frogeye Leaf Spot — Soybean
Circular to irregular spots with gray-brown center and distinct REDDISH-PURPLE BORDER — the two-toned 'frog's eye' appearance.
- CIRCULAR LESIONS: GRAY/TAN CENTER WITH DISTINCT REDDISH-PURPLE BORDER — key feature
- Resembles a frog's eye — two-toned appearance is diagnostic
- Light gray sporulation in lesion center under humid conditions
- Fungicide-resistant strains (Group 11 strobilurin) widespread in Nebraska
CDE Study Tips & Exam Strategies
Grass Weed ID — Collar Region Method
Always check the collar region first using a 10x hand lens. Three questions in order:
- Ligule? Membranous, hairy fringe, or absent?
- Auricles? Large and clasping (barley) or absent?
- Blade texture? Hairy or smooth?
This three-step process separates 90% of grass weeds and crops at the CDE. Barnyardgrass has NO ligule — the absence is itself the ID feature.
Life Cycle Quick Reference
- Winter Annuals: Germinate fall → overwinter → seed in spring. Downy brome, shepherd's purse, wild oats, winter wheat, barley, rye.
- Summer Annuals: Germinate spring → die at first frost. Foxtails, pigweed, lambsquarters, cocklebur, ragweed, morning glory, barnyardgrass.
- Biennials: 2-year cycle. Wild carrot, bull thistle, sweetclover, musk thistle, common mallow.
- Perennials: Live 3+ years. Canada thistle, field bindweed, curly dock, Johnsongrass, common milkweed, dandelion.
Small Grain Comparison
- Barley: Large hairy clasping auricles; 3 spikelets/node; longest awns; hulled seed.
- Wheat: Small smooth auricles or absent; 1 spikelet/node; usually awnless; reddish-brown hard seed with crease.
- Rye: Small auricles; narrow blue-green leaves; slender head.
- Oats: NO auricles; open spreading panicle (not spike); rounded membranous ligule; hulled elongated seed.
Nutrient Deficiency — Mobile vs. Immobile
Mobile nutrients → OLD leaves first:
- N: V-shaped yellowing from leaf tip on lower leaves
- P: Purple coloration of leaves and stems
- K: Marginal leaf scorch on oldest leaves
- Mg: Interveinal chlorosis on lower leaves
Immobile nutrients → NEW leaves first:
- Fe: Interveinal chlorosis on young upper leaves (green veins remain)
- Zn: White striping on corn; interveinal bronze on soybean
- S: Uniform yellowing of young leaves
Insect Order Quick Reference
- Coleoptera (Beetles): Hardened elytra; complete metamorphosis. Alfalfa weevil, lady beetle, wireworm, white grub, CPB.
- Lepidoptera (Moths): Scaled wings; complete metamorphosis. Corn earworm, cutworms, European corn borer.
- Hemiptera (True Bugs): Piercing-sucking mouthparts; incomplete metamorphosis. Aphids, stink bugs, chinch bug, leafhopper, assassin bug.
- Orthoptera: Large hind legs; incomplete metamorphosis. Grasshopper, field cricket.
- Acari (Mites): 8 legs — NOT insects. Spider mite.
Nebraska Noxious & Prohibited Weeds
Prohibited (cannot be present in seed; must be controlled):
- Field bindweed, Johnsongrass, Musk thistle, Canada thistle, Leafy spurge, Purple loosestrife
Key CDE tip: Know whether each weed is on the Nebraska noxious/prohibited list — this is often a specific question on the written exam and in the disorder practicum scoring. Field bindweed and Johnsongrass appear most frequently.