Carefully examine plant for damage symptoms and look on, in and around damaged plant for insects possibly responsible for observed damage. Although damage symptoms can be defininitive enough to make reasonable estimates of the causative agent, presence of the pest is usually required to make positive identification.
Which of the following 2 choices BEST describes the damage?
1) General plant damage, poor stand, wilted, lodged, stunted, distorted, discolored plants . . . go to General Plant Damage Key
2) Specific plant parts damaged: seed, root, stalk, leaf, tassel, ear with damage, or presence of insects . . . go to Specific Plant Part Damage Key
Back to Home page
General Plant Damage Key - Carefully examine soil around base of plants, roots, base of stalk for insects and insect damage then select the best description from below:
| 1) Poor stand or germination . . . go to Seed Damage Key | |
| 2) Plants wilted or lodged: | |
| a) Roots severed or damaged . . . go to Root Damage Key | |
| b) Stalk with entry or puncture holes at or near base of plant, roots may or may not be damaged . . . go to Stalk Damage Key B | |
| 3) Plants stunted, physically distorted, or with odd colors . . . go to Distorted Plant Damage Key | |
Specific Plant Part Damage Key - Select the best description from below:
1) Roots damaged . . . go to Root Damage Key
2) Seed damaged . . . go to Seed Damage Key
3) Stalk with tunneling, entrance or exit holes . . . go to Stalk Damage Key A
4) Leaf outside or within the whorl damaged . . . go to Leaf Damage Key A
5) Tassel with feeding damage . . . go to Tassel Damage Key
6) Silk, husk or kernels of ear damaged . . . go to Ear Damage Key
Seed Damage Key - Select the best description from below:
| 1) Plants not emerged: | |
| a) Larvae in soil at or near seed have legs (seed corn beetle, larva and adult, or wireworms) . . . go to Beetle Larvae Key | |
| b) Larvae in soil at or near seed have no legs . . . go to Seed corn maggot | |
| 2) Seedling plants cut off at or below ground (cutworms) . . . go to Cutworms Key | |
Root Damage Key - Select the best description from below:
1) Larvae in soil at or near roots have true legs only (wireworms, white grubs, cucumber beetle larvae) . . . go to Beetle Larvae Key
2) Larvae in soil at or near roots with both true legs and prolegs 
. . . go to Lesser cornstalk borer
Stalk Damage Key B - Select the best description from below:
| 1) Larvae or adults in stalk or in soil near plants have true legs only: | |
| a) Elongate body, legs 4-segmented with 1 claw . . . go to Wireworms | |
| b) Body with obvious 3 segments, legs 5-segmented with 2 claws . . . go to Red imported fire ants | |
| 2) Larvae in stalk or in soil near plants have
true legs and prolegs . . . go to Lessor cornstalk borer |
|
3) Larvae in stalk have no legs  . . . go to
Weevil Larvae Key |
|
Distorted Plant Damage Key - Select the best description from below:
1) Root damage with no external sign of leaf or stalk damage and no stalk tunneling (examine soil for wireworms, white grubs, cucumber beetle larvae) . . . go to Beetle Larvae Key
2) Stalk tunneling with or without minor leaf or external stalk damage . . . go to Stalk Tunneling Damage Key
3) Plants often distorted, leaves discolored, reduced ear production and distortion, possibly infected with virus disease transmitted by corn delphacid or leafhoppers . . . go to Leafhoppers and Planthoppers Key
4) Ear or whorl distorted, leaves not discolored, leaves may have rows of star-shaped punctures, look for presence of shield-shaped bugs . . . go to Stink Bugs Key
5) Leaves damaged or discolored . . . go to Damaged Leaves on Stunted Plants Key
Stalk Tunneling Damage Key - Select the best description from below:
1) Larvae in stalk have legs (southern cornstalk borer, European corn borer, lessor cornstalk borer). . . go to Moth Larvae Key
2) Larvae in stalk have no legs . . . go to Weevil Larvae Key
Damaged Leaves on Stunted Plants Key - Select the best description from below:
| 1) Yellowing or reddening of leaves or whorls, many small, red to black, flattened plant-sucking bugs on stem or in whorl. . . go to Chinch bugs | |
| 2) Leaves have bleached appearance from heavy feeding; look for abundant, very small beetles with shiny dark bodies and enlarged rear femora . . . go to Corn flea beetle | |
| 3) Emerging leaves and whorl tissue heavilly damaged: | |
| a) Whorl choked with light to medium brown colored frass (armyworms, corn earworms) . . . go to Armyworms and Earworms Key | |
| b) Whorl usually with short thread-like frass stuck to leaves; green with yellow or black beetles usually present (cucumber beetle adults) . . . go to Leaf Beetle Key. | |
Stalk Damage Key A - Select the best description from below:
| 1) Stalks broken . . . go to Broken Stalk Damage Key | |
| 2) Plants wilted or lodged, stalk with entry or puncture holes at or near base of plant, only base of stalk tunneled (3 to 4 inches above soil level), roots may or may not be damaged . . . go to Stalk Damage Key B | |
| 3) Plants stunted or distorted, stalk tunneling with or without minor leaf or external stalk damage: | |
| a) Larvae in stalk have legs (southern cornstalk borer, European corn borer, lessor cornstalk borer) . . . go to Moth Larvae Key | |
| b) Larvae in stalk have no legs . . . go to Weevil Larvae Key |
|
| 4) Plants with small holes chewed into stalks, some wilting possible, look for presence of beetles with head produced into broad, stout or long, narrow snout . . . go to Weevils Key | |
Broken Stalk Damage Key - Select the best description from below:
1) Larvae in stalk have legs (southern cornstalk borer, European cornborer) . . . go to Moth Larvae Key
2) Larvae in stalk have no legs . . . go to Weevil Larvae Key
Leaf Damage Key A - Select the best description from below:
1) Leaves with holes from chewing insects and stalks with tunneling . . . go to Stalk Damage Key A
2) Leaves with holes from chewing insects, or rows of star-shaped marks, and no stalk tunneling . . . go to Leaf Damage Key B
3) Leaves with bleached appearance or yellowish or reddish discoloration . . . go to Leaf Discoloration Key
4) Leaves within whorl with feeding damage . . . go to Whorl Feeding Damage Key
5) Leaves with linear mines; look for small fly larvae feeding between the top and bottom leaf surfaces (pupae also found within mines) . . . go to Corn blotch leafminer
Leaf Damage Key B - Select the best description from below:
| 1) Leaves with strips of feeding damage between the veins (look for very small caterpillars), rows of larger holes, or with irregular feeding damage at base of leaves . . . go to Armyworms and Earworms Key | |
| 2) Irregular pieces of leaves missing from edges and or center of leaves, insects with hardened bodies, 3 pairs of developed true legs: | |
| a) Dry, highly structured, pillow-shaped frass present on plants and on ground . . . go to Crickets and Grasshoppers Key | |
| b) Short and thread-like or groups of small particle frass stuck on leaves; soft-bodied, green with yellow or black beetles may or may not be present (cucumber beetle adults) . . . go to Leaf Beetle Key | |
| c) Leaves with notches chewed out of leaf edge; hard-bodied, grayish beetles with white markings on edge of wing covers may or may not be present . . . go to Whitefringed beetles | |
| 3) Leaves with rows of star-shaped marks, look for presence of shield-shaped bugs . . . go to Stink Bugs Key | |
Leaf Discoloration Key - Select the best description from below:
| 1) Leaves with yellow or reddish discoloration: | |
| a) Discoloration often present on newest leaves and in whorl; look for presence of abundant, small reddish to dark colored, flattened, plant -sucking insects on stalk, leaves or in whorl . . . go to Chinch bugs | |
| b) Discoloration usually widespread between the veins, may or may not be associated with stunted or distorted leaves, possibly virus diseases transmitted by corn delphacid or leafhoppers . . . go to Leafhoppers and Planthoppers Key | |
| 2) Leaves with bleached appearance: | |
| a) Look for abundant, very small beetles with shiny, dark bodies and enlarged rear femora feeding on leaves . . . go to Corn flea beetle | |
| b) Very small 6- to 8-legged,light to dark colored mites under leaves, usually associated with silken webs when damage becomes noticeable . . . go to Spider mites | |
Whorl Feeding Damage Key - Select the best description from below:
| 1) Emerging leaves with holes, not tied together with webbing: | |
| a) Caterpillars feeding on whorl tissue (armyworms, corn earworm, European corn borer, southern cornstalk borer, cutworms) . . . go to Moth Larvae Key | |
| b) Look for presence of short thread-like or groups of small-particle frass stuck to leaves; green with yellow or black beetles may or may not be present (cucumber beetles) . . . go to Leaf Beetle Key | |
| 2) Emerging leaves with or without holes or interveinal "window panes" and whorl leaves tied together with webbing . . . go to Grass leaftier | |
3) Whorl with very small, oval, dark colored
plant-sucking insects with tubes (cornicles) arising from near end of
abdomen  . . . go to Aphid Key |
|
Tassel Damage Key - Select the best description from below:
| 1) Anthers on tassel with pieces missing, frass usually present (chewing damage): | |
| a) Caterpillars feeding on tassel (armyworms, corn earworm) . . . go to Armyworms and Earworms Key | |
| b) Look for presence of short thread-like or small particle; green with yellow or black beetles may or may not be present (cucumber beetles) . . . go to Leaf Beetle Key | |
| 2) Tassel with very small, oval, dark colored
plant-sucking insects with tubes (cornicles) arising from near end of abdomen . . . go to
Aphid Key |
|
Ear Damage Key - Select the best description from below:
1) General ear distortion . . . go to Distorted Ear Damage Key
2) Silks damaged . . . go to Silk Damage Key
3) Husks damaged . . . go to Husk Damage Key
4) Kernels damaged . . . go to Kernel Damage Key A
Distorted Ear Damage Key - Select the best description from below:
1) Leaves may have star-shaped puncture wounds, but are not discolored; look for presence of shield-shaped bugs . . . go to Stink Bugs Key
2) Leaves likely discolored and whorl distorted possibly virus disease transmitted by corn delphacid or leafhoppers . . . go to Leafhoppers and Planthoppers Key
Silk Damage Key - Select the best description from below:
1) Caterpillars present in silk, or on husk, or in ear with visible ovoid-shaped frass (armyworms, corn earworm, cutworm) . . . go to Moth Larvae Key
2) Short, thread-like or small particle frass in silk or on surrounding husk; numerous silks clipped off; green, yellow or black beetles may or may not be present (cucumber beetle adults) . . . go to Leaf Beetle Key
3) Silks often matted, discolored, and damp in silk channel or at ear tip, white to yellowish, legless larvae with pointed head usually present in silk or in kernels . . . go to Corn silk fly larvae
4) Large, wide-bodied beetle that has legs with large spines usually found wedged into ear channel feeding on silks . . . go to Flower feeding scarab
5) Insects commonly found on or near silks, but not necessarily associated with obvious feeding damage . . . go to Other Pests on Ear Damage Key
Other Pests on Ear Damage Key - Select the best description from below:
1) Minute, elongate, usually light colored insects 
found on silks or between husk
leaves . . . go to Thrips
2) Greenish colored flies with several obvious dark colored bands across wings often observed beneath silks on husk . . . go to Corn silk fly
3) Very small, round to oval insects with short legs and
tubes
(cornicles) arising from
near rear of abdomen ; often associated with sticky honeydew in silk or on husk . . . go to
Aphid Key
Husk Damage Key - Select the best description from below:
1) Husks with round or oval holes often penetrating into ear (armyworms) . . . go to Armyworms and Earworms Key
2) Husks with irregular holes; leaves often with similar or more severe symptoms; dry, highly structured, pillow-shaped frass present on plants and on ground . . . go to Crickets and Grasshoppers Key
3) Large, wide bodied beetle with legs bearing large spines usually found with body wedged into armyworm hole in husk feeding on kernels . . . go to Flower feeding scarab
4) Insects commonly found on husks, but not necessarily associated with obvious feeding damage . . . go to Other Pests on Ear Damage Key
Kernel Damage Key A - Select the best description from below:
| 1) Kernels with chewing damage and larvae or adult insects present: | |
| a) Usually several kernels to large areas of ear
missing; large amounts of frass usually present; caterpillars with true legs and prolegs , usually
longer than 9/16 inch (armyworms, corn earworm, cutworms) . . . go to Moth Larvae Key |
|
| b) Single to many individual kernels damaged; larvae with worm-like body, true legs present or absent, no prolegs, less than 9/16 inch long . . . go to Kernel Damage Key B | |
| c) Adult beetles up to 1 inch long (sap beetles, darkling ground beetles, flower feeding scarabs, click beetles). . . go to Adult Beetle Key A | |
| 2) Kernels punctured through husk are sunken or popped, look for presence of shield-shaped bugs . . . go to Stink Bugs Key | |
Kernel Damage Key B - Select the best description from below:
| 1) Larvae in ear have no legs: | |
| a) Larvae feeding in ear have whitish to yellowish body that tapers to point at head from blunt-ended abdomen with two peg-like, rear-facing spiracles; larvae feed in moist corn usually 3 weeks old (pre-roasting stage) . . . go to Corn silk fly larvae | |
| b) Larvae feeding in ear are hump-backed with a whitish body and brown head; larvae usually feed on older, drier corn intended for sileage, seed or grain (post-milk stage) . . . go to Rice weevil larvae | |
| 2) Larvae in ear have true legs only, no prolegs: | |
| a) Soft-bodied larvae feeding in ear have light brown head, usually observed with many larvae per kernel; ear often with moist slime from fermenting kernels; adult beetles usually in company of larvae in ear . . . go to Sap beetle larvae | |
| b) Hard-bodied, elongate larvae feeding in ear have light brown head & thorax, and rear-facing projections on end of abdomen; feed on older, drier corn intended for sileage, seed or grain . . . go to Mealworms larvae | |
Weevil Larvae Key - Continue to select the best description from below:
1) Legless, ivory-colored, soft bodied larvae up to 1 1/4 in. long with hard yellow or brown heads; found in stalk or roots . . . go to Billbugs
2) Legless, translucent, soft-bodied larvae up to 3/4 in. long with long setae and hard dark brown heads; found in stalks . . . go to Corn stem weevil
Adult Beetle Key A - Select the best description from below:
| 1) Head produced into broad, stout or long, narrow snout with elbow-like antennae on narrowed portion of head . . . go to Weevils Key | |
| 2) Head not produced into snout: | |
| a) Wings at rest cover less than 75% of abdomen; oval-shaped, reddish-brown to black beetles less than 1/4 in. long . . . go to Sap beetles | |
| b) Wings at rest cover at least 80% of abdomen; body shape and color variable . . . go to Adult Beetle Key B | |
Weevils Key - Continue to select the best description from below:
| 1) Broad snout shorter than first thorcic segment; body 7/16 in. long; body grayish with white markings along outer edges of wing covers . . . go to Whitefringed beetle | |
| 2) Narow snout longer than first thorsaic segment: | |
| a) Body narrow and less than 3/16 in. long, reddish brown to black with yellow or reddish spots on the outside corners of the elytra; found in corn ears . . . go to Rice weevil | |
| b) Body 3/8 to 9/16 in. long with shiny black lines or bumps on elytra or thorax . . . go to Billbugs | |
| c) Body less than 3/8 in. long, brown body flecked with lighter colored scales . . . go to Corn stem weevil | |
Adult Beetle Key B - Select the best description from below (refer to 
for selections 1 through 4b):
| 1) Body tapering toward head and rear; underside of first thorcic segment with tooth-like projection protruding backward into groove in second thorcic segment; five tarsal segments on each leg ; found in whorls and leaf axils . . . go to Click beetle (Adult wireworm) | |
| 2) Body elongate, smooth, brown, 1/2 to 1 in. long; antennal segments bead-like; five tarsal segments on first two pairs of legs, but only four tarsal segments on third pair of legs; attracted to roasting stage corn; found in whorls and ears . . . go to Darkling ground beetle (adult mealworms) | |
| 3) Body heavy, stout, over 1/2 inch long; legs spiny; body with bright metallic colors; last several antennal segments expanded to form flattened club; five tarsal segments on each leg; found feeding on pollen on anthers, silk or kernels through bird or caterpillar-damaged husks . . . go to Flower feeding scarab | |
| 4) Body oval, smooth, somewhat flattened, less than 1/2 in. long; antennal segments longer than wide, not bead-like: | |
| a) Shiny, brown beetles; five tarsal segments on each leg; found in or on soil or leaf trash . . . go to Seedcorn beetle and Slender seedcorn beetle | |
| b) Shiny black, blue or green beetles; four tarsal segments on each leg; usually found feeding on plants . . . go to Leaf Beetle Key | |
Leaf Beetle Key - Select the best description from below:
1) Green, oval-shaped body with 12 black spots on elytra; black head and antennae . . . go to Spotted cucumber beetle
2) Green, oval-shaped body with four yellow to light greenish bars across elytra; red head and brown antennae . . . go to Banded cucumber beetle
3) Shiny, black or brightly colored (blue or green) body less than 1/4 in. long; legs same color or darker than body, with femora of rear legs enlarged for jumping . . . go to Flea beetles, including Corn flea beetle
Leafhoppers and Planthoppers Key - Select the best description from below:
| 1) Large, flattened spur at the apex of the tibia of the hind leg; compound eyes bead-like and arising from within cavities of head . . . go to Corn delphacid | |
| 2) No flattened spur at the apex of the tibia of the hind leg; ovoid- to triangular-shaped compound eyes appear to be nearly continuous with outline of head: | |
| a) Pale yellow to green-yellow body; two black spots on crown of head between compound eyes; rear margin of first thorsaic segment (prothorax) deeply indented to form inverted "V" shape . . . go to Corn leafhopper | |
| b) Body (and wing) color variable; four dark spots on crown of head between compound eyes; rear margin of prothorax only slightly and gradually indented . . . go to Blackfaced leafhopper | |
| c) Body (and wing) more or less gray . . . go to Gray lawn leafhopper | |
| d) Body (and wing) bright green; area above mouthparts and between compound eyes with three to four rows of blackish bars extending toward the center of the face and one bar running down toward mouthparts from near ocelli . . . go to Aster leafhopper | |
Crickets and Grasshoppers Key - Select the best description from below:
1) Oval-shaped opening on tibia of front legs; antennae usually as long as or longer than body; wings sharply bent downward at sides of body; long tube-like ovipositor; long paired cerci at end of abdomen . . . go to Field crickets
2) No oval-shaped opening on tibia of front legs, but auditory openings on sides of first abdominal segment; antennae shorter than 1/2 body length; ovipositor usually not visible at rest; cerci at end of abdomen very short if visible . . . go to Grasshoppers
Stink Bugs Key - Select the best description from below:
1) Adult bodies green; bodies of immatures green to black with white, green or pink markings; rounded spine on abdomen points forward between base of hind legs; antennae 5-segmented . . . go to Southern green stink bug
2) Brown, shield-shaped; lateral edges of pronotum expanded outward into broad, blunt points; antennae 5-segmented . . . go to Brown stink bug
Aphid Key - Select the best description from below:
1) Cornicles green with black ends and orange-red to red at base of cornicles and end of abdomen; body medium green . . . go to Birdcherry oat aphid
2) Cornicles black with green at base of cornicles and end of the abdomen; body light to medium green . . . go to Corn leaf aphid
Moth Larvae Key - Select the best description from below:
1) Pink to light brown to gray with faint spots on back and creme colored underside; found feeding in whorl and inside leaves and stems . . . go to European corn borer
2) White with prominent dark spots on each throasic and abdominal segment; found inside corn stems . . . go to Southern cornstalk borer
3) Banded with bluish, reddish-purple, and creme; usually found in stem or below soil near soil covered silken tubes . . . go to Lesser cornstalk borer
4) Shiny, medium green to medium brown with medium brown, flattened head; mouthparts face nearly forward; usually found among whorl leaves that have been tied together with tough, silken bands spaced 3/8 to 3/4" apart . . . go to Grass leaftier
5) Sutures on front of head (face) forming an inverted
"Y" 
; feed on foliage in whorl, on tassel and on all parts of ears . . . go to Armyworms and
Earworms Key
6) Sutures on front of head (face) forming an inverted "V"; feed on foliage mostly by night and hide during the day; curl up tightly when handled . . . go to Cutworms Key
| 1) Skin (cuticle) somewhat rough, covered with microspines; light green to pink to brown with alternating light and dark stripes; head light brown with netlike pattern . . . go to Corn earworm | |
| 2) Skin smooth, lacking microspines: | |
| a) Prominent white inverted "Y" on face; four to six large (larger than spiracles) dark bumps (tubercles) on top of all thorcic and abdominal segments, four on top of eighth abdominal segment prominent; sides of body light green to tan to dark brown with slightly lighter color on back . . . go to Fall armyworm | |
| b) Inverted "Y" on face not prominent or white; light and dark stripe above the spiracles and another light stripe below the spiracles all run the length of the body; usually a dark spot above these lines on second thorcic segment; tubercles smaller than spiracles; body light to dark green to nearly black . . . go to Beet armyworm | |
| c) Inverted "Y" on face not prominent or white; humpacked appearance greatest at first abdominal segment; body often very colorful with light to reddish-brown head; narrow white to orange stripe down the center of the back; a yellowish to orange broad band runs backward from first abdominal segment below the spiracles; some to all abdominal and some thorcic segments have dark triangular markings near the center of the back . . . go to Southern armyworm | |
Cutworms Key - Select the best description from below:
1) Two rows of black raised bumps (tubercles) run down the top of the back; skin (cuticle) covered with small and large granules; color ranges from light gray to black on back and lighter below . . . go to Black cutworm
2) Top of back gray and flecked with irregular dark brown pigmentation; undersurface of body flecked with white; granules on cuticle are isolated, blunt and pointing slightly backward . . . go to Granulate cutworm
3) Top of back medium gray and lighter below; a row of yellow circular spots runs down back (particularly on third throasic and first three abdominal segments); cuticle smooth without granulation . . . go to Variegated cutworm
Beetle Larvae Key - Select the best description from below:
1) Elongate, wormlike with hard body; orangish-brown to brown; short legs with 5 or more segments and a claw; end of abdomen may be rounded or with numerous tooth-like projections; no hardened, raised (sometimes with teeth or ridges) area (mola) near base of mandible (need to pull mandibles apart to go to this last character) . . . go to Seedcorn beetle or Slender seedcorn beetle
2) Elongate, wormlike with hard body; orangish-brown to brown; short legs with 4 or fewer segments and a claw; end of abdomen may be rounded or with numerous tooth-like projections; no mola near base of mandible . . . go to Wireworms
3) C-shaped, whitish grub with dark head and rounded end of abdomen with numerous hairs; long hardened legs . . . go to White grub
4) Elongate, worm-like with soft, whitish body and dark head short legs; tooth-like projections at end of abdomen . . . go to Banded cucumber beetle or Spotted cucumber beetle